Principles of farm practice

Preface

For several years the author has been giving a survey course in agriculture for teachers and prospective teachers attending the summer session of Miami University. Many of these students, who were teachers of agriculture, have expressed a wish that the contents of the course be assembled and organized into a textbook adapted for use in the problem method of instruction.

An attempt was made to organize the material of this course around the farm as the unifying center. It was then submitted to trial in both regular and Smith-Hughes courses in high schools. The results of this test seemed to justify making the material thus organized available for instruction in the form presented in this book.

The author spent some time visiting high schools of Massachusetts where agriculture was being taught by the project method. Through the courtesy of Dr. Rufus W. Stimson, Director of the Massachusetts Agricultural Education Service, the author was able to see many of the projects in actual operation and to study the plans from which they were developed.

He also visited the agricultural colleges of many of the great farming states to inspect the work of training teachers for agricultural instruction. At this time he came into contact with a number of men interested in problems of agricultural education and with specialists in various scientific aspects of agriculture.

Mention is made of this fact in acknowledgement to those men for their contribution, though made unconsciously, to the preparation of this book. The field of agriculture is too large for one person always to be sure of his ground even in an elementary textbook. For this reason the author feels greatly indebted to iv PREFACE

those who have helped give authority to much that appears in the following pages.

Particular reference should be made to Mrs. Mildred Douthitt Hiers, Mr. Charles Stephenson, and Mr. Clyde Hissong for advice and suggestions as to arrangement of subject matter from the teaching standpoint, and to Mr. Hissong, especially, for trying out the material thus arranged in a Smith-Hughes high school; to Miss Miss Grace Kiernan for compiling index and reading proof; to Professor John V. Ankeney, of the University of Missouri, for reading the manuscript and for several illustrations; to Professor Bruce Fink, of Miami University, for critical reading of Chapters I, XIV and XV; to Professor T. L. Harris, of the University of West Virginia, for suggestions in preparation of Chapters XXVIII, XIX and XXX; to Dean Alfred Vivian, of the Agricultural College of Ohio State University, for comments on correct theories and practices relating to soil fertility and use of fertiUzers; to Professor G. I. Christie, Director of the Agricultural Experiment Station, Purdue University, and to members of the staff, for many helpful suggestions and for reading the proof of the entire book; to Mrs. Emma Johnson Davis, wife of the author, for her great help in preparing the manuscript for publication and in reading the proof sheets.

Acknowledgement is given in the description of the figures as they appear in the text for those not made by the author or under his direction.

EDITOR'S INTRODUCTION

Principles of Farm Practice is written with the fundamental fact in mind that Agriculture teaching, like agricultural life, must be lived from day to day. Instruction in theory and the accumulation of facts are of little value in themselves. The textbook and teaching process that make the things taught part of the student's life, because of logical arrangement and practical apphcation to every day affairs, are alone worth while. Such it is hoped, the present book will prove to be.

In teaching such a primary subject as agriculture, it is well to keep in mind that food, clothing and shelter come first in the list of human wants. Until they are provided the people, either savage or civihzed, will pay httle attention to the other desirable things of life. If modern agricultural people, therefore, ^re to live well rounded lives they must first of all be put in a position to make a good living out of the land. In the United States about seventy-five percent of the nation's wealth comes immediately out of the land in one form or another. The farmers are the greatest wealth producers we have, although not the greatest wealth keepers; for, under the present system of agricultural organization the farmers are able to keep only a small part of this wealth for themselves. The schools must, accordingly, teach new things, not alone .in agricultural production — acre by acre, but also in how to prepare products for market and how to market them.

This book accordingly aims to help the children to become better and more scientific farm folk than those who have gone before them; but most of all it aims to help them to live happy, contented lives in the open country, in fullest harmony with the nature environment round about them. It is not enough to instruct in agricultural objects and practices; the educational and spiritual views of agricultural hfe are fully as essential. All of these are given careful consideration in the book.

Contents

CHAPTER PAGE

I. What We Need to Know about Plants to Help

Them Grow i

Chapter I What We Need To Know About Plants To Help Them Grow

Plants, the basis of agriculture. — Plants are the foundation of all agriculture either directly when they supply food, clothing, or some other human need, or indirectly when they furnish feed for domestic animals. Since plants are really the basis of agricultural production, we must, first of all, in a study of agriculture consider some of the main facts about how plants live.

Plants are living beings. — That plants have life is a fact that needs to be repeated though it may be known to all who read these lines. It seems necessary to emphasize this because we habitually think of the word '' living " as meaning to move around and behave like animals. As a matter of fact, plants are as much alive as animals. In order to live, they require essentially the same things as animals do; but they get these things in an entirely different way. The most important of these requirements are food, water, and air.

How plants get food. — The green plants make their own food from raw materials obtained from air, soil, and water. The basic food material made by the plant is starch or a starch-like substance. Starch is composed of three elements: carbon, oxygen, and hydrogen. The carbon and oxygen come from a compound always present in the air, known as carbon dioxide, and the hydrogen from water. The starch-making process goes on in the green part of the plant, mostly in the leaves. But the work of starch-making from carbon dioxide and water requires power, or energy. This power comes from sunHght. Here we have an explanation of the fact that green plants thrive only in the presence of sunlight.

With starch-like substances thus formed as a basis, other food materials are made. For example, an important food known as protein is formed by using the elements composing the starch-like compounds made by the leaves, and nitrogen which is brought to the plant in substances dissolved in soil water. Besides nitrogen, a number of other chemical elements obtained from materials dissolved in soil water seem to be necessary for food-making in the plant. The most important of these, from an agricultural standpoint, are phosphorus and potassium.

Why plants need water. — That plants need water is shown by the fact that they soon die when deprived of water. A leading authority on plant life says that the greatest thing influencing plant growth is water. It is used by the plant in several ways. Its part in supplying the raw material for starch-making and in bringing to the plant several elements from the soil, as nitrogen, phosphorus, and potassium, has been mentioned. In addition, water helps to make the plant rigid; it composes most of the sap, transfers food materials from place to place in the plant, and assists in the control of temperature.

Water passes through healthy, vigorous plants in a con-, stant stream, entering through the roots and escaping in the form of watery vapor through the leaves. A large amount of water is thus used by a plant during the growing season. It

HELPING PLANTS GROW 3

is estimated that for every pound of dry matter produced by common cultivated crops an average of about 300 pounds of water must pass through the plants. It has been found that a

Diagram of a plant showing its relations to the soil, air, and water.

corn plant may lose nine pounds of water in eight and one-half hours. At this rate an acre of corn would lose fortyeight tons of water — an amount equivalent to one-half inch rainfall in the given time.

How plants get water. — If the roots of a young radish plant which has been developed by placing seed between two moist pieces of paper are examined, they will be found to be covered with fine hairs. These hairs are called root-hairs. They are the absorbing organs of the roots. The roots themselves absorb little water.

They serve to hold the plant in place. They also furnish surface for the development and distribution of root-hairs, in much the same way that twigs and branches of a tree afford surface for the development and distribution of the leaves. All the roots of a plant taken together are known as a root-system. As roots grow in length new root-hairs appear near the root-ends, while the root-hairs farthest away from the ends shrivel up and disappear. Thousands of little roots of a vigorously growing plant push their way into all parts of the upper layers of the soil, where they develop root-hairs for the absorption of water. In this way, much of the capillary water in the region of root growth is reached and supplied to the plant.

The extent of the root-system of a plant can be realized only by carefully measuring or estimating the total length of all the roots. It has been estimated that if all the roots of a nearly mature corn plant were placed end to end they would extend about one thousand feet, and that those of certain

Diagram ot root-hair much enlarged.

A . Cell or root from which root-hair is an outgrowth.

B. Root-hair.

C. Soil particle.

D. Film of water around soil particle.

Arrows show path of water through root-hair.

HELPING PLANTS GROW squash plants would extend fifteen miles. The tendency of a root-system to reach into all parts of the soil near its surface is an important fact to remember. Thus, when the soil between rows of plants, like corn, is cultivated deeply, especially late in the growing season, many feet of small roots will be destroyed.

Root-systems are of two kinds; those having a central root with smaller roots radiating from it, and those having a number of roots of nearly uniform size extending from the part of the plant lying just beneath the surface of the soil. The former is called tap-root and is illustrated by the roots of such plants as the common clover; the latter are fibrous roots, illustrated by roots of such plants as common grasses. Tap-rooted plants are as a rule deeper growing than those having fibrous roots. This fact is sometimes of practical value in selecting a crop for very shallow soils, or for a rotation between shallow and deep-rooted plants.

How root-hairs take water from the soil. — Root-hairs have been referred to the absorbing organs of the root.

4:

Diagram of simple apparatus for demonstrating osmosis,

A. Tube.

B. Sugar solution within tube.

C. Water

D. Membrane — lima bean skin — separating sugar solution from water.

E. Cardboard sup-

The way in which these hairs are able to absorb water from the soil may be illustrated by a simple experiment. If a bladder with a glass tube securely fastened into its neck is filled with a solution of sugar and then immersed in water with the tube above, the solution will begin in a short time to rise in the tube. This action is known as osmosis. It always takes place when two liquids of different as densities, like water and sugar solution, are separated by a membrane through which water may freely pass. The water flows toward the liquid of the greater density, as in the above instance where it enters the bladder containing the sugar solution, or denser liquid, causing it to rise in the tube. The root-hair may be regarded as a small sac filled with a liquid somewhat denser than water. When the root-hair comes in contact with soil water some of the water passes into the root-hair just as water would enter a bladder filled with sugar solution. The water then proceeds from the root-hair into the root, and thence into the various parts of the plant.

Plants need air. — If a plant is deprived of air it soon dies. Not only does the air furnish carbon dioxide for the starch-making, but it also suppHes oxygen in much the same way as is done in our own bodies. Oxygen is needed by all parts of the plant all the time. The parts of the plant above ground are surrounded by air and have air currents freely moving among them, so that they are at all times abundantly suppHed with oxygen. The roots, on the other hand, being below ground and having only a small supply of air, may fail to get sufficient oxygen or may fail to have the supply, renewed often enough to remove injurious gases as they accumulate in the soil spaces. An example of the effect of insufficient air on the growth of plants may be seen in the low wet spots in a field where some crop such as corn is growing. Plants in these wet spots are generaffy undeveloped and weak, and often die. This is because the water with which the soil is saturated has cut off the air supply from the roots, thus depriving them of oxygen.

How to help plants grow. — We have seen that plants require sunlight, air, water, and certain substances dissolved

HELPING PLANTS GROW 7

in soil water. Our problem is to make conditions as favorable as possible for plants to meet these needs. A study of them will show that we have little or no control over sunshine and the air above ground. The chief way for us to help the plant therefore is through the soil. By means of various farm operations on the soil it is possible to control, to a considerable extent, the water supply and the air needed by the roots, and to furnish material containing such chemical elements as nitrogen, phosphorus, and potassium, in accordance with the needs of the plant.

This fact suggests the soil as the most appropriate subject to consider next in our study of agriculture. It is so important that we must study it in detail. Especially should we know what it is and how it is related to water supply, to air, and to plant food.

Chapter II The Soil

In the preceding chapter attention was called to the fact that some of the needs of the plant, such as sunshine, were beyond our control; while others — relating to the work of the roots — could be controlled through the soil, by making conditions more favorable. The effect of soil condition upon the entire plant is recognized by everyone who is familiar with growing plants. When the condition is poor, as in hard, dry soil, the effect is seen upon the entire plant. The roots, in such cases, are unable to do their work well. Consequently, the whole plant suffers. On the other hand, when the condition is good, as in granular, moist soil, the whole plant is well-developed and vigorous. The roots have access to air and are able to remove readily from the soil the water and material in solution needed for the growth of the entire plant.

Since so much in plant production depends upon the soil, it is necessary to understand the most important facts concerning it — what soil is, where it comes from, and the different kinds of soil.

What soil is. — By soil is generally meant the loose topcovering of the earth. If a small portion of this substance be placed in a bottle of water, well shaken and then allowed to settle, it will be seen to be made up of particles of different sizes. The larger particles will be found at the bottom, smaller ones next, and so on to the very fine particles that

THE SOIL

J>

VHe

Diagram illustrating relation of soil to sub-soil.

A. Soil, B. Sub-soil.

C. Underlying rocks.

remain for a while in suspension. Some small pieces of dark

material will probably be noticed floating on the surface of

the water. The larger particles are

sand; the fine particles, silt; the

very fine particles, clay; the float- ;"; '

ing bits of dark material, organic .'

matter, or humus. Sand, silt, and

clay are rock particles, differing

mainly in size. Organic matter, 1-

or humus, is the remains of decayed —

plants or animals. ~

Where soil comes from. — A

long time ago the upper surface of the earth was solid

rock, and in some places this condition still exists. By action of wind and rain, heat and cold, plants and animals, and other agencies, many of the rocks have been broken into particles small enough to be washed away by water or blown about by winds. Through a long period of thousands of years these processes have been going on.

The rocks on higher places like mouncomposed tains and hills have been broken up, and the small fragments have been carried to lower levels by water and wind,

where they were left to form the soil as we see it. In the

meantime, plants have grown and died and their remains have

become mixed with the rock particles. This fact accounts

for the presence of organic matter, or humus, in the soil.

Diagram of soil particles enlarged.

A. Sand.

B. Granule of very fine particles.

C Air space.

lO

Loss of soil by the action of water. — The same processes that made the soil are continuing today. Material from higher levels is constantly being removed by water to lower levels. This not only appKes to the wearing away of rocks, but to that of the soil itself. One has only to observe the effect of a rain to see how readily the soil is washed from a hillside. The soil particles are carried by the smaher streams into the larger ones, and so on, until finally some are swept

An illustration of erfect of erosion on a field. (U.S. Dept. of Agriculture.)

into the ocean. But all along particles are left by the water; by the slow waters in bends, on level stretches, and at the edges of the streams, especially as the waters of the streams get lower and the currents less swift.

If the bottom land which has recently been covered with the water from an overflow of a stream is examined, it will be seen to be covered with fine sand and silt left there by the receding waters. This deposit has come from the land of

THE SOIL II

higher levels. The total amount of soil thus carried away is very great. It is claimed that if all the soil particles carried by the waters of the Mississippi River in one year were made into a solid rectangular block, it would cover one square mile and be 268 feet high. The amount of soil carried away by water varies with the slope of the land; the steeper the slope, the swifter the water current, and therefore the greater the quantity of soil material carried away. In hilly lands the loss of soil from the uplands is considerable, so much, indeed, that measures need to be taken to reduce the loss.

Kinds of soil. — The size of the particles which make up the soil varies greatly. In some places most of the particles are sand, as in a sandy soil. In others, clay particles are most abundant, as in clay soil. Sometimes particles of clay and silt make up about half and sand the other half. Such soil is called a loam. If the mixture contains somewhat more fine particles than sand, the soil is known as a clay loam; but if more sand than silt and clay, it is called a sandy loam. These names, sandy, clay, loam, clay loam and sandy loam, are in common use in describing soils.

We should now turn back and read again the first paragraph of this chapter and notice especially the last sentence in the paragraph. Rock particles alone, although they make up the soil mass, do not constitute a fertile soil. Air, water, and material for plant food are equally essential for plant growth. For this reason each of these should be considered in its relation to the soil, on the one hand, and to the plant on the other. In the next few chapters we shall try to learn something more about these relations.

CHAPTER III SOIL WATER AND SOIL AIR Water in the Soil

Why water is needed. — The importance of water for plant use has already been intimated in Chapter I. It is not only directly useful in the various ways noted in that chapter, but it has indirect benefits upon plant life almost as great.

Water is a great solvent. That is, it has the power of changing substances from a solid condition to one known as a solution. A lump of sugar placed in a glass of water soon disappears as a solid. The sugar is held invisibly in some way by the water, for we know that water in which sugar is dissolved tastes sweet and when evaporated leaves a solid residue of sugar. This property of water — acting as a solvent — enables it to dissolve certain sohd substances of the soil so that they may pass in solution into the plant, the only possible way for them to enter. The same property enables the water to carry dissolved material from place to place in the soil, as from the depths to the surface when the water moves upward.

Water also brings about changes in the position of the soil particles with reference to one another, making the soil in some instances granular, and in others more compact. This fact will be kept in mind as a further consideration of the action of water in the soil since it is an important one in connection with soil management.

Water has another property that is of importance in soil management. It has a large capacity for absorbing and retaining heat. This property is made use of in heating buildings by hot water systems. Water once heated remains hot for a long time, giving off heat slowly, but in sufficient quantities to keep the rooms of a building warm. Another illustration is found in the influence of large bodies of water,

Diagram showing regions of capillary and free water. Note distribution of roots in area of capillary water.

such as the Great Lakes, in tempering climate, making the shore regions warmer in winter and cooler in summer.

Water in the soil influences its temperature — an important matter in crop production, especially in early spring when heat is needed to start plants to growing. Soils having a large capacity for holding water are called cold soils, because when filled with water which takes up heat slowly they remain cold long after soils having less capacity for holding water have become warm. Heavy clay is an example of a cold soil; it is not the clay but the water held by the clay that makes it slow to heat. Sandy soil, on the other hand, which holds but little water, is regarded as a warm soil.

Another use for water in the soil is that it meets the need for moisture of certain microscopic plants, chiefly bacteria, that are always present in fertile soils. These organisms need water quite as much as other forms of life.

How water is held by the soil. — In order to understand how the soil holds water, we must keep in mind the fact that it is largely made up of particles of rock. These particles are irregular in shape and size, so that spaces are left between them. The arrangement may be suggested by thinking of a number of rocks and bricks thrown loosely together. Here spaces of various sizes and shapes occur among the rocks and bricks just as they occur among soil particles, differing only in size. When these spaces are filled with water, the water is known as free water. When water appears at the surface of the soil or at lower levels, as when a hole in the ground becomes filled with water from adjoining soil spaces, it furnishes an example of free water.

W"hen water clings to the surface of soil particles and is held in the sharp angles between them, but does not occupy the spaces, it is known as film or capillary water. If a pencil is dipped in water, the part coming in contact with water will become wet. Here the solid substance of the pencil attracts and holds a thin layer of water on its surface. It is m a similar way that solid particles of the soil hold films of water on their surfaces. Capillary water is important because it is almost exclusively the form of water used by the plant. When the spaces of the soil in which the root of a plant is growing are filled with water, the air supply is cut off from the roots and the plant suffers. It is largely for this reason that the water of the soil in the region of the roots should be capillary or film water, and not free water.

Amount of water held by the soil. — We have seen that roots of plants rely on root-hairs to secure water and that the water must be in the form of capillary or film water. The quantity of capillary water held by the soil is important, for the amount that can be removed by the plant will depend upon the supply within easy reach of the roots.

Soils differ greatly in their capacity to hold capillary water^ due to differences in the size of soil particles. If a piece of solid substance one cubic inch in size is put in water and then removed, a certain amount of water will adhere to each of its six sides or surfaces. If the cube be cut in half, it will present two additional surfaces capable of holding a layer of water. By dividing the cube its power for holding film water is increased, although the amount of soKd material remains the same. Each division adds more surface; the greater the number of divisions, the greater the total surface provided for contact with water. The total surface of all the particles of a cubic foot of sandy loam has been estimated at 1.39 acres; of clay, 3.54 acres.

A certain mass of coarse particles, such as sand, will have less total surface than a similar mass of silt or clay which consists of finer particles. Consequently, sand will hold less film water than either silt or clay. This fact is easily demon-

Diagram showing relative amount of surface exposed by sand and clay.

A. Sand. B. Clay.

strated by filling two tin cans of the same size, having perforated bottoms, one with dry sand, the other with dry, clay soil. After weighing, each can is saturated with water, and then allowed to drain. The water held in each can after draining will be mostly film water. When weighed again, the amount of film water in each may be determined by subtracting the first weight from the second. It will be found that the clay or fine soil has held more film water than the coarse soil. Sandy soil has a low water-holding capacity compared with clay or clay loam; its capacity may be increased by adding organic matter, such as manure, which retains a great deal of water.

Clay and clay loam, because of the fineness of their particles, retain relatively a large amount of film water, but they have a tendency to bake and become hard and cloddy after a rain. This tendency makes such soils difficult to handle. They are sometimes called heavy soils, not because they are really heavy but because they are hard to work. This is a serious difficulty, but one that may be overcome, in a large measure, by modifying the soil structure in such a way as to make it retain its capacity to hold water and, at the same time, make it more easily handled.

How water moves downward in the soil. — When rain falls or snow melts the water has a tendency to move downward or percolate through the soil. This movement proceeds until the level of the free water below, known as the water table, is reached. As the free water accumulates, the water table rises until finally the upper surface of the soil is' reached. The soil is then saturated, all the spaces being filled with water. When more rain falls, the water either runs off or stands in puddles. This condition frequently occurs in early spring after the spring rains or melting of the winter snows. As the water near the surface evaporates or drains off, the water table is lowered leaving in the upper part of the soil only capillary water, the presence of which is favorable for seed germination and plant growth.

The free water acts as a reservoir to be used later by the plants in the growing season when there may be less rainfall. It becomes important, therefore, to get a sufficient supply of free water into the soil during the time of heavy rains. We need to know in this connection something about how water moves downward in the soil, in order that measures may be taken to secure the greatest benefits from water that reaches the soil.