=Experiment.=–Use the same or a similar set of tubes as in the

experiment illustrated in Fig. 23. Fill the tubes with the same kinds

of dry sifted soils. Then pour water into the pan or dish beneath the

tubes until it rises a quarter of an inch above the lower end of the

tubes (Fig. 24). Watch the water rise in the soils. The water will be

found to rise rapidly in the sand about two or three inches and then

stop or continue very slowly a short distance further. In the clay it

starts very slowly, but after several hours is finally carried to the

top of the soil. The organic matter takes it up less rapidly than the

sand, faster than the clay, and finally carries it to the top. By this

and further experiments it will be found that the power of soils to

take moisture from below depends on their texture or the size and

closeness of their particles.

We found the sand pumped the water only a short distance and then

stopped.

What can we do for our sandy soils to give them greater power to take

moisture from below? For immediate results we can compact them by

rolling or packing. This brings the particles closer together, makes

the spaces between them smaller, and therefore allows the water to

climb higher. For more lasting results we can fill them with organic

matter in the shape of stable manures or crops turned under. Clay may

be used, but is expensive to haul.

Which soils have greatest power to hold the water which enters them?

=Experiment.=–Use the same or similar apparatus as for the last

experiment. After placing the cloth caps over the ends of the tubes

label and carefully weigh each one, keeping a record of each; then

fill them with the dry soils and weigh again. Now place the tubes in

the rack and pour water in the upper ends until the entire soil is

wet; cover the tops and allow the surplus water to drain out; when the

dripping stops, weigh the tubes again, and by subtraction find the

amount of water held by the soil in each tube; compute the percentage.

It will be found that the organic matter will hold a much larger

percentage of water than the other soils; and the clay more than the

sand. The tube of organic soil will actually hold a larger amount of

water than the other tubes. (See also Fig. 25.)

In the experiment on page 40 we noticed that the sand took in the

water poured on its surface and let it run through very quickly. This

is a fault of sandy soils.

What can we do for our sandy soils to help them to hold better the

moisture which falls on them and tends to leach through them? For

immediate effect we can close the pores somewhat by compacting the

soil with the roller. For more lasting effects, we can fill them with

organic matter.

Which soils will hold longest the water which they have absorbed? Or

which soils will keep moist longest in dry weather?

[Illustration: FIG. 23.

To show how bottles may be used in place of lamp chimneys shown in

Figs 22 and 24.]

[Illustration: FIG. 24.--CAPILLARITY OF SOILS

To show the relative powers of soils to take water from below.]

[Illustration: FIG. 25.--WATER-ABSORBING AND WATER-HOLDING POWERS OF

SOILS.]

=Experiment.=–Fill a pan or bucket with moist sand, another with

moist clay, and a third with moist organic matter; set them in the sun

to dry and notice which dries last. The organic matter will be found

to hold moisture much longer than the other soils. The power of the

other soils to hold moisture through dry weather can be improved by

mixing organic matter with them.

We find then that the power of soils to absorb and hold moisture

depends on the amount of sand, clay, or humus which they contain, and

the compactness of the particles. We see also how useful organic

matter is in improving sandy and clayey soils.

=Experiment.=–Use the same or a similar set of tubes as in the

experiment illustrated in Fig. 23. Fill the tubes with the same kinds

of dry sifted soils. Then pour water into the pan or dish beneath the

tubes until it rises a quarter of an inch above the lower end of the

tubes (Fig. 24). Watch the water rise in the soils. The water will be

found to rise rapidly in the sand about two or three inches and then

stop or continue very slowly a short distance further. In the clay it

starts very slowly, but after several hours is finally carried to the

top of the soil. The organic matter takes it up less rapidly than the

sand, faster than the clay, and finally carries it to the top. By this

and further experiments it will be found that the power of soils to

take moisture from below depends on their texture or the size and

closeness of their particles.

We found the sand pumped the water only a short distance and then

stopped.

What can we do for our sandy soils to give them greater power to take

moisture from below? For immediate results we can compact them by

rolling or packing. This brings the particles closer together, makes

the spaces between them smaller, and therefore allows the water to

climb higher. For more lasting results we can fill them with organic

matter in the shape of stable manures or crops turned under. Clay may

be used, but is expensive to haul.

Which soils have greatest power to hold the water which enters them?

=Experiment.=–Use the same or similar apparatus as for the last

experiment. After placing the cloth caps over the ends of the tubes

label and carefully weigh each one, keeping a record of each; then

fill them with the dry soils and weigh again. Now place the tubes in

the rack and pour water in the upper ends until the entire soil is

wet; cover the tops and allow the surplus water to drain out; when the

dripping stops, weigh the tubes again, and by subtraction find the

amount of water held by the soil in each tube; compute the percentage.

It will be found that the organic matter will hold a much larger

percentage of water than the other soils; and the clay more than the

sand. The tube of organic soil will actually hold a larger amount of

water than the other tubes. (See also Fig. 25.)

In the experiment on page 40 we noticed that the sand took in the

water poured on its surface and let it run through very quickly. This

is a fault of sandy soils.

What can we do for our sandy soils to help them to hold better the

moisture which falls on them and tends to leach through them? For

immediate effect we can close the pores somewhat by compacting the

soil with the roller. For more lasting effects, we can fill them with

organic matter.

Which soils will hold longest the water which they have absorbed? Or

which soils will keep moist longest in dry weather?

[Illustration: FIG. 23.

To show how bottles may be used in place of lamp chimneys shown in

Figs 22 and 24.]

[Illustration: FIG. 24.--CAPILLARITY OF SOILS

To show the relative powers of soils to take water from below.]

[Illustration: FIG. 25.--WATER-ABSORBING AND WATER-HOLDING POWERS OF

SOILS.]

=Experiment.=–Fill a pan or bucket with moist sand, another with

moist clay, and a third with moist organic matter; set them in the sun

to dry and notice which dries last. The organic matter will be found

to hold moisture much longer than the other soils. The power of the

other soils to hold moisture through dry weather can be improved by

mixing organic matter with them.

We find then that the power of soils to absorb and hold moisture

depends on the amount of sand, clay, or humus which they contain, and

the compactness of the particles. We see also how useful organic

matter is in improving sandy and clayey soils.

THE EFFECT OF WORKING SOILS WHEN WET

By this time the soils we left in the pans (see page 26), sand, clay,

humus and garden soil, must be dry. If so, examine them. We find that

the clay which was stirred when wet has dried into an almost bricklike

mass, while that which was not stirred is not so hard, though it has a

thick, hard crust. The sand is not much affected by stirring when wet.

The organic matter which was stirred when wet has perhaps stiffened a

little, but very easily crumbles; the unstirred part was not much

affected by the wetting and drying.

The garden soil after drying is not as stiff as the clay nor as loose

as the sand and humus. This is because it is very likely a mixture of

all three, the sand and the humus checking the baking. This teaches

us that it is not a good plan to work soils when they are wet if they

are stiff and sticky; and that our stiff clay soils can be kept from

drying hard or baking by the use of organic matter. “And that’s a

witness” for organic matter.

The relation of the soil to moisture is very important, for moisture

is one of the greatest factors if not the greatest in the growth of

the crop.

The power to absorb or soak up moisture from any source is greatest in

those soils whose particles are smaller and fit closer together.

It is for this reason that strong loams and clay soils absorb and hold

three times as much water as sandy soils do, while peaty or humus

soils absorb a still larger proportion.

The reason why crops burn up so quickly on sandy soils during dry

seasons is because of their weak power to hold water.

The clay and humus soils carry crops through dry weather better

because of their power to hold moisture and to absorb or soak up

moisture from below. It is for this reason also that clay and peaty

soils more often need draining than sandy soils.

When rain falls on a sandy soil it enters readily, but it is apt to

pass rapidly down and be, to a great extent, lost in the subsoil, for

the sand has not sufficient power to hold much of it.

When rain falls on a clay soil it enters less readily because of the

closeness of the particles, and during long rains or heavy showers

some of the water may run off the surface. If the surface has been

recently broken and softened with the plow or cultivator the rain

enters more readily. What does enter is held and is not allowed to run

through as in the case of the sand.

Humus soil absorbs the rain as readily as the sand and holds it with a

firmer grip than clay.

This fact gives us a hint as to how we may improve the sand and clay.

Organic matter mixed with these soils by applying manures or plowing

under green crops will cause the sand to hold the rain better and the

clay to absorb it more readily.

CHAPTER V

FORMS OF SOIL WATER

Water which comes to the soil and is absorbed exists in the soil

principally in two forms: Free water and capillary water.

FREE WATER

Free water is that form of water which fills our wells, is found in

THE EFFECT OF WORKING SOILS WHEN WET

By this time the soils we left in the pans (see page 26), sand, clay,

humus and garden soil, must be dry. If so, examine them. We find that

the clay which was stirred when wet has dried into an almost bricklike

mass, while that which was not stirred is not so hard, though it has a

thick, hard crust. The sand is not much affected by stirring when wet.

The organic matter which was stirred when wet has perhaps stiffened a

little, but very easily crumbles; the unstirred part was not much

affected by the wetting and drying.

The garden soil after drying is not as stiff as the clay nor as loose

as the sand and humus. This is because it is very likely a mixture of

all three, the sand and the humus checking the baking. This teaches

us that it is not a good plan to work soils when they are wet if they

are stiff and sticky; and that our stiff clay soils can be kept from

drying hard or baking by the use of organic matter. “And that’s a

witness” for organic matter.

The relation of the soil to moisture is very important, for moisture

is one of the greatest factors if not the greatest in the growth of

the crop.

The power to absorb or soak up moisture from any source is greatest in

those soils whose particles are smaller and fit closer together.

It is for this reason that strong loams and clay soils absorb and hold

three times as much water as sandy soils do, while peaty or humus

soils absorb a still larger proportion.

The reason why crops burn up so quickly on sandy soils during dry

seasons is because of their weak power to hold water.

The clay and humus soils carry crops through dry weather better

because of their power to hold moisture and to absorb or soak up

moisture from below. It is for this reason also that clay and peaty

soils more often need draining than sandy soils.

When rain falls on a sandy soil it enters readily, but it is apt to

pass rapidly down and be, to a great extent, lost in the subsoil, for

the sand has not sufficient power to hold much of it.

When rain falls on a clay soil it enters less readily because of the

closeness of the particles, and during long rains or heavy showers

some of the water may run off the surface. If the surface has been

recently broken and softened with the plow or cultivator the rain

enters more readily. What does enter is held and is not allowed to run

through as in the case of the sand.

Humus soil absorbs the rain as readily as the sand and holds it with a

firmer grip than clay.

This fact gives us a hint as to how we may improve the sand and clay.

Organic matter mixed with these soils by applying manures or plowing

under green crops will cause the sand to hold the rain better and the

clay to absorb it more readily.

CHAPTER V

FORMS OF SOIL WATER

Water which comes to the soil and is absorbed exists in the soil

principally in two forms: Free water and capillary water.

FREE WATER

Free water is that form of water which fills our wells, is found in

the bottoms of holes dug in the ground during wet seasons and is often

found standing on the surface of the soil after heavy or long

continued rains. It is sometimes called ground water or standing water

and flows under the influence of gravity.

Is free water good for the roots of farm plants? If we remember how

the root takes its food and moisture, namely through the delicate root

hairs; and also remember the experiment which showed us that roots

need air, we can readily see that free water would give the root hairs

enough moisture, but it would at the same time drown them by cutting

off the air. Therefore free water is not directly useful to the roots

of house plants or farm plants, excepting such as are naturally

swamp plants, like rice, which grows part of the time with its

roots covered with free water.

[Illustration: FIG. 26.--CAPILLARY TUBES.

To show how water rises in small tubes or is drawn into small spaces.]

[Illustration: FIG. 27.--CAPILLARY PLATES.

Water is drawn to the highest point where the glass plates are closest

together.]

[Illustration: FIG. 28.

A cone of soil to show capillarity. Water poured about the base of

this cone of soil has been drawn by capillary force half-way to the

top.]

[Illustration: FIG. 29.

To show the relative amounts of film-moisture held by coarse and fine

soils. The colored water in bottle _A_ represents the amount of water

required to cover the half pound of pebbles in the tumbler _B_ with a

film of moisture. The colored water in bottle _C_ shows the amount

required to cover the soil grains in the half pound of sand in tumbler

_D._]

CAPILLARY WATER

If you will take a number of glass tubes of different sizes, the

largest not more than one-fourth of an inch in diameter, and hold them

with one end of each in water or some colored liquid, you will notice

that the water rises in the tubes (Fig. 26), and that it rises highest

in the smallest tube. The force which causes the water to rise in

these tubes is called the capillary force, from the old Latin word

_capillum_ (a hair), because it is most marked in hair-like tubes, the

smaller the tube the higher the water will rise. The water which rises

in the tubes is called capillary water.

Another method of illustrating capillary water is to tie or hold

together two flat pieces of glass, keeping two of the edges close

together and separating the opposite two about one-eighth of an inch

with a sliver of wood. Then set them in a plate of water or colored

liquid and notice how the water rises between the pieces of glass,

rising higher the smaller the space (Fig. 27). It is the capillary

force which causes water to rise in a piece of cloth or paper dipped

in water.

Take a plate and pour onto it a cone-shaped pile of dry sand or fine

soil; then pour water around the base of the pile and note how the

water is drawn up into the soil by capillary force (Fig. 28).

Capillary water is the other important form of water in the soil. This

is moisture which is drawn by capillary force or soaks into the spaces

between the soil particles and covers each particle with a thin film

of moisture.

FILM WATER

Take a marble or a pebble, dip it into water and notice the thin layer

or film of water that clings to it. This is a form of capillary water

and is sometimes called film water or film moisture. Take a handful of

soil that is moist but not wet, notice that it does not wet the hand,

and yet there is moisture all through it; each particle is covered

with a very thin film of water.

the bottoms of holes dug in the ground during wet seasons and is often

found standing on the surface of the soil after heavy or long

continued rains. It is sometimes called ground water or standing water

and flows under the influence of gravity.

Is free water good for the roots of farm plants? If we remember how

the root takes its food and moisture, namely through the delicate root

hairs; and also remember the experiment which showed us that roots

need air, we can readily see that free water would give the root hairs

enough moisture, but it would at the same time drown them by cutting

off the air. Therefore free water is not directly useful to the roots

of house plants or farm plants, excepting such as are naturally

swamp plants, like rice, which grows part of the time with its

roots covered with free water.

[Illustration: FIG. 26.--CAPILLARY TUBES.

To show how water rises in small tubes or is drawn into small spaces.]

[Illustration: FIG. 27.--CAPILLARY PLATES.

Water is drawn to the highest point where the glass plates are closest

together.]

[Illustration: FIG. 28.

A cone of soil to show capillarity. Water poured about the base of

this cone of soil has been drawn by capillary force half-way to the

top.]

[Illustration: FIG. 29.

To show the relative amounts of film-moisture held by coarse and fine

soils. The colored water in bottle _A_ represents the amount of water

required to cover the half pound of pebbles in the tumbler _B_ with a

film of moisture. The colored water in bottle _C_ shows the amount

required to cover the soil grains in the half pound of sand in tumbler

_D._]

CAPILLARY WATER

If you will take a number of glass tubes of different sizes, the

largest not more than one-fourth of an inch in diameter, and hold them

with one end of each in water or some colored liquid, you will notice

that the water rises in the tubes (Fig. 26), and that it rises highest

in the smallest tube. The force which causes the water to rise in

these tubes is called the capillary force, from the old Latin word

_capillum_ (a hair), because it is most marked in hair-like tubes, the

smaller the tube the higher the water will rise. The water which rises

in the tubes is called capillary water.

Another method of illustrating capillary water is to tie or hold

together two flat pieces of glass, keeping two of the edges close

together and separating the opposite two about one-eighth of an inch

with a sliver of wood. Then set them in a plate of water or colored

liquid and notice how the water rises between the pieces of glass,

rising higher the smaller the space (Fig. 27). It is the capillary

force which causes water to rise in a piece of cloth or paper dipped

in water.

Take a plate and pour onto it a cone-shaped pile of dry sand or fine

soil; then pour water around the base of the pile and note how the

water is drawn up into the soil by capillary force (Fig. 28).

Capillary water is the other important form of water in the soil. This

is moisture which is drawn by capillary force or soaks into the spaces

between the soil particles and covers each particle with a thin film

of moisture.

FILM WATER

Take a marble or a pebble, dip it into water and notice the thin layer

or film of water that clings to it. This is a form of capillary water

and is sometimes called film water or film moisture. Take a handful of

soil that is moist but not wet, notice that it does not wet the hand,

and yet there is moisture all through it; each particle is covered

with a very thin film of water.

Now this film water is just the form of water that can supply the very

slender root hairs without drowning them, that is, without keeping the

air from them. And the plant grower should see to it that the roots of

his plants are well supplied with film water and are not drowned by

the presence of free water. Capillary water may sometimes completely

fill the spaces between the soil particles; when this occurs the roots

are drowned just as in the case of free water as we saw when cuttings

were placed in the puddled clay (see Fig. 18). Free water is

indirectly of use to the plant because it serves as a supply for

capillary and film moisture.

Now I think we can answer the question which was asked when we were

studying the habit of growth of roots but was left unanswered at the

time (see page 14). The question was this: Of what value is it to the

farmer to know that roots enter the soil to a depth of three to six

feet? We know that roots will not grow without air. We also know that

if the soil is full of free water there is no air in it, and,

therefore, roots of most plants will not grow in it. It is, therefore,

of interest to the farmer to see that free water does not come within

at least three or four feet of the surface of the soil so that the

roots of his crops may have plenty of well ventilated soil in which to

develop. If there is a tendency for free water to fill the soil a

large part of the time, the farmer can get rid of it by draining the

land. We get here a lesson for the grower of house plants also. It is

that we must be careful that the soil in the pots or boxes in which

our plants are growing is always supplied with film water and not wet

and soggy with free water. Water should not be left standing long in

the saucer under the pot of a growing plant. It is best to water the

pot from the top and let the surplus water drain into the saucer and

then empty it out.

Which soils have the greatest capacity for film water?

=Experiment.=–Place in a tumbler or bottle one-half pound of pebbles

about the size of a pea or bean; pour a few drops of water on them and

shake them; continue adding water and shaking them till every pebble

is covered with a film of water; let any surplus water drain off. Then

weigh again; the difference in the two weights will be approximately

the weight of the film water that the pebbles can carry. Repeat this

with sand and compare the two amounts of water. A striking

illustration can be made by taking two slender bottles and placing in

them amounts of colored water equal to the amounts of film water held

by the pebbles and sand respectively. In the accompanying illustration

(Fig. 29), _A_ represents the amount of water that was found necessary

to cover the pebbles in tumbler _B_ with a film of moisture. _C_ is

the amount that was necessary to cover with a film the particles of

sand in _D_. The finer soil has the greater area for film moisture. It

has been estimated that the particles of a cubic foot of clay loam

have a possible aggregate film surface of three-fourths of an acre.

CHAPTER VI

LOSS OF SOIL WATER

LOSS OF SOIL WATER AND MEANS OF CHECKING THE LOSS

We noticed in previous paragraphs that soil might at times have too

much water in it for proper ventilation and so check the growth of the

roots of the plant. Now is it possible that soil water may be lost or

wasted and if so can we check the loss?

In the experiment to find out how well the soils would take in the

rainfall (page 40) we noticed that the clay soil took in the water

very slowly and that on a field of clay soil part of the rain water

would be likely to run off over the surface and be lost. Free water

may be lost then, by surface wash.

We noticed methods of checking this loss, namely, pulverizing the soil

with the tillage tools and putting organic matter into it to make it

absorb the rain more readily.

Now this film water is just the form of water that can supply the very

slender root hairs without drowning them, that is, without keeping the

air from them. And the plant grower should see to it that the roots of

his plants are well supplied with film water and are not drowned by

the presence of free water. Capillary water may sometimes completely

fill the spaces between the soil particles; when this occurs the roots

are drowned just as in the case of free water as we saw when cuttings

were placed in the puddled clay (see Fig. 18). Free water is

indirectly of use to the plant because it serves as a supply for

capillary and film moisture.

Now I think we can answer the question which was asked when we were

studying the habit of growth of roots but was left unanswered at the

time (see page 14). The question was this: Of what value is it to the

farmer to know that roots enter the soil to a depth of three to six

feet? We know that roots will not grow without air. We also know that

if the soil is full of free water there is no air in it, and,

therefore, roots of most plants will not grow in it. It is, therefore,

of interest to the farmer to see that free water does not come within

at least three or four feet of the surface of the soil so that the

roots of his crops may have plenty of well ventilated soil in which to

develop. If there is a tendency for free water to fill the soil a

large part of the time, the farmer can get rid of it by draining the

land. We get here a lesson for the grower of house plants also. It is

that we must be careful that the soil in the pots or boxes in which

our plants are growing is always supplied with film water and not wet

and soggy with free water. Water should not be left standing long in

the saucer under the pot of a growing plant. It is best to water the

pot from the top and let the surplus water drain into the saucer and

then empty it out.

Which soils have the greatest capacity for film water?

=Experiment.=–Place in a tumbler or bottle one-half pound of pebbles

about the size of a pea or bean; pour a few drops of water on them and

shake them; continue adding water and shaking them till every pebble

is covered with a film of water; let any surplus water drain off. Then

weigh again; the difference in the two weights will be approximately

the weight of the film water that the pebbles can carry. Repeat this

with sand and compare the two amounts of water. A striking

illustration can be made by taking two slender bottles and placing in

them amounts of colored water equal to the amounts of film water held

by the pebbles and sand respectively. In the accompanying illustration

(Fig. 29), _A_ represents the amount of water that was found necessary

to cover the pebbles in tumbler _B_ with a film of moisture. _C_ is

the amount that was necessary to cover with a film the particles of

sand in _D_. The finer soil has the greater area for film moisture. It

has been estimated that the particles of a cubic foot of clay loam

have a possible aggregate film surface of three-fourths of an acre.

CHAPTER VI

LOSS OF SOIL WATER

LOSS OF SOIL WATER AND MEANS OF CHECKING THE LOSS

We noticed in previous paragraphs that soil might at times have too

much water in it for proper ventilation and so check the growth of the

roots of the plant. Now is it possible that soil water may be lost or

wasted and if so can we check the loss?

In the experiment to find out how well the soils would take in the

rainfall (page 40) we noticed that the clay soil took in the water

very slowly and that on a field of clay soil part of the rain water

would be likely to run off over the surface and be lost. Free water

may be lost then, by surface wash.

We noticed methods of checking this loss, namely, pulverizing the soil

with the tillage tools and putting organic matter into it to make it

absorb the rain more readily.

We noticed that water poured on the sand ran through it very quickly

and was apt to be lost by leaching or percolation. This we found could

be checked by rolling the soil and by putting organic matter into it

to close the pores.

We learned that roots take water from the soil for the use of the

plant and send it up to the leaves, which in turn send it out into the

air, or transpire it, as this process is called. We learned also that

the amount transpired is very great. Now water that is pumped up and

transpired by the crops we are growing we consider properly used. But

when weeds grow with the crop and pump and transpire water we consider

this water as lost or wasted.

Water may be lost then by being pumped up and transpired by weeds. And

this is the way weeds do their greatest injury to crops during dry

weather. The remedy is easily pointed out. Kill the weeds or do not

let them get a start.

There is another way, which we are not apt to notice, by which water

may be lost from the soil. When the soil in the pans in a previous

experiment (page 26) had been wet and set aside a few days it became

very dry. How did the water get out of this soil? That at the surface

of the soil evaporated or was changed into vapor and passed into the

air. Then water from below the surface was pumped up by capillary

force to take its place just as the water was pumped up in the tubes

of soil. This in turn was evaporated and the process repeated till all

of the water in the soil had passed into the air. Now this process is

going on in the field whenever it is not raining or the ground is not

frozen very hard.

Water then may be lost by evaporation.

How can we check this loss?

Suppose we try the experiment of covering the soil with some material

that cannot pump water readily.

=Experiment.=–Take four glass fruit jars, two-quart size, with

straight sides. If you cannot get them with straight sides cut off the

tops with a hot iron just below the shoulder; tin pails will do if the

glass jars cannot be had. Fill these with moist soil from the field or

garden, packing it till it is as hard as the unplowed or unspaded

soil. Leave one of them in this condition; from two of them remove an

inch or two of soil and replace it in the case of one with clean, dry,

coarse sand, and in the case of the other with chaff or straw cut into

half-inch lengths. Stir the soil in the fourth one to a depth of one

inch, leaving it light and crumbly. Now weigh the jars and set them

aside. Weigh each day for several days. The four jars illustrated in

Fig. 30 were prepared in this way and allowed to stand seven days. In

that time they lost the following amounts of water:

Amounts of water lost from jars of prepared soil in seven days.

No. 1 packed soil–lost 5.5 oz. equal to about 75 tons per acre.

No. 2 covered with straw–lost 2 oz. equal to about 27 tons per acre.

No. 3 covered with dry sand–lost 0 oz. equal to about tons per acre.

No. 4 covered with crumbled soil–lost 2.5 oz., equal to about 34 tons

per acre.

Why did not 2, 3 and 4 lose as much water as No. 1?

The soil in jar No. 1 was packed and water was pumped to the surface

by capillary force and was evaporated as fast as it came to the

surface.

In No. 2 the water could rise rapidly until it reached the straw, then

it was stopped almost entirely. But the straw being coarse, the air

circulated in it more or less freely and there was a slow loss by

evaporation. In jar No. 3 the water could rise only to the sand, which

was so coarse that the water could not climb on it to the surface, and

the air circulated in the sand so slowly that there was not sufficient

We noticed that water poured on the sand ran through it very quickly

and was apt to be lost by leaching or percolation. This we found could

be checked by rolling the soil and by putting organic matter into it

to close the pores.

We learned that roots take water from the soil for the use of the

plant and send it up to the leaves, which in turn send it out into the

air, or transpire it, as this process is called. We learned also that

the amount transpired is very great. Now water that is pumped up and

transpired by the crops we are growing we consider properly used. But

when weeds grow with the crop and pump and transpire water we consider

this water as lost or wasted.

Water may be lost then by being pumped up and transpired by weeds. And

this is the way weeds do their greatest injury to crops during dry

weather. The remedy is easily pointed out. Kill the weeds or do not

let them get a start.

There is another way, which we are not apt to notice, by which water

may be lost from the soil. When the soil in the pans in a previous

experiment (page 26) had been wet and set aside a few days it became

very dry. How did the water get out of this soil? That at the surface

of the soil evaporated or was changed into vapor and passed into the

air. Then water from below the surface was pumped up by capillary

force to take its place just as the water was pumped up in the tubes

of soil. This in turn was evaporated and the process repeated till all

of the water in the soil had passed into the air. Now this process is

going on in the field whenever it is not raining or the ground is not

frozen very hard.

Water then may be lost by evaporation.

How can we check this loss?

Suppose we try the experiment of covering the soil with some material

that cannot pump water readily.

=Experiment.=–Take four glass fruit jars, two-quart size, with

straight sides. If you cannot get them with straight sides cut off the

tops with a hot iron just below the shoulder; tin pails will do if the

glass jars cannot be had. Fill these with moist soil from the field or

garden, packing it till it is as hard as the unplowed or unspaded

soil. Leave one of them in this condition; from two of them remove an

inch or two of soil and replace it in the case of one with clean, dry,

coarse sand, and in the case of the other with chaff or straw cut into

half-inch lengths. Stir the soil in the fourth one to a depth of one

inch, leaving it light and crumbly. Now weigh the jars and set them

aside. Weigh each day for several days. The four jars illustrated in

Fig. 30 were prepared in this way and allowed to stand seven days. In

that time they lost the following amounts of water:

Amounts of water lost from jars of prepared soil in seven days.

No. 1 packed soil–lost 5.5 oz. equal to about 75 tons per acre.

No. 2 covered with straw–lost 2 oz. equal to about 27 tons per acre.

No. 3 covered with dry sand–lost 0 oz. equal to about tons per acre.

No. 4 covered with crumbled soil–lost 2.5 oz., equal to about 34 tons

per acre.

Why did not 2, 3 and 4 lose as much water as No. 1?

The soil in jar No. 1 was packed and water was pumped to the surface

by capillary force and was evaporated as fast as it came to the

surface.

In No. 2 the water could rise rapidly until it reached the straw, then

it was stopped almost entirely. But the straw being coarse, the air

circulated in it more or less freely and there was a slow loss by

evaporation. In jar No. 3 the water could rise only to the sand, which

was so coarse that the water could not climb on it to the surface, and

the air circulated in the sand so slowly that there was not sufficient

evaporation to affect scales weighing to one-quarter ounce. No. 4 lost

less than No. 1 because, as in the case of the sand, the water could

not climb rapidly to the surface on the coarse crumbs of soil. The

loss that did take place from No. 4 was what the air took from the

loosely stirred soil on the surface with a very little from the lower

soil. Simply stirring the surface of the sod in No. 4 reduced the loss

of water to less than half the loss from the hard soil in No. 1.

This experiment gives us the clew to the method of checking loss of

water from the soil by evaporation. It is to keep the water from

climbing up to the surface, or check the power of the soil to pump the

water to the surface by making it loose on top. This loose soil is

called a soil mulch. Everything that we do to the soil that loosens

and crumbles the surface tends to check the loss of water by

evaporation from the soil below.

[Illustration: FIG. 30.--TO SHOW THE EFFECT OF A SOIL MULCH

1. Packed soil, lost in 7 days 5.5 ozs. water, equal to 75 tons per

acre.

2. Packed soil, covered with straw, lost in 7 days 2 ozs. water, equal

to 27 tons per acre.

3. Packed soil, covered with sand, lost in 7 days 0 ozs. water, equal to

tons per acre.

4. Packed soil, covered with soil mulch, lost in 7 days 2.5 ozs.

water, equal to 34 tons per acre.]

CHAPTER VII

SOIL TEMPERATURE

We learned that roots need heat for their growth and development. Now

what is the relation of the different kinds of soil toward heat or

what are their relative powers to absorb and hold heat?

=Experiment.=–Some days before this experiment, spread on a dry floor

about a half bushel each of sand, clay and decayed leaf mould or black

woods soil. Stir them occasionally till they are thoroughly dry. When

they are dry place them separately in three boxes or large flower pots

and keep dry. In three similar boxes or pots place wet sand, wet clay,

and wet humus. Place a thermometer in each of the soils, placing the

bulb between one and two inches below the surface (Fig. 31). Then

place the soils out of doors where the sun can shine on them and leave

them several days. If a rain should come up protect the dry soils.

Observe and make a record of the temperatures of each soil several

times a day. Chart the average of several days observations. Fig. 32

shows the averages of several days observations on a certain set of

soils.

It will be noticed that the temperature of the soils increased until

the early part of the afternoon and after that time they lost heat.

[Illustration: FIG. 31.--SOIL TEMPERATURE EXPERIMENT.

Thermometer in pot of soil.]

HOW SOILS ARE WARMED

=Experiment.=–Hold your hand in bright sunlight or near a warm stove

or radiator. Your hand is warmed by heat radiated from the sun or warm

stove through the air to your body. In the same manner the rays of the

sun heat the surface of the soil.

=Experiment.=–Take the stove poker or any small iron rod and hold one

end of it in the fire or hold one end of a piece of wire in a candle

or lamp flame. The end of the rod or wire will quickly become very hot

and heat will gradually be carried its entire length until it becomes

too hot to hold. This carrying of the heat from particle to particle

through the length of the rod is called heating by conduction. Now

when the warm rays of the sun reach the soil, or a warm wind blows

over it, the surface particles are warmed and then pass the heat on to

the next ones below, and these in turn pass it to others and so on

evaporation to affect scales weighing to one-quarter ounce. No. 4 lost

less than No. 1 because, as in the case of the sand, the water could

not climb rapidly to the surface on the coarse crumbs of soil. The

loss that did take place from No. 4 was what the air took from the

loosely stirred soil on the surface with a very little from the lower

soil. Simply stirring the surface of the sod in No. 4 reduced the loss

of water to less than half the loss from the hard soil in No. 1.

This experiment gives us the clew to the method of checking loss of

water from the soil by evaporation. It is to keep the water from

climbing up to the surface, or check the power of the soil to pump the

water to the surface by making it loose on top. This loose soil is

called a soil mulch. Everything that we do to the soil that loosens

and crumbles the surface tends to check the loss of water by

evaporation from the soil below.

[Illustration: FIG. 30.--TO SHOW THE EFFECT OF A SOIL MULCH

1. Packed soil, lost in 7 days 5.5 ozs. water, equal to 75 tons per

acre.

2. Packed soil, covered with straw, lost in 7 days 2 ozs. water, equal

to 27 tons per acre.

3. Packed soil, covered with sand, lost in 7 days 0 ozs. water, equal to

tons per acre.

4. Packed soil, covered with soil mulch, lost in 7 days 2.5 ozs.

water, equal to 34 tons per acre.]

CHAPTER VII

SOIL TEMPERATURE

We learned that roots need heat for their growth and development. Now

what is the relation of the different kinds of soil toward heat or

what are their relative powers to absorb and hold heat?

=Experiment.=–Some days before this experiment, spread on a dry floor

about a half bushel each of sand, clay and decayed leaf mould or black

woods soil. Stir them occasionally till they are thoroughly dry. When

they are dry place them separately in three boxes or large flower pots

and keep dry. In three similar boxes or pots place wet sand, wet clay,

and wet humus. Place a thermometer in each of the soils, placing the

bulb between one and two inches below the surface (Fig. 31). Then

place the soils out of doors where the sun can shine on them and leave

them several days. If a rain should come up protect the dry soils.

Observe and make a record of the temperatures of each soil several

times a day. Chart the average of several days observations. Fig. 32

shows the averages of several days observations on a certain set of

soils.

It will be noticed that the temperature of the soils increased until

the early part of the afternoon and after that time they lost heat.

[Illustration: FIG. 31.--SOIL TEMPERATURE EXPERIMENT.

Thermometer in pot of soil.]

HOW SOILS ARE WARMED

=Experiment.=–Hold your hand in bright sunlight or near a warm stove

or radiator. Your hand is warmed by heat radiated from the sun or warm

stove through the air to your body. In the same manner the rays of the

sun heat the surface of the soil.

=Experiment.=–Take the stove poker or any small iron rod and hold one

end of it in the fire or hold one end of a piece of wire in a candle

or lamp flame. The end of the rod or wire will quickly become very hot

and heat will gradually be carried its entire length until it becomes

too hot to hold. This carrying of the heat from particle to particle

through the length of the rod is called heating by conduction. Now

when the warm rays of the sun reach the soil, or a warm wind blows

over it, the surface particles are warmed and then pass the heat on to

the next ones below, and these in turn pass it to others and so on

till the soil becomes heated to a considerable depth by conduction.

A clay soil will absorb heat by conduction faster than a sandy soil

because the particles of the clay lie so close together that the heat

passes more readily from one to another than in the case of the

coarser sand.

If the soil is open and porous, warm air and warm rains can enter

readily and carry heat to the lower soil.

You have noticed how a pile of stable manure steams in cold weather.

You doubtless know that manure from the horse stable is often used to

furnish heat for hotbeds and for sweet potato beds.

Now the heat which warms the manure and sends the steam out of it, and

warms the hotbed and sweet potato bed, is produced by the decaying or

rotting of the manure. More or less heat is produced by the decay of

all kinds of organic matter. So if the soil is well supplied with

organic matter, the decay of this material will add somewhat to the

warmth of the soil.

HOW SOILS LOSE HEAT

Wet one of your fingers and hold your hand up in the air. The wet

finger will feel colder than the others and will gradually become dry.

This is because some of the heat of your finger is being used to dry

up the water or change it into a vapor, or in other words to evaporate

it.

In the same manner a wet soil loses heat by the evaporation of water

from its surface.

=Experiment.=–Heat an iron rod, take it from the fire and hold it

near your face or hand. You will feel the heat without touching the

rod. The heat is radiated from the rod through the air to your body

and the rod gradually cools. In the same way the soil may lose its

heat by radiating it into the air. A clay soil will lose more heat by

radiation than a sandy soil because the clay is more compact.

CONDITIONS WHICH INFLUENCE SOIL TEMPERATURE

It will be noticed that the dry soils are warmer than the wet ones.

Why is this? Scientists tell us that it takes a great deal more heat

to warm water than it does to warm other substances. Therefore when

soil is wet it takes much more heat to warm it than if it were dry.

It will be seen that of the dry soils the humus is the warmest. Why?

=Experiment.=–Take two thermometers, wrap the bulb of one with a

piece of black or dark colored cloth and the bulb of the other with a

piece of white cloth, then place them where the sun will shine on the

cloth covered bulbs. The mercury in both thermometers will be seen to

rise, but in the thermometer with the dark cloth about the bulb it

will rise faster and higher than in the other. This shows that the

dark cloth absorbs heat faster than the white cloth. In the same

manner a dark soil will absorb heat faster than a light colored soil;

therefore it will be warmer if dry.

Why was the dry clay warmer than the dry sand?

Because its darker color helped it to absorb heat more rapidly than

the sand, and, as the particles were smaller and more compact, heat

was carried into it more rapidly by conduction.

Why were the wet humus and clay cooler than the wet sand?

As they were darker in color and the clay was more compact than the

sand, they must have absorbed more heat, but they also held more

water, and, therefore, lost more heat by evaporation.

[Illustration: FIG. 32.

Charts showing average temperature of a set of dry and wet soils

during a period of five days. _H_, humus; _C_, clay; _S_, sand.]

till the soil becomes heated to a considerable depth by conduction.

A clay soil will absorb heat by conduction faster than a sandy soil

because the particles of the clay lie so close together that the heat

passes more readily from one to another than in the case of the

coarser sand.

If the soil is open and porous, warm air and warm rains can enter

readily and carry heat to the lower soil.

You have noticed how a pile of stable manure steams in cold weather.

You doubtless know that manure from the horse stable is often used to

furnish heat for hotbeds and for sweet potato beds.

Now the heat which warms the manure and sends the steam out of it, and

warms the hotbed and sweet potato bed, is produced by the decaying or

rotting of the manure. More or less heat is produced by the decay of

all kinds of organic matter. So if the soil is well supplied with

organic matter, the decay of this material will add somewhat to the

warmth of the soil.

HOW SOILS LOSE HEAT

Wet one of your fingers and hold your hand up in the air. The wet

finger will feel colder than the others and will gradually become dry.

This is because some of the heat of your finger is being used to dry

up the water or change it into a vapor, or in other words to evaporate

it.

In the same manner a wet soil loses heat by the evaporation of water

from its surface.

=Experiment.=–Heat an iron rod, take it from the fire and hold it

near your face or hand. You will feel the heat without touching the

rod. The heat is radiated from the rod through the air to your body

and the rod gradually cools. In the same way the soil may lose its

heat by radiating it into the air. A clay soil will lose more heat by

radiation than a sandy soil because the clay is more compact.

CONDITIONS WHICH INFLUENCE SOIL TEMPERATURE

It will be noticed that the dry soils are warmer than the wet ones.

Why is this? Scientists tell us that it takes a great deal more heat

to warm water than it does to warm other substances. Therefore when

soil is wet it takes much more heat to warm it than if it were dry.

It will be seen that of the dry soils the humus is the warmest. Why?

=Experiment.=–Take two thermometers, wrap the bulb of one with a

piece of black or dark colored cloth and the bulb of the other with a

piece of white cloth, then place them where the sun will shine on the

cloth covered bulbs. The mercury in both thermometers will be seen to

rise, but in the thermometer with the dark cloth about the bulb it

will rise faster and higher than in the other. This shows that the

dark cloth absorbs heat faster than the white cloth. In the same

manner a dark soil will absorb heat faster than a light colored soil;

therefore it will be warmer if dry.

Why was the dry clay warmer than the dry sand?

Because its darker color helped it to absorb heat more rapidly than

the sand, and, as the particles were smaller and more compact, heat

was carried into it more rapidly by conduction.

Why were the wet humus and clay cooler than the wet sand?

As they were darker in color and the clay was more compact than the

sand, they must have absorbed more heat, but they also held more

water, and, therefore, lost more heat by evaporation.

[Illustration: FIG. 32.

Charts showing average temperature of a set of dry and wet soils

during a period of five days. _H_, humus; _C_, clay; _S_, sand.]

[Illustration: FIG. 33.

To show the value of organic matter. 1 contains clay subsoil; 2, clay

subsoil and fertilizer; 3, clay subsoil and organic matter. All

planted at the same time.]

Of the dry soils, then, the humus averaged warmest, because, on

account of its dark color, it absorbed heat more readily than the

others. The dry clay was warmer than the sand on account of its color

and compact texture. Of the wet soils the sand was the warmest,

because, on account of its holding less moisture, less heat was

required to raise its temperature and there was less cooling by

evaporation, while the other soils, although they absorbed more heat

than the sand, lost more on account of greater evaporation, due to

their holding more moisture. Why are sandy soils called warm soils and

clay soils said to be cold?

How may we check losses of heat from the soil?

If we make a mulch on the surface of the soil evaporation will be

checked and therefore loss of heat by evaporation will be checked

also. The mulch will also check the conduction of heat from the lower

soil to the surface and therefore check loss of heat by radiation from

the surface.

VALUE OF ORGANIC MATTER

Figure 33 illustrates a simple way to show the value of organic matter

in the soil. The boxes are about twelve inches square and ten inches

deep. They were filled with a clay subsoil taken from the second foot

below the surface of the field. To the second box was added sufficient

commercial fertilizer to supply the plants with all necessary plant

food. To the third box was added some peat or decayed leaves, in

amount about ten per cent. of the clay subsoil. The corn was then

planted and the boxes were all given the same care. The better growth

of the corn in the third box was due to the fact that the organic

matter not only furnished food for the corn but during its decay

prepared mineral plant food that was locked up in the clay, and also

brought about better conditions of air and moisture by improving the

texture of the soil. The plants in the second box had sufficient plant

food, but did not make better growth because poor texture prevented

proper conditions of air and moisture. “And that’s another witness”

for organic matter. Decaying organic matter or humus is really the

life of the soil and it is greatly needed in most of the farm soils of

the eastern part of the country. It closes the pores of sandy soils

and opens the clay, thus helping the sand to soak up and hold more

moisture and lessening excessive ventilation, and at the same time

helping the roots to take a firmer hold. It helps the clay to absorb

rain, helps it to pump water faster, helps it to hold water longer in

dry weather, increases ventilation, favors root penetration and

increases heat absorption. We can increase the amount of organic

matter in the soil by plowing in stable manure, leaves and other

organic refuse of the farm, or we can plow under crops of clover,

grass, grain or other crops grown for that purpose.

CHAPTER VIII

PLANT FOOD IN THE SOIL

We learned in previous paragraphs that the roots of plants take food

from the soil, and that a condition necessary for the root to do its

work for the plant was the presence of available plant food in

sufficient quantities.

What is plant food? For answer let us go to the plant and ask it what

it is made of.

=Experiment.=–Take some newly ripened cotton or cotton wadding, a

tree branch, a cornstalk, and some straw or grass. Pull the cotton

apart, then twist some of it and pull apart; in turn break the branch,

[Illustration: FIG. 33.

To show the value of organic matter. 1 contains clay subsoil; 2, clay

subsoil and fertilizer; 3, clay subsoil and organic matter. All

planted at the same time.]

Of the dry soils, then, the humus averaged warmest, because, on

account of its dark color, it absorbed heat more readily than the

others. The dry clay was warmer than the sand on account of its color

and compact texture. Of the wet soils the sand was the warmest,

because, on account of its holding less moisture, less heat was

required to raise its temperature and there was less cooling by

evaporation, while the other soils, although they absorbed more heat

than the sand, lost more on account of greater evaporation, due to

their holding more moisture. Why are sandy soils called warm soils and

clay soils said to be cold?

How may we check losses of heat from the soil?

If we make a mulch on the surface of the soil evaporation will be

checked and therefore loss of heat by evaporation will be checked

also. The mulch will also check the conduction of heat from the lower

soil to the surface and therefore check loss of heat by radiation from

the surface.

VALUE OF ORGANIC MATTER

Figure 33 illustrates a simple way to show the value of organic matter

in the soil. The boxes are about twelve inches square and ten inches

deep. They were filled with a clay subsoil taken from the second foot

below the surface of the field. To the second box was added sufficient

commercial fertilizer to supply the plants with all necessary plant

food. To the third box was added some peat or decayed leaves, in

amount about ten per cent. of the clay subsoil. The corn was then

planted and the boxes were all given the same care. The better growth

of the corn in the third box was due to the fact that the organic

matter not only furnished food for the corn but during its decay

prepared mineral plant food that was locked up in the clay, and also

brought about better conditions of air and moisture by improving the

texture of the soil. The plants in the second box had sufficient plant

food, but did not make better growth because poor texture prevented

proper conditions of air and moisture. “And that’s another witness”

for organic matter. Decaying organic matter or humus is really the

life of the soil and it is greatly needed in most of the farm soils of

the eastern part of the country. It closes the pores of sandy soils

and opens the clay, thus helping the sand to soak up and hold more

moisture and lessening excessive ventilation, and at the same time

helping the roots to take a firmer hold. It helps the clay to absorb

rain, helps it to pump water faster, helps it to hold water longer in

dry weather, increases ventilation, favors root penetration and

increases heat absorption. We can increase the amount of organic

matter in the soil by plowing in stable manure, leaves and other

organic refuse of the farm, or we can plow under crops of clover,

grass, grain or other crops grown for that purpose.

CHAPTER VIII

PLANT FOOD IN THE SOIL

We learned in previous paragraphs that the roots of plants take food

from the soil, and that a condition necessary for the root to do its

work for the plant was the presence of available plant food in

sufficient quantities.

What is plant food? For answer let us go to the plant and ask it what

it is made of.

=Experiment.=–Take some newly ripened cotton or cotton wadding, a

tree branch, a cornstalk, and some straw or grass. Pull the cotton

apart, then twist some of it and pull apart; in turn break the branch,

the cornstalk and the straw. The cotton does not pull apart readily

nor do the others break easily; this is because they all contain long,

tough fibres. These fibres are called woody fibre or cellulose. The

cotton fibre is nearly pure cellulose.

=Experiment.=–Get together some slices of white potato, sweet potato,

parsnip, broken kernels of corn, wheat and oats, a piece of laundry

starch and some tincture of iodine diluted to about the color of weak

tea. Rub a few drops of the iodine on the cut surfaces of the

potatoes, parsnip, and the broken surfaces of the grains. Notice that

it turns them purple. Now drop a drop of the iodine on the laundry

starch. It turns that purple also. This experiment tells us that

plants contain starch.

=Experiment.=–Chew a piece of sorghum cane, sugar cane, cornstalk,

beet root, turnip root, apple or cabbage. They all taste sweet and

must therefore contain sugar.

Examine a number of peach and cherry trees. You will find on the trunk

and branches more or less of a sticky substance called gum.

=Experiment.=–Crush on paper seeds of cotton, castor-oil bean,

peanuts, Brazil nuts, hickory nuts, butternuts, etc. They make grease

spots; they contain fat and oil.

=Experiment.=–Chew whole grains of wheat and find a gummy

mucilaginous substance called wheat gum, or wet a pint of wheat flour

to a stiff dough, let it stand about an hour, and then wash the starch

out of it by kneading it under a stream of running water or in a pan

of water, changing the water frequently. The result will be a tough,

yellowish gray, elastic mass called gluten. This is the same as the

wheat gum and is called an albuminoid because it contains nitrogen and

is like albumen, a substance like the white of an egg.

If we crush or grate some potatoes or cabbage leaves to a pulp and

separate the juice, then heat the clear juice, a substance will

separate in a flaky form and settle to the bottom of the liquid. This

is vegetable albumen.

[Illustration: FIG. 34.

Soy-bean roots. Showing nodules of tubercles, the homes of

nitrogen-fixing bacteria.]

[Illustration: FIG. 35.

Garden-pea roots, showing tubercles or nodules, the homes of

nitrogen-fixing bacteria.]

=Experiment.=–Crush the leaves or stems of several growing plants and

notice that the crushed and exposed parts are moist. In a potato or an

apple we find a great deal of moisture. Plants then are partly made of

water. In fact growing plants are from 65 to 95 per cent. water.

=Experiment.=–Expose a plant or part of a plant to heat; the water is

driven off and there remains a dry portion. Heat the dry part to a

high degree and it burns; part passes into the air as smoke and part

remains behind as ashes.

We have found then the following substances in plants: Woody fibre or

cellulose, starch, sugar, gum, fats and oils, albuminoids, water,

ashes. Aside from these are found certain coloring matters, certain

acids and other matters which give taste, flavor, and poisonous

qualities to fruits and vegetables. More or less of all these

substances are found in all plants. Now these are all compound

substances. That is, they can all be broken down into simpler

substances, and with the exception of the water and the ashes, the

plants do not take them directly from the soil.

The chemists tell us that these substances are composed of certain

chemical elements, some of which the plant obtains from the air, some

from the soil and some from water.

The following table gives the substances found in plants, the elements

of which they are composed, and the sources from which the plants

obtain them:

the cornstalk and the straw. The cotton does not pull apart readily

nor do the others break easily; this is because they all contain long,

tough fibres. These fibres are called woody fibre or cellulose. The

cotton fibre is nearly pure cellulose.

=Experiment.=–Get together some slices of white potato, sweet potato,

parsnip, broken kernels of corn, wheat and oats, a piece of laundry

starch and some tincture of iodine diluted to about the color of weak

tea. Rub a few drops of the iodine on the cut surfaces of the

potatoes, parsnip, and the broken surfaces of the grains. Notice that

it turns them purple. Now drop a drop of the iodine on the laundry

starch. It turns that purple also. This experiment tells us that

plants contain starch.

=Experiment.=–Chew a piece of sorghum cane, sugar cane, cornstalk,

beet root, turnip root, apple or cabbage. They all taste sweet and

must therefore contain sugar.

Examine a number of peach and cherry trees. You will find on the trunk

and branches more or less of a sticky substance called gum.

=Experiment.=–Crush on paper seeds of cotton, castor-oil bean,

peanuts, Brazil nuts, hickory nuts, butternuts, etc. They make grease

spots; they contain fat and oil.

=Experiment.=–Chew whole grains of wheat and find a gummy

mucilaginous substance called wheat gum, or wet a pint of wheat flour

to a stiff dough, let it stand about an hour, and then wash the starch

out of it by kneading it under a stream of running water or in a pan

of water, changing the water frequently. The result will be a tough,

yellowish gray, elastic mass called gluten. This is the same as the

wheat gum and is called an albuminoid because it contains nitrogen and

is like albumen, a substance like the white of an egg.

If we crush or grate some potatoes or cabbage leaves to a pulp and

separate the juice, then heat the clear juice, a substance will

separate in a flaky form and settle to the bottom of the liquid. This

is vegetable albumen.

[Illustration: FIG. 34.

Soy-bean roots. Showing nodules of tubercles, the homes of

nitrogen-fixing bacteria.]

[Illustration: FIG. 35.

Garden-pea roots, showing tubercles or nodules, the homes of

nitrogen-fixing bacteria.]

=Experiment.=–Crush the leaves or stems of several growing plants and

notice that the crushed and exposed parts are moist. In a potato or an

apple we find a great deal of moisture. Plants then are partly made of

water. In fact growing plants are from 65 to 95 per cent. water.

=Experiment.=–Expose a plant or part of a plant to heat; the water is

driven off and there remains a dry portion. Heat the dry part to a

high degree and it burns; part passes into the air as smoke and part

remains behind as ashes.

We have found then the following substances in plants: Woody fibre or

cellulose, starch, sugar, gum, fats and oils, albuminoids, water,

ashes. Aside from these are found certain coloring matters, certain

acids and other matters which give taste, flavor, and poisonous

qualities to fruits and vegetables. More or less of all these

substances are found in all plants. Now these are all compound

substances. That is, they can all be broken down into simpler

substances, and with the exception of the water and the ashes, the

plants do not take them directly from the soil.

The chemists tell us that these substances are composed of certain

chemical elements, some of which the plant obtains from the air, some

from the soil and some from water.

The following table gives the substances found in plants, the elements

of which they are composed, and the sources from which the plants

obtain them:

———————————————————-+

Substances found | Elements of which | Sources from |

in plants. | they are made. | which plants |

| | obtain them. |

——————-+———————+—————-+

Cellulose or | | |

woody fibre | Carbon | Air |

Starch |———————+—————-+

Sugar | | |

Gum | Oxygen | Water |

Fat and Oil | Hydrogen | |

——————-+———————+—————-+

| Carbon | Air |

+———————+—————-+

Albuminoids | Oxygen | Water |

| Hydrogen | |

+———————+—————-+

| _Nitrogen_ | |

| Sulphur | |

| Phosphorus | |

——————-+———————| Soil +

| _Phosphorus_ | |

| _Potassium_ | |

Ashes | _Calcium_ | |

| Magnesium | |

| Iron | |

——————-+———————+—————-+

Water | Oxygen | Soil |

| Hydrogen | |

—————————————–+—————-+

Here is a brief description of these chemical elements.

Oxygen, a colorless gas, forms one-fifth of the air.

Hydrogen, a colorless gas, forms a part of water.

Carbon, a dark solid, forms nearly one-half of all organic matter;

charcoal is one of its forms. The lead in your pencil is another

example.

Nitrogen, a colorless gas, forms four-fifths of the air. Found in all

albuminoids.

Sulphur, a yellow solid.

Phosphorus, a yellowish white solid.

Potassium, a silver white solid.

Calcium, a yellowish solid. Found in limestone.

Magnesium, a silver white solid.

Iron, a silver gray solid.

Of these elements the nitrogen, sulphur, phosphorus, potassium,

calcium, magnesium, and iron must not only exist in the soil but must

also be there in such form that the plant can use them. The plant does

not use them in their simple elementary form but in various compounds.

These compounds must be soluble in water or in weak acids.

Of these seven elements of plant food the nitrogen, phosphorus, and

potassium and calcium are of particular importance to the farmer,

because they do not always exist in the soil in sufficient available

quantities to produce profitable crops. Professor Roberts, of Cornell

University, tells us that an average acre of soil eight inches deep

contains three thousand pounds of nitrogen. The nitrogen exists

largely in the humus of the soil and it is only as the humus decays

that the nitrogen is made available. Here is another reason for

keeping the soil well supplied with organic matter. The decay of this

organic matter is hastened by working the soil; therefore good tillage

helps to supply the plant with nitrogen.

If the nitrogen becomes available when there is no crop on the soil it

———————————————————-+

Substances found | Elements of which | Sources from |

in plants. | they are made. | which plants |

| | obtain them. |

——————-+———————+—————-+

Cellulose or | | |

woody fibre | Carbon | Air |

Starch |———————+—————-+

Sugar | | |

Gum | Oxygen | Water |

Fat and Oil | Hydrogen | |

——————-+———————+—————-+

| Carbon | Air |

+———————+—————-+

Albuminoids | Oxygen | Water |

| Hydrogen | |

+———————+—————-+

| _Nitrogen_ | |

| Sulphur | |

| Phosphorus | |

——————-+———————| Soil +

| _Phosphorus_ | |

| _Potassium_ | |

Ashes | _Calcium_ | |

| Magnesium | |

| Iron | |

——————-+———————+—————-+

Water | Oxygen | Soil |

| Hydrogen | |

—————————————–+—————-+

Here is a brief description of these chemical elements.

Oxygen, a colorless gas, forms one-fifth of the air.

Hydrogen, a colorless gas, forms a part of water.

Carbon, a dark solid, forms nearly one-half of all organic matter;

charcoal is one of its forms. The lead in your pencil is another

example.

Nitrogen, a colorless gas, forms four-fifths of the air. Found in all

albuminoids.

Sulphur, a yellow solid.

Phosphorus, a yellowish white solid.

Potassium, a silver white solid.

Calcium, a yellowish solid. Found in limestone.

Magnesium, a silver white solid.

Iron, a silver gray solid.

Of these elements the nitrogen, sulphur, phosphorus, potassium,

calcium, magnesium, and iron must not only exist in the soil but must

also be there in such form that the plant can use them. The plant does

not use them in their simple elementary form but in various compounds.

These compounds must be soluble in water or in weak acids.

Of these seven elements of plant food the nitrogen, phosphorus, and

potassium and calcium are of particular importance to the farmer,

because they do not always exist in the soil in sufficient available

quantities to produce profitable crops. Professor Roberts, of Cornell

University, tells us that an average acre of soil eight inches deep

contains three thousand pounds of nitrogen. The nitrogen exists

largely in the humus of the soil and it is only as the humus decays

that the nitrogen is made available. Here is another reason for

keeping the soil well supplied with organic matter. The decay of this

organic matter is hastened by working the soil; therefore good tillage

helps to supply the plant with nitrogen.

If the nitrogen becomes available when there is no crop on the soil it

will be washed out by rains and so lost. Therefore the soil,

especially if it is sandy, should be covered with a crop the year

through. Many lands lose large amounts of plant food by being left

bare through the fall and winter, especially in those parts of the

country where the land does not freeze. The phosphorus, potassium and

calcium also exist in most soils in considerable quantities, but often

are not available; thorough tillage and the addition of organic matter

will help to make them available, and new supplies may be added in the

form of fertilizers. Calcium is found in nearly all soils in

sufficient quantities for most crops, but sometimes there is not

enough of it for such crops as clover, cowpea, alfalfa, etc. It is

also used to improve soil texture. The entire subject of commercial

fertilizers is based almost entirely on the fact of the lack of these

four elements in the soil in sufficient available quantities to grow

profitable crops. The plant gets its phosphorus from phosphoric acid,

its potassium from potash, and its calcium from lime.

There is a class of plants which have the power of taking free

nitrogen from the air. These are the leguminous plants; such as

clover, beans, cowpeas, alfalfa, soy bean, etc. They do it through the

acid of microscopic organisms called bacteria which live in nodules or

tubercles on the roots of these plants (Figs. 34-35). Collect roots of

these plants and find the nodules on them. The bacteria take nitrogen

from the air which penetrates the soil and give it over to the plants.

Here is another reason for good soil ventilation.

This last fact brings us to another very important property of soils.

Soils have existing in them many very small plants called bacteria.

They are so very small that it would take several hundred of them to

reach across the edge of this sheet of paper. We cannot see them with

the naked eye but only with the most powerful microscopes. Some of

these minute plants are great friends to the farmer, for it is largely

through their work that food is made available for the higher plants.

Some of them break down the organic matter and help prepare the

nitrogen for the larger plants. Others help the leguminous plants to

feed on the nitrogen of the air. To do their work they need warmth,

moisture, air, and some mineral food; these conditions we bring about

by improving the texture of the soil by means of thorough tillage and

the use of organic matter.

CHAPTER IX

SEEDS

CONDITIONS NECESSARY FOR SEEDS TO SPROUT

In the spring comes the great seed-planting time on the farm, in the

home garden and in the school garden. Many times the questions will be

asked: Why didn’t those seeds come up? How shall I plant seeds so as

to help them sprout easily and grow into strong plants? To answer

these questions, perform a few experiments with seeds, and thus find

out what conditions are necessary for seeds to sprout, or germinate.

For these experiments you will need a few teacups, glass tumblers or

tin cans, such as tomato cans or baking-powder cans; a few plates,

either of tin or crockery; some wide-mouth bottles that will hold

about half a pint, such as pickle, olive, or yeast bottles or

druggists’ wide-mouth prescription bottles; and a few pieces of cloth.

Also seeds of corn, garden peas and beans.

=Experiment.=–Put seeds of corn, garden peas, and beans (about a

handful of each) to soak in bottles or tumblers of water. Next day,

two hours earlier in the day, put a duplicate lot of seeds to soak.

When this second lot of seeds has soaked two hours, you will have two

lots of soaked seeds of each kind, one of which has soaked twenty-four

hours and the other two hours. Now take these seeds from the water and

dry the surplus water from them by gently patting or rubbing a few at

a time in the folds of a piece of cloth, taking care not to break the

skin or outer coating of the seed. Place them in dry bottles, putting

in enough to cover the bottoms of the bottles about three seeds deep;

cork the bottles. If you cannot find corks, tie paper over the mouths

of the bottles. Label the bottles “Seeds soaked 24 hours,” “Seeds

will be washed out by rains and so lost. Therefore the soil,

especially if it is sandy, should be covered with a crop the year

through. Many lands lose large amounts of plant food by being left

bare through the fall and winter, especially in those parts of the

country where the land does not freeze. The phosphorus, potassium and

calcium also exist in most soils in considerable quantities, but often

are not available; thorough tillage and the addition of organic matter

will help to make them available, and new supplies may be added in the

form of fertilizers. Calcium is found in nearly all soils in

sufficient quantities for most crops, but sometimes there is not

enough of it for such crops as clover, cowpea, alfalfa, etc. It is

also used to improve soil texture. The entire subject of commercial

fertilizers is based almost entirely on the fact of the lack of these

four elements in the soil in sufficient available quantities to grow

profitable crops. The plant gets its phosphorus from phosphoric acid,

its potassium from potash, and its calcium from lime.

There is a class of plants which have the power of taking free

nitrogen from the air. These are the leguminous plants; such as

clover, beans, cowpeas, alfalfa, soy bean, etc. They do it through the

acid of microscopic organisms called bacteria which live in nodules or

tubercles on the roots of these plants (Figs. 34-35). Collect roots of

these plants and find the nodules on them. The bacteria take nitrogen

from the air which penetrates the soil and give it over to the plants.

Here is another reason for good soil ventilation.

This last fact brings us to another very important property of soils.

Soils have existing in them many very small plants called bacteria.

They are so very small that it would take several hundred of them to

reach across the edge of this sheet of paper. We cannot see them with

the naked eye but only with the most powerful microscopes. Some of

these minute plants are great friends to the farmer, for it is largely

through their work that food is made available for the higher plants.

Some of them break down the organic matter and help prepare the

nitrogen for the larger plants. Others help the leguminous plants to

feed on the nitrogen of the air. To do their work they need warmth,

moisture, air, and some mineral food; these conditions we bring about

by improving the texture of the soil by means of thorough tillage and

the use of organic matter.

CHAPTER IX

SEEDS

CONDITIONS NECESSARY FOR SEEDS TO SPROUT

In the spring comes the great seed-planting time on the farm, in the

home garden and in the school garden. Many times the questions will be

asked: Why didn’t those seeds come up? How shall I plant seeds so as

to help them sprout easily and grow into strong plants? To answer

these questions, perform a few experiments with seeds, and thus find

out what conditions are necessary for seeds to sprout, or germinate.

For these experiments you will need a few teacups, glass tumblers or

tin cans, such as tomato cans or baking-powder cans; a few plates,

either of tin or crockery; some wide-mouth bottles that will hold

about half a pint, such as pickle, olive, or yeast bottles or

druggists’ wide-mouth prescription bottles; and a few pieces of cloth.

Also seeds of corn, garden peas and beans.

=Experiment.=–Put seeds of corn, garden peas, and beans (about a

handful of each) to soak in bottles or tumblers of water. Next day,

two hours earlier in the day, put a duplicate lot of seeds to soak.

When this second lot of seeds has soaked two hours, you will have two

lots of soaked seeds of each kind, one of which has soaked twenty-four

hours and the other two hours. Now take these seeds from the water and

dry the surplus water from them by gently patting or rubbing a few at

a time in the folds of a piece of cloth, taking care not to break the

skin or outer coating of the seed. Place them in dry bottles, putting

in enough to cover the bottoms of the bottles about three seeds deep;

cork the bottles. If you cannot find corks, tie paper over the mouths

of the bottles. Label the bottles “Seeds soaked 24 hours,” “Seeds

soaked 2 hours,” and let them stand in a warm place several days. If

there is danger of freezing at night, the bottles of seeds may be kept

in the kitchen or living room where it is warm, until they sprout.

Observe the seeds from day to day. The seeds that soaked twenty-four

hours will sprout readily (Fig. 36), while most, if not all, of those

that soaked only two hours will not sprout. Why is this? It is because

the two-hour soaked seeds do not receive sufficient moisture to carry

on the process of sprouting.

Our experiment teaches us that seeds will not sprout until they

receive enough moisture to soak them through and through.

This also teaches that when we plant seeds we must so prepare the soil

for them and so plant them that they will be able to get sufficient

moisture to sprout.

=Experiment.=–Soak some beans, peas or corn, twenty-four hours;

carefully dry them with a cloth. In one half-pint bottle place enough

of them to cover the bottom of the bottle two or three seeds deep;

mark this bottle A. Fill another bottle two-thirds full of them and

mark the bottle B (Fig. 37). Cork the bottles and let them stand for

several days. Also let some seeds remain soaking in the water. The few

seeds in bottle A will sprout, while, the larger number in bottle B

will not sprout, or will produce only very short sprouts. Why do not

the seeds sprout easily in the bottle which is more than half full?

To answer this question try the following experiment:

=Experiment.=–Carefully loosen the cork in bottle B (the bottle

containing poorly sprouted seeds), light a match, remove the cork from

the bottle and introduce the lighted match. The match will stop

burning as soon as it is held in the bottle, because there is no fresh

air in the bottle to keep the match burning. Test bottle A in the same

way. What has become of the fresh air that was in the bottles when the

seeds were put in them? The seeds have taken something from it and

have left bad air in its place; they need fresh air to help them

sprout, but they have not sprouted so well in bottle B because there

was not fresh air enough for so many seeds. The seeds in the water do

not sprout because there is not enough air in the water. Now try

another experiment.

[Illustration: FIG. 36.

To show that seeds need water for germination. The beans in bottle _A_

were soaked 2 hours, those in bottle _B_ were soaked 24 hours. They

were then removed from the water and put into dry bottles.]

[Illustration: FIG. 37.

To show that seeds need air for germination. The beans in both bottles

were soaked 24 hours, and then were put into dry bottles Bottle _A_

contained sufficient air to start the few seeds. Bottle _B_ had not

enough. The water in the tumbler _C_ did not contain sufficient air

for germination. See experiment, page 72.]

[Illustration: FIG. 38.

To show that seeds need air for germination. Corn planted in puddled

clay in tumbler _A_ could not get sufficent air for sprouting. The

moist sand in tumbler _B_ admitted sufficient air for germination.]

=Experiment.=–Fill some tumblers or teacups or tin cans with wet sand

and others with clay that has been wet and then thoroughly stirred

till it is about the consistency of cake batter or fresh mixed mortar.

Take a tumbler of the wet sand and one of the wet clay and plant two

or three kernels of corn in each, pressing the kernels down one-half

or three-quarters of an inch below the surface; cover the seeds and

carefully smooth the surface. In other tumblers plant peas, beans, and

other seeds. Cover the tumblers with saucers, or pieces of glass or

board to keep the soil from drying. Watch them for several days. If

the clay tends to dry and crack, moisten it, fill the cracks and

smooth the surface. The seeds in the sand will sprout but those in the

clay will not (see Fig. 38). Why is this? Water fills the small spaces

between the particles of clay and shuts out the fresh air which is

necessary for the sprouting of the seeds.

This teaches us that when we plant seeds we must so prepare the soil,

soaked 2 hours,” and let them stand in a warm place several days. If

there is danger of freezing at night, the bottles of seeds may be kept

in the kitchen or living room where it is warm, until they sprout.

Observe the seeds from day to day. The seeds that soaked twenty-four

hours will sprout readily (Fig. 36), while most, if not all, of those

that soaked only two hours will not sprout. Why is this? It is because

the two-hour soaked seeds do not receive sufficient moisture to carry

on the process of sprouting.

Our experiment teaches us that seeds will not sprout until they

receive enough moisture to soak them through and through.

This also teaches that when we plant seeds we must so prepare the soil

for them and so plant them that they will be able to get sufficient

moisture to sprout.

=Experiment.=–Soak some beans, peas or corn, twenty-four hours;

carefully dry them with a cloth. In one half-pint bottle place enough

of them to cover the bottom of the bottle two or three seeds deep;

mark this bottle A. Fill another bottle two-thirds full of them and

mark the bottle B (Fig. 37). Cork the bottles and let them stand for

several days. Also let some seeds remain soaking in the water. The few

seeds in bottle A will sprout, while, the larger number in bottle B

will not sprout, or will produce only very short sprouts. Why do not

the seeds sprout easily in the bottle which is more than half full?

To answer this question try the following experiment:

=Experiment.=–Carefully loosen the cork in bottle B (the bottle

containing poorly sprouted seeds), light a match, remove the cork from

the bottle and introduce the lighted match. The match will stop

burning as soon as it is held in the bottle, because there is no fresh

air in the bottle to keep the match burning. Test bottle A in the same

way. What has become of the fresh air that was in the bottles when the

seeds were put in them? The seeds have taken something from it and

have left bad air in its place; they need fresh air to help them

sprout, but they have not sprouted so well in bottle B because there

was not fresh air enough for so many seeds. The seeds in the water do

not sprout because there is not enough air in the water. Now try

another experiment.

[Illustration: FIG. 36.

To show that seeds need water for germination. The beans in bottle _A_

were soaked 2 hours, those in bottle _B_ were soaked 24 hours. They

were then removed from the water and put into dry bottles.]

[Illustration: FIG. 37.

To show that seeds need air for germination. The beans in both bottles

were soaked 24 hours, and then were put into dry bottles Bottle _A_

contained sufficient air to start the few seeds. Bottle _B_ had not

enough. The water in the tumbler _C_ did not contain sufficient air

for germination. See experiment, page 72.]

[Illustration: FIG. 38.

To show that seeds need air for germination. Corn planted in puddled

clay in tumbler _A_ could not get sufficent air for sprouting. The

moist sand in tumbler _B_ admitted sufficient air for germination.]

=Experiment.=–Fill some tumblers or teacups or tin cans with wet sand

and others with clay that has been wet and then thoroughly stirred

till it is about the consistency of cake batter or fresh mixed mortar.

Take a tumbler of the wet sand and one of the wet clay and plant two

or three kernels of corn in each, pressing the kernels down one-half

or three-quarters of an inch below the surface; cover the seeds and

carefully smooth the surface. In other tumblers plant peas, beans, and

other seeds. Cover the tumblers with saucers, or pieces of glass or

board to keep the soil from drying. Watch them for several days. If

the clay tends to dry and crack, moisten it, fill the cracks and

smooth the surface. The seeds in the sand will sprout but those in the

clay will not (see Fig. 38). Why is this? Water fills the small spaces

between the particles of clay and shuts out the fresh air which is

necessary for the sprouting of the seeds.

This teaches us that when we plant seeds we must so prepare the soil,

and so plant the seeds that they will get enough fresh air to enable

them to sprout, or, in other words, the soil must be well ventilated.

=Experiment.=–Plant seeds of corn and beans in each of two tumblers;

set one out of doors in a cold place and keep the other in a warm

place in the house. The seeds kept in the house will sprout quickly

but those outside in the cold will not sprout at all. This shows us

that seeds will not sprout without heat.

If the weather is warm place one of the tumblers in a refrigerator.

Why don’t we plant corn in December?

Why not plant melons in January?

Why not plant cotton in November?

The seeds of farm crops may be divided into two classes according to

the temperatures at which they will germinate or sprout readily and

can be safely planted.

Class A. Those seeds that will germinate or sprout at an average

temperature of forty-five degrees in the shade, or at about the time

the peach and plum trees blossom:

Barley Beet Parsley

Oats Carrot Parsnip

Rye Cabbage Onion

Wheat Cauliflower Pea

Red Clover Endive Radish

Crimson Clover Kale Turnip

Grasses Lettuce Spinach

These can be planted with safety in the spring as soon as the ground

can be prepared, and some of them, if planted in the fall, live

through the winter.

Class B. Those seeds that will germinate or sprout at an average

temperature of sixty degrees in the shade, or when the apple trees

blossom:

Alfalfa Soy Bean Squash

Cow Pea Pole Bean Cucumber

Corn String Bean Pumpkin

Cotton Melon Tomato

Egg Plant Okra Pepper

We are now ready to answer the question: What conditions are necessary

for seeds to sprout or germinate? These conditions are:

The presence of enough moisture to keep the seed thoroughly soaked.

The presence of fresh air.

The presence of more or less heat.

This teaches us that when we plant seeds in the window box or in the

garden or on the farm we must so prepare the soil and so plant the

seeds that they will be able to obtain sufficient moisture, heat, and

air for sprouting. The moisture must be film water, for if it is free

water or capillary water filling the soil pores, there can be no

ventilation and, therefore, no sprouting.

SEED TESTING

In a previous experiment (page 73) the seeds planted in the wet clay

did not sprout (see Fig. 38). In answer to the question, “Why is

this?” some will say the seeds were bad. It often happens on the farm

that the seeds do not sprout well and the farmer accuses the seedsman

of selling him poor seed, but does not think that he himself may be

the cause of the failure by not putting the seeds under the proper

conditions for sprouting. How can we tell whether or not our seeds

will sprout if properly planted? We can test them by putting a number

of seeds from each package under proper conditions of moisture, heat