Field crops

Preface

The extensive use of the previous edition of Field Crops indicates that it fulfilled an acceptable mission when agricultural courses were being formulated and a text of this character was most needed. The study of agriculture has recently received from educators and governmental authority a new impetus on account of the economic importance of crop production. The study of field crops will, therefore, be undertaken more widely than ever before and with a keener appreciation of its value in the national welfare.

In order to be fully apace with matters of figures and fact, a thorough revision has been made of all those parts of the text where experience has suggested improvement or changes of statistics or conditions have made it necessary. It is now believed that it contains the latest available information and practice with reference to the subjects treated. At no other time has there been so national a demand for the specialized teaching of agriculture. It is hoped that this text in its present form will commend itself anew as adapted to the peculiar requirements of these intensive times.

Field Crops has been prepared for students of high school grade and for those in many other public and private agricultural schools and. colleges that desire to teach practical scientific courses in agriculture. Not only as regards subject matter but with special reference also to the language and style of presentation the book has been adapted to the comprehension and interest of the student. It is more personal than bookish.

The work is intended to cover the period of the school year. The time spent upon it, however, may be reduced to a semester by omitting the study of those crops which may be less dominant in the interest of a local community and by limiting the number of exercises that are undertaken.

The study of Field Crops does not presuppose a previous course in botany or general science.

Supplementary references have been given at the close of each chapter in the way of Farmers' Bulletins, which may be obtained free from the Department of Agriculture, Washington, D. C, and of standard volumes which should find a place in the school library. The publications of local experiment stations should also be obtained.

The laboratory exercises and field projects which appear at the close of the chapters are merely suggestive, as it is thought that the local conditions and the individual judgment of the teacher will in most instances determine the character of the experiments. In each classroom special emphasis should be given to the particular crops which are of importance in the region where the instruction is given. Frequent visits should be made to farms in the vicinity, and as many of the crops as possible studied at first hand. Small plats of some crops not common in the community may well be grown on the school farm to supply illustrative material.

While the book is designed primarily for text use, the authors trust that it will also be of interest to farmers and to those who desire to become farmers. The results of many^ experiments have been embodied in the text, as have also the practical experiences of many good farmers. The aim throughout has been to make a simple, practical, readable manual.

Our acknowledgments are due to various officials of the United States Department of Agriculture, and to the Ohio, Kansas, and Minnesota experiment stations for illustrative material.

A. D. WILSON.

C. W. WARBURTON October 1, 1918.

PART I— INTRODUCTION Chapter Page

I Classification of Crops 11

Definition of Terms. Classification of Crops. Relative Importance. Description of Classes. Uses of Crops. Choice of Crops. Diversification.

II The Growth of Plants. 23

The Seed and Its Germination. What the Leaves Do. The Roots and Their Uses. Elements of Plant Food and Their Uses. The Production of Seed.

Part Ii— Grain Crops

m Com. 46

Origin and Description. Classification. Importance. Soils and Fertilizers. Preparation of the Soil. Preparation of Seed for Planting. Planting. Cultivation. Harvesting. Fodder Corn. Corn for Silage. Marketing and Returns. Corn in Crop Rotations. Selection of Seed Corn. Storing the Seed. Uses. Diseases and Insects. Improvement. Judging.

IV Wheat. . 123

Description and Classification. Importance. Soils and Fertilizers. Growing the Crop. Harvesting and Threshing, Marketing and Market Grades. Prices and Cost. Relation to Other Crops. Uses. Diseases and Insect Enemies. Methods of Improvement.

V Oats 163

History and Description. Importance. Production. Harvesting. Marketing and Returns. Rotations. Uses. Insects and Diseases. Improvement.

VI Barley 197

History and Description. Importance. Production. Harvesting. Marketing and Returns. Relation to Other Crops. Uses. Insects and Diseases. Improvement.

Vn Rye. 217

Origin and Description. Importance. Production. Growing the Crop. Uses. Diseases.

Vni Flax. 225

History and Description. Importance. Growing the Crop. Harvesting and Handling. Market and Returns. Diseases and Insects. Rotation. Uses. Improvement.

Chapter Page

IX Miscellaneous Grain Crops 237

Rice. The Grain Sorghums. Broom Corn. Buckwheat. The Millets.

PART III— FORAGE CROPS X Introduction 253

Definitions. Importance. Classification. Forage Production. Uses of Forage. Essentials of a Forage Crop. Feeding Value.

XI The Making of a Meadow . . 260

Essentials. Form_ation of a Meadow. Sowing in Mixtures. Preparing the Land. Selection of the Seed. Germination Test. Time to Sow. Use of Nurse Crop. Seeding. Important Meadow Plants. Care of the Meadow. Permanent Meadows and Their Improvement. Place in the Rotation.

[ XII Hay and Hay-Making ^ 271

Hay Plants. Production of Hay. Acre Yield and Value. Time to Cut. Method of Cutting. Curing. Machinery. Storing. Baling. Measuring. Market Classes.

XIII Pastures i 281

Importance. Essentials. Formation of a Pasture. Pasture Plants. Improving Native Pastures. Management of Pastures. Renovating Old Pastures.

XIV The Grasses 287

Definition. General Characters. Differences. Reason for Importance. Comparative Value of Different Grasses.

XV Perennial Grasses 291

Timothy. Kentucky Blue Grass. Redtop. Orchard Grass. Bermuda Grass. Johnson Grass. Brome Grass. Wheat Grasses. Fescues. Rye Grasses.

XVI Annual Forage Grasses 315

The Sorghums. Sudan Grass. Foxtail Millets. Other Millets. The Small Grains.

XVII The Legumes 327

What Legumes Are. General Characters. Differences. Importance. How the Legumes Gather Nitrogen. Nitrifying Bacteria. Inoculation.

XVIII The Clovers 333

Red Clover. White Clover. Alsike Clover. Crimson Clover.

XIX Alfalfa 351

Origin and History. Description. Varieties. Production. The Yield. Soils and Fertilizers. Preparation of the Land. Sowing the Seed. Time of Seeding.

CONTENTS

XX

Chapter p^

With a Nurse Crop. Inoculation. Treatment of Meadows. Making the Hay. Harvesting. In Rotations. Use of Hay. Alfalfa for Pasture, Soiling, Meal. Insects and Rodent Pests. Diseases. Weeds.

Miscellaneous Legumes 357

Cowpea. Soy Bean. Peanut. Field Pea. Field Bean. Sweet Clover. Bur Clover. Japan Clover. Vetch. Velvet Bean.

XXI Root Crops 339

Mangels. Carrots. Turnips and Rutagabas.* Cabbage and Kohl-rabi. Rape and Kale.

xxn xxm

XXIV

XXV

XXVI xxvn

PART IV— MISCELLANEOUS CROPS Root and Tuber Food Crops 399

The Potato: History and Classification, importance, Soils and Fertilizers, Production, Harvesting and Storing, Marketing, Rotation, Diseases and Insects, Improvment. The Sweet Potato: Description, Importance, Soils and Fertilizers, Method of Production.

Sugar Plants 426

History and Description. The Sugar Beet: Importance, Culture, Production of Seed, Manufacture of Sugar, By-Products. Sugar Cane: Characteristics, Countries Which Produce. Propagation, Soils and Fertilizers. Production, Extracting the Juice, Making the Sugar.

Fiber Plants 437

Cotton: Description and Classification, importance, feoils and Fertilizers, Growing the Crop, Marketing and Returns, Uses, Diseases and Insects. Flax. Hemo Other Fiber Plants.

Tobacco 4g J

Origin and History. Botany. Composition. ' Types. Importance. Soils and Fertilizers. Preparing the Seed Bed. Sowing the Seed. Preparing the Field. Setting the Plants. Cultivation. Topping. Harvesting. Curing. Stripping and Grading. Marketing. Returns Rotation. Insects and Diseases. Selection of Seed.

PART V— CONCLUDING CHAPTERS Rotation of Crops 475

Definition. Origin. How Rotations Help. What a

Rotation Should Contain. Suggestive Rotations. Weeds 493

Definition. Need of the Study.' ' Classes *of Weeds.

Damage from Weeds. Benefits from Weeds. How

Weeds Spread. Methods of Eradication.

Chapter I Classification Of Field Crops

1. Introduction. The cultivation of crops is one of the first evidences of a permanent civiHzation. Savages Uve on the spoils of the hunt and on such fruits, nuts, and other vegetable products as nature supplies. Some of the wandering tribes in the beginnings of civilization domesticated the horse, the ox, and the sheep; but these animals were herded on the natural pasture lands, and the tribes moved from place to place with them as the grasses furnished or failed to furnish pasture for their herds and flocks. The next stage in civilization was the growing of plants for their seeds and fruits to assure the food supply of the tribe and to furnish forage for the domesticated animals. A natural result of this production of crops was the storage of these products for use during winter and against times of famine. Crop production required a more or less fixed habitation for men, as the crop had to be protected from the depredations of animals and of hostile tribes from the time of its planting till harvest, while permanent storehouses for the food supply had to be built and guarded. The building of permanent habitations and the beginnings of home life can thus be traced directly

to the cultivation of crops.

2. Agriculture and Horticulture. Agriculture, in the original sense, meant field culture, while horticulture meant the growing of crops within a garden or inclosure. Both words are from the Latin. The difference in terms is due to the fact that the Roman farmers hved within walled inclosures, the better to protect themselves and their stores of food from their enemies. The larger areas in crops, the food grains and the forage for animals, were outside the walls, and the tilhng of these crops was agriculture, from ager, field, and cultura, culture or cultivation. The fruit and vegetable crops, which required only small areas and were given special care, were grown within the walls and their tilling was horticulture, from hortus, yard or inclosure, and cultura. In modern times, however, agriculture has come to have a broader meaning, including all the operations of the farm, such as stock raising, the production of field crops, horticulture, and the manufacture of dairy and other products. The tilling of the soil and the production of field crops are now usually included under the term ''agronomy."

3. Cultivated Plants. The number of cultivated plants other then ornamental, according to De Candolle in his ''Origin of Cultivated Plants," is about two hundred and fifty. Of these, four fifths are natives of the Old World. Seventy-seven are cultivated for their fruits, sixty-six for their seeds, and sixty-five for their stems or leaves.' Most of the remainder are grown for their underground parts, which may be thickened roots, as the beet, or tubers, as the potato.

4. Field Crops. In this book, only those crops which are ordinarily grown in large areas under field culture (the "agriculture" of the Romans) are included. In general, extensive rather than intensive methods are used in the cultivation of field crops. This rule does not always hold true. The most careful and intensive methods are used in the culture of sugar beets and of some types of tobacco, while fruits and

CLASSIFICATION OF FIELD CROPS 13

vegetables that find a wide market are sometimes grown in large areas by extensive, or field, methods.

5. Classification of Field Crops. It is rather difficult to make a definite classification of field . crops, for certain uses may be made of a certain crop under one set of conditions and other and very different uses under another. New uses are continually being made of the various crops, so that a classification made now might be materially wrong in a few years. The principal field crops can, however, be included in some one of the following classes: Grain, hay and forage, fiber, tuber, root, sugar plants, and stimulant. This classification is based in part on the portions of the plants which are used, and in part on the uses to which they are put. Medicinal plants and a few others of a miscellaneous nature are not grown to any considerable extent and need not be considered at length.

6. Relative Importance. The 1910 census reports show that the total area in field and garden crops in the United States was, in 1909, 311,000,000 acres, of which all but about 10,000,000 acres were in field crops. These 10,000,000 acres were devoted to garden and orchard crops. The total area of improved farm land was more than 478,000,000 acres, leaving something like 167,000,000 acres in pastures and improved woodlands. Of the 311,000,000 acres in field crops, about 191,000,000 acres, or about 61 per cent, were in grain crops; 72,000,000 acres, or about 23 per cent, in hay and forage crops ; about 10 per cent in fiber crops, and the remainder in tuber, root, sugar, stimulant, and miscellaneous crops.

VALUE AREA

FORAGE HBI^HH FIBER ■■ ALL OTHERS ■

Figure 1. — Relative areas and values of the important classes of farm crops.

m

Of the total value of $5,487,000,000 for all crops, as reported for the Census of 1910', approxhnately $2,746,000,000 or 50 per cent, was gram crops; $824,000,000 or about 15 per cent, hay and forage crops; and $825,000,000, or about

15 per cent, fiber crops. The estimated value of all grain crops in 1917, according to the Federal Bureau of Crop Estimates, was $7,211,000,000, due to greatty increased prices for all farm products. The value of the cotton crop was $1,517,000,000 and of the hay and foragecrop, $1,567,000,000. Assuming that the grain, cotton, and hay crops in 1917 represented 80 per cent of the value of all crops, as was the case in 1909, the total value of all crops in 1917 was approximately $13,620,000,000, about 148 per cent more than in 1909. Dividing the total value of crops in 1909 by 6,361,502, the number of farms in the United States that year, gives an average value of crops per farm of $863, as compared with $523 per farm in 1899.

7. Grain Crops. A grain crop is one which is grown principally for the production of its seeds. The most important grains are the cereals, which are grasses grown for their seeds. The principal cereals in the United States are corn, wheat, oats, barley, rye, and rice. Millet and sorghum are also cereals, though some types of these two crops are grown for forage rather than for grain. Buckwheat and flax are the only important grains which are not cereals, unless such crops as peas and beans are included. Field peas, cowpeas, and soy beans are usually grown for forage or green manure, but may be harvested for their seeds. The area in corn, wheat, oats, barley, rye, fiax, rice, and buckwheat in 1909, according to the Census figures, was 191,300,000 acres; the total production was 4,500,298,000 bushels, and the total value, $2,726,827,000. In 1917 these figures for the same crops were increased to 225,984,000 acres, 5,728,939,000

iThe census is known as the census of 1910, but the figures of crop yields and values are for the previous year, 1909.

GRAIN CROPS bushels, and $6,881,900,000, respectively. The acreage, production, and value of each of these crops in 1917 are shown in Table I.

Table I. Acreage, production, and value of each of the important grain crops in the United States in 1917, and the total for all grain crops.

Crop

Value

Corn

119,755,000

45,941,000

43,572,000

8,835,000

4,102,000

964,000

1,809,000

1,006,000

225,984,000

3,159,494,000

650,828,000

1,587,286,000

208,975,000

60,145,000

36,278,000

8,473,000

17,460,000

5,728,939,000

4,053,672,000

Oats

Barley

Rye

Rice

Flax

237,539,000

100,025,000

68,717,000

25,148,000

Buckwheat

Totals

The improved farm land in the United States in 1909 was 477,424,000 acres. Of this total, 40.09 per cent was m grain crops, as follows: Corn, 20.61 per cent; wheat, 9.28 per cent; oats, 7.36 per cent; barley, 1.61 per cent; rye, 0.46 per cent; flax, 0.44 per cent; buckw^heat, 0.18 per cent; and rice, 0.15 per cent. The acreage of improved farm land in 1917 is not definite^ known, but it was of course larger than in 1909. The acreage of wheat in 1917 was abnormally low on account of losses from winterkilling. Otherwise,

Table II. The relative importance of the corn, wheat, oats, barley, and other grain crops of the United States, as indicated by the percentages of the total acreage, production and value of all grain crops in 1917.

Crop

Corn

Oats

Barley

Other Grains in bushels in pounds

52.99

55.15

62.50

20.33

11.34

13.79

19.28

27.71

17.94

3.91

3.65

3.54

3.49

2.15

2.23

Value

58.90

19.00

15.42

3.45

3.23 the proportionate acreage in the various crops was about the same as in 1909. The percentage of each of the important grain crops in 1917 as compared with the total of all grains in acreage, yield, and value are shown in Table II.

Figure 2. — Abundant farm crops and prosperous, well-tilled farms result when grain and stock farming are wisely combined.

8. Forage Crops. Next to the grains, forage crops are of most importance. A forage plant is one which is fed to stock in the green state or when cured into hay or fodder. The leaves and stems of the whole plant may be used. In addition to the harvested hay and fodder crops, this class includes the pasture .plants. The total area in harvested forage crops in 1909 was 71,915,000 acres, or 15.06 per cent of the total acreage of improved farm land. The production of hay and forage was 97,147,000 tons, and the value of this forage was $822,476,000. No definite value can be placed on the acreage in pasture, which is much greater than the acreage in harvested forage crops.

FIBERS, TUBERS, ROOTS 17

Nearly all forage crops may be included in one of two general classes, the grasses and the legumes. The first includes timothy, blue grass, redtop, brome grass, Bermuda grass, Johnson grass, and all similar crops; the legumes include such crops as alfalfa, red clover, white clover, cowpeas, soy beans, Japan clover, and field peas. Most of these are grown ordinarily for forage, either as hay or pasture crops, though a few, such as field peas, cowpeas, soy beans, field beans, and peanuts, may be grown for their seeds.

Of the nearly 72,000,000 acres in harvested hay and forage crops reported by the Census of 1910, 27.17 per cent was in mixed timothy and clover meadow; 23.45 per cent in wild, salt, or prairie grasses, and 20.4 per cent in timothy alone. Alfalfa occupied 6.54 per cent of this area; clover alone, 3.4 per cent; grains cut green for hay, 5.92 per cent; and coarse fodder, such as sorghum and fodder corn, 5.69 per cent.

9. Fibers. The fiber crops grown in the United States are cotton, flax, and hemp. Of these three, cotton is by far the most important. Its cultivation is confined to the southeastern portion of the country, including Texas and Oklahoma. The cotton crop ranks second in value of all our field crops, being surpassed only by corn, though wheat and hay often almost equal it. Flax is grown principally for grain; its use as fiber is merely incidental. Hemp is produced in a limited way in a few scattered areas.

10. Tubers. The only important tuber crop is the potato, sometimes locally known as the Irish, or white, potato to distinguish it from the sweet potato, which is a root, not a tuber. This is one of our important food crops, the production in 1917 being 442,536,000 bushels, valued at $543,865,000. It occupies about three fourths of the area of improved farm land, and ranks sixth in value among our field crops.

11. Roots. The principal root crop of the United States is the sweet potato, which was grown on 953,000 acres in

1917, with a production of 87,141,000 bushels. Other root crops are grown principally for stock feeding, as the mangel, carrot, turnip, and rutabaga. No figures are given for the annual production of these crops by the Bureau of Crop Estimates, but in 1909 they occupied only 18,916 acres, with a production of 253,533 tons. The sugar beet is a root crop

Figure 3. — A field of well-cultivated sugar beets, our most important root crop.

which has grown to be of great importance for the production of sugar. It is discussed under the heading of sugarcrops in Chapter XXIII.

12. Sugar Crops. Two important sugar crops are grown in the United States, the sugar cane and the sugar beet. Sugar cane is much the older source of sugar. The development of the sugar beet industry in America is comparatively recent, and it is only in the last few years that the production of beet sugar has surpassed that of cane sugar in the United States. The cultivation of sugar cane is limited practically to Louisiana and Texas, though the crop is grown generally over the South for sirup production. The sugar beet is grown over a wide range of country, from New York to California. The production of cane sugar in the

USES OF CROPS 19

United States in 1917 was 235,000 short tons, while that of beet sugar, amounted to 765,000 short tons.

13. Stimulants and Sedatives. The only stimulant or sedative crop which is grown to any extent in the United States is tobacco. This crop was grown on 1,295,000 acres in 1909, or 0.27 per cent of our improved farm lands. The production amounted to 1,055,765,000 pounds, valued at $106,000,000 making it rank seventh in value among our field crops.

14. Miscellaneous and Medicinal Crops. None of the miscellaneous and medicinal crops is grown on a large scale. Among them may be mentioned broomcorn, hops, the castor bean, mustard, and various kinds of mint.

15. The Uses of Crops. The principal uses of field croi>s are to supply food and clothing for humanity, to feed animals, to maintain or to restore the vegetable matter and the fertility of the soil and to prevent the loss of fertility through erosion or other means. The principal food crops of the United States are wheat, corn, rice, potatoes, and sweet potatoes. Other crops which are used to a greater or less extent for human food are oats, barley, rye, buckwheat, the sugar beet, and sugar cane. The use of barley, rye, and oats as human food in the United States has increased enormously since our entrance into the world war in 1917. The plants which supply material for clothing are cotton and flax. Many plants furnish food for man indirectly by being fed to animals, to be transformed into meat, butter, and milk. Corn, oats, barley, rye, and the grasses and clovers are the important food crops for the domestic animals which do useful work for man or furnish him with food. Some crops maintain or add to the fertility of the soil by supplying the vegetable matter necessary for the continuance of plant growth. Others, by providing a soil cover which prevents washing, leaching, and other natural losses, help to retain the fertility for the production of useful crops.

16. The Right Crops to Grow. The choice of field crops for a given farm or locahty depends to some extent on the cUmate and soil conditions, the kind of farming, and the proximity of the market. Chmate limits the production of some crops. Cotton, for instance, can be grown profitably only where the summers are long and hot. Winter wheat may thrive where spring wheat is wholly unprofitable.

ill i

^^^g^jr^^aUI^HH'

^m

Figure 4. — By far the largest part of the corn crop is fed on the farm and marketed in the concentrated form of animal products.

Some crops grow best on a sand}^ soil; others, on clay. We can materially change the nature of a soil bj^ tillage, drainage, and the application of fertilizers, so as to make it suitable for many crops, but soil types limit to some extent the growth and profitableness of some of our most important crop plants. The quality and value of tobacco are influenced more by the nature of the soil on which it is grown than by any other factor. It is usually a good plan to follow the general practice of a neighborhood in choosing the crops to grow, though a new crop may sometimes be introduced with profit.

The use which is to be made of a crop is a decided factor in its choice. On a dairj^ farm, forage crops are of prime importance. The selection of these crops and the relative areas to be devoted to them depend on the special methods which are followed. Some crops are suitable for pasture,

DIVERSIFICATION OF CROPS others for hay, and still others for cutting for green feed (soiling). On a farm where beef or pork is produced, the growing of grain is often more important than the production of forage. On a grain or cotton farm, forage production is of Httle consequence, except to furnish feed for the necessary work animals. Market facilities are often a deciding

Figure 5. — On the way to market. Beef represents farm crops converted into a form that is more useful to man.l factor in the selection of crops; for bulky crops like hay might be produced profitably for a near-by market, while the profit would be consumed by the transportation charges if it were necessary to haul the product a considerable distance. It is usually advantageous to market crops in a condensed form. Feeding forage and grain crops and marketing them in the form of live stock or live-stock products help to keep up the fertility of the soil if the manure is utilized, while the expense of marketing is reduced.

17. Diversification. It is not often safe to depend entirely on a single crop. It is sometimes desirable to make a specialty of a crop, and to become known as a producer of high quality oats or corn or cotton or some other product of unusual excellence. This plan often results in materially increased profits, but only a portion of the farm should be devoted to any particular crop each year. It is often the case that unfavorable conditions which cause a partial or complete failure of one crop may be suitable for another. In diversity of crops there is safety. Some of the reasons for diversification and systematic crop sequence are given in the chapter on Crop Rotation.

Domesticated Animals and Plants, Davenport.

Origin of Cultivated Plants, De Candolle.

Cereals in America, Hunt.

Field Crop Production, Livingston.

Productive Farm Crops, Montgomery.

Geography of the World's Agriculture, Finch and Baker.

Chapter II The Growth Of Plants

18. Introduction. It is neither desirable nor necessary to set down in detail the processes which are involved in the germination of seeds and the growth of plants, the uses of the different elements of plant food, and the effects of tillage, drainage, and other factors on crop production. The study of growth processes is more properly a part of the work in botany, while plant food, cultivation, moisture supply, and other subjects of similar nature may best be discussed along with the study of soils. A brief outline of the way in which plants grow, however, should be of value to the student or the producer of field crops, in affording a better understanding of man}^ of the cultural methods and other matters which will be detailed in the discussion of each crop.

THE SEED AND ITS GERMINATION

19. What the Seed Is. A seed is a reproductive body produced by flowering plants. It contains an embrj^o plantlet and usually an amount of plant food, all surrounded by one or more seed coats. Nearly all field crops are grown from seed, though a few, such as potatoes, sweet potatoes, and sugar cane, are grown from divisions of the roots or stalks. The seed consists of a minute plant, the embiyo, and the store of the plant food which surrounds it. This embryo may be seen very readily in a pea or bean. If the seeds of these plants are soaked in water for a few hours, the skin, or outer protective covering, may be removed easily. If the halves are then separated, a minute plantlet will be found adhering to one of them. This is the live portion of the seed, which, under proper conditions, will start into growth and produce a mature plant. This plantlet, or embryo, is attached to both halves of the seed in its natural state, and forms a sort of hinge between them. The embryo consists of two parts, the plumule, which grows upward and forms the stem and leaves, and the radicle, which grows down into the soil and forms the roots. The thick, fleshy portions of the seed consist largely of starch, which, as growth begins, is changed to a form which can be used by the embryo, and which supports the plantlet till it can form roots and leaves of its own and obtain its food from the soil and the air.

20. Good Seed. Seed, to be of value, must be viable, or ''live." Its viability, or power to germinate and produce strong, healthy plants, depends on the plant which bore it, its maturity, its age, and the conditions under which it has l^een kept. The plant which bore the seed must have been strong and healthy, or the seed will be weak and lacking in vigor. Live seed must be fully matured. The embryo is not wholly developed in unripe or immature seed, and the supply of plant food is less than in mature seed. Good seed is usually fresh seed. Crop plants differ greatly in the length of time during which they retain their viability, but the vigor and strength of germination usually decrease rapidly after the seed is two years old. The conditions under which the seed has been kept are also of material effect. Ordinarily, seed should be well cured, and kept in a dry place where it wdll not freeze. Many seeds, however, are not injured by frost if they are fully cured and dry when frozen.

21. Germination. Seeds germinate or start into growth under certain conditions. The essentials for germination are warmth, air, and moisture. There can be no growth below the freezing point, and most seeds germinate very slowly, if at all, below 40 degrees Fahrenheit. The ''optimum" temperature, or that at which seeds germinate best, varies with different kinds of seeds, but the range is compar-