Popular Science Monthly/Volume 73/November 1908/The Rotation of Crops
| THE ROTATION OF CROPS |
By SAMUEL FRASER
GENESEO, N. Y.
THE rotation of crops or the order in which crops are grown upon the same land during a period of years is of such moment to the successful development of our agriculture, and consequently of our national welfare that it must receive consideration. The farm value of our farm products has increased rapidly in the last few years, having risen from $4,717,000,000 in 1899 to $7,412,000,000 in 1907. The figures indicate an increase in value for 1907 of 50 per cent, over 1899. This remarkable growth in the value of farm products is largely due to an increase in the area tilled. Now that the best land is settled, it is essential to increase the productivity of an acre, and as the rotation of crops is one means of securing this result its usage must extend. The use of manure and fertilizers have been recommended and proved to be of value in the eastern states for increasing crop yields. The value of plant breeding and the development of plants which are capable of giving heavier yields and products of better quality has been recognized; and the productions of many workers have added millions of dollars annually to our national welfare. It is safe to say that anything that benefits the farmer and increases his ability to produce wealth is of distinct value to the nation and of direct interest to the world.
A study of the rotation of crops used at any particular period in the history of a nation is of value as a guide to the status of agriculture. Agriculture had its birth in the ages of antiquity, when some mother conceived the idea that she might save herself and her child from famine by growing or affording protection to some of the plants which furnished food. From this time on and for a long time the requirements of the people were scanty, and the crops grown were so few that no rotation could be carried on. Evidence shows that the neolithic people of Europe had the rudiments of agriculture, that they grew cereals, had cattle and were conversant with the arts of weaving, spinning and pottery-making. Among other places, they inhabited the hills of Britain and Ireland, where terraces made by them on the hillsides in Wiltshire and even as far north as the Cheviot Hills and the Grampian Mountains of Scotland are still visible. These races practised irrigation and a system of agriculture something like that now in vogue on the hills of parts of China and among the Coorgs, a hill
It is a Four Course of (1) Corn, (2) Oats, (3) Wheat, (4) Hay—Timothy and Clover. First year. Corn, grown for silage. About 10 tons of silage is cut per acre. Corn permits of intertillage and cleaning the land of weeds.
tribe, in India. The inhabitants of Britain were Iberians, a non Aryan race and related to some of the hill tribes of India. The hills were peopled first because they were free from trees, and the soil was easy to till, while the valleys were swampy, marshy and often covered with timber, which they had no means of removing except by fire. The forests were held to be more or less sacred, even at so late a period as the Roman invasion. The Druid priesthood is held to be of non Aryan origin, but surviving a conquest, was accepted by the Celts. Two Aryan races, the Celts and the Saxons, invaded Britain, one before and one after the time of the Romans and both learned their agriculture from the race they overcame. At this time the community generally owned the land, and its management was vested in officials elected for the purpose. The Romans introduced individual ownership, and this was never uprooted. It grew gradually under the Saxons and more quickly under the Normans, but made its most rapid progress during the fifteenth and sixteenth centuries, when wool was the valuable product and land was wanted for grazing sheep. During this time the customary method was to cultivate a piece of land for a few years and then, leaving it to go back to grass, break up another piece, and cultivate it until it became unprofitable. It is interesting to note that wherever population is scanty this method is adopted, whether in the ages of antiquity in Europe or during the nineteenth century in America. In some parts of the United Kingdom, modifications of this system existed at a comparatively recent date. The
First Year. Corn. Whenever possible part of the crop is grown to furnish corn and the storer (stalks and leaves) are fed to steers and young cattle. The present high price of grain is forcing the farmers to grow more concentrated feeds on their farms.
town of Kells, in Ireland, owns 1,700 acres, which was farmed by the community. About 130 acres were broken up at a time, and were cropped for four years with wheat, beans and fallowed and then seeded to grass and another 130 acres were plowed. Stock was grazed on the untitled land, each citizen having the right to put a certain number of stock on the common. The town of Lauder, in Berwickshire, Scotland, had a similar custom. These examples illustrate some of the methods in use when the Pilgrim Fathers sailed for America, and the rotation of wheat, beans and then a fallow remained the most common in Britain until 150 years ago.
Xenophon speaks of a two years' cropping of wheat and fallow, and Roman writers remarked on the value of growing a leguminous crop before sowing wheat, a fact which remained almost unused until 150 years ago and unexplainable until the close of the last century. Now it is a maxim that at least one leguminous crop shall be grown in a rotation, because such crops have the power of gathering nitrogen from the air in the soil, and their roots and stubble when plowed under enrich the soil in humus to a greater extent than most other crops.
In the early days of this country and in newly-occupied places it was customary to grow one crop, either wheat, corn, tobacco or cotton, as circumstances required, for a number of years upon the same land, until the yield from the crop was reduced to such a point that it became unprofitable. More land was then taken and treated in a similar
Second Year. Grain Crop—Oats. On the Cornell University Farm yields of 50 bushels per acre are often secured.
manner. Such methods are permissible only in a thinly populated country. Some time previous to this some men had noted that in nature the crops grown on a piece of land during a term of years varied, and it is common observation to-day that in the north, hardwood trees, as oaks, will come in where pines have been cut off. Hemlocks do not succeed hemlocks. And even in grass land marked changes occur in the composition of the herbage. During a period of wet years Redtop (Agrostis vulgaris) may assume the ascendancy on a piece of land, and lose it just as quickly when an era of dry years occurs. To secure a rotation of crops, it is essential that crops capable of being grown in a district be known and that there be a market for them. Wheat has been and is the pioneer crop of the northwestern parts of this continent. Climatic conditions are important factors in determining the rotation. In Canada, oats, mangels, clover and timothy may be good crops to include, but they would be of little value for the southern states. Cotton, cowpeas and crab grass would be more likely to grow. It was largely lack of knowledge about crops that prevented progress. Clover and turnips were not grown as field crops in England until about 170 years ago, and even about a hundred years ago, Arthur Young said that probably not more than half the farmers and certainly not over two thirds grew clover, although both turnips and clover were recognized as of value in the sixteenth century, and turnips were used as an article of diet at least as early as 1390. About 1730 Lord Townsend introduced on to his barren estate in Norfolk what has
Third Year. Wheat. Preparing Land for Wheat. The last harrowing is being given. A fine tilth has been obtained as evidenced by the cloud of dust which obscures the horses' feet, the harrow and the man. Certain crops permit the disintegration of the soil particles by tillage.
since become known as the Norfolk four-course rotation, consisting of turnips, barley, clover, wheat, and yet, in spite of the most gratifying results, it took seventy years of demonstration before this system of rotation spread over the county of Norfolk. Dickson, of Edinburgh, Scotland, wrote a treatise on the rotation of crops in 1777 and in 1788 Marshall, of England, stated that a common rotation was: first year, wheat, barley or bigg; second year, oats, beans or pulse; third year, fallow. Although the value of a rotation of crops was known to Camillo Tarello, who urged the adoption of such a system in agriculture in 1566, before the senate of Venice, it was little understood elsewhere. Tarello was far in advance of his time and gave a list of the advantages of a rotation, somewhat similar to those known to-day. Yet his careful experiments remained unknown and little used until similar facts were discovered elsewhere. In Great Britain, previous to the translation of Tarello's article and the issue of other works during the eighteenth century, the subject of rotation was generally passed over by reciting courses which might be good, bad or execrable, as though their arrangement were devoid of principle and had absolutely no relationship with the economical management of a farm. That poverty in an agricultural community might be due to a poor rotation of crops and success due to a good one never occurred to the minds of those who ought to have been interested. The value of carrying live stock to consume part of the crops grown had not been recognized, and
Fourth Year. Hay—Timothy and Clover. In 1903 the grass field was mown twice and yielded 513 tons of hay per acre in two cuttings. In 1904 one field yielded 412tons per acre, the first cutting.
the truth of the proverb—"No grass, no cattle; no cattle, no manure; no manure, no crops"—had not been appreciated. Townsend's four course considered something more than supplying man with grain, a new point of view arose, and in regard to it Arthur Young said: "The grand article of all husbandry is the keeping great stocks of cattle; for without much cattle, there can not be much manure." Two out of the four crops, clover and turnips, and the straw from the grain crops were used for the live stock, either as food or as bedding and the result was a large supply of manure and increased productivity of the soil. The grain crops were separated either by an intertilled crop, turnips, or by a legume, clover. Substituting corn for turnips we have a rotation of equal value for the northern states.
The introduction of clover and turnips into England as field crops is coincident with the improvement of live stock by Bakewell. From this time on meat was added to the diet of the common people of Britain, in small but increasing quantities. It is worth noting the effect that the call for meat had upon the minds of the thinkers of two divisions of the Teutonic race. The English school—including Bakewell, Coke of Holkham, Booth, Bates and many others—set to work to so improve the conformation of their breeds of live stock that they should be capable of producing a pound of beef, mutton or milk more economically; while the German school, led by von Thaer, began the epoch-making research as to the influence of foods upon their live stock, their efforts being to make the foods produce meat more economically.
Livestock is a Necessity on a Self-sustaining Farm. Frequently the four-course rotation used on the Cornell University Farm could be profitably made into a five-course, by retaining the grass for two years, making hay the first year and pasturing it the second.
Thus the one school improved the animals, hut paid less attention to the foods, while the other made the ration the primary consideration. Lancaster County, Pa., has made history both for its productivity and its rotation of crops. The two are inseparably connected. Corn, oats, wheat and clover and timothy are grown in the above mentioned order, and the farmers of this vicinity, realizing the value of manure, have purchased western live stock and corn and with the roughage grown have fattened the stock and made money. The object of a rotation should be to convert sunshine into dollars, in such a manner that the soil used shall be as productive at the end thereof, if not more so, than it was at the beginning.
Wheat or corn growing employs a minimum amount of help for short definite portions of the year. Mixed farming, where live stock is kept, requires the retention of help throughout the year, and in this way it is of social importance, a floating population being a serious menace to a nation.
Where the one crop, as wheat, is grown, there is much more trouble in maintaining the soil in good physical texture. When clover is grown, the stubble and roots plowed under increase the amount of organic matter in the soil, which upon decaying forms humus. Humus aids in developing bacterial activities in the soil, the importance of which is now recognized, although feebly understood. The strong taproots of such plants as clover or alfalfa upon decaying leave air passages in the soil and subsoil, which are of great value in aeration, and render the soil more habitable for certain useful bacteria and more permeable to moisture and roots of succeeding crops.
Constant tillage of most soils may make the particles so small that they tend to run together in wet weather and bake into a hard mass upon drying. Putting land into grass for a few years permits the aggregation of soil particles and in this way a rotation corrects injuries.
Fields in grass are less expensive to work than the same area under intertilled crops as potatoes, or roots, hence a mixed farm can be managed well on less capital than one entirely under tillage. If grass can not be grown, alfalfa may be. Alfalfa is usually left undisturbed for several years and like other legumes produces marked increases in the succeeding crops. At Rothamsted Experiment Station, England, land which has been growing leguminous crops for fifty years was plowed up in 1898 and sown to wheat for the five following years with the result that the average annual yield per acre for this period was 27 bushels on the alfalfa plat, 24 bushels after white clover, 23 after red clover and sainfoin, 22 after sweet clover and 20 after peas, beans or vetches, while on the plats growing wheat and fallowed on alternate years for the same length of time, the yields averaged 7.5 bushels per acre per annum during the five years under consideration.
Grain crops as commonly grown do not permit of intertillage, hence the land is liable to become weedy. Intertilled crops can not be successively and profitably grown for a series of years unless they are specialties and bring high prices, as truck crops near towns. Under these circumstances special care is taken in manuring and fertilizing and in combatting insects and diseases. Constant intertillage depletes the soil of its organic matter, the trucker puts this back in his manure. At the Cornell University farm, which is run as a dairy farm, the four-course rotation of (1) corn (land manured about 8 to 10 tons per acre) cut for silage, (2) oats, (3) wheat (manured 8 to 10 tons per acre) and (4) clover, 10 pounds, and timothy, 15 pounds of seed (sown in the wheat), mown twice, has been quite valuable in bringing a poor unproductive farm into a high state of productivity. About 10 tons of corn silage is grown per acre, 50 bushels of oats, 30 to 40 bushels of wheat and over 5 tons of hay per acre (two cuttings). The root residues and the manures applied have been sufficient to preserve and augment the humus content of the soil.
Many plant diseases and insect attacks are easy to combat if a good rotation be adopted. These troubles have and will do more to enforce the consideration of a rotation of crops than almost any other factors. During the year 1904 in trials of mangels on the Cornell University farm the value of a rotation of crops was shown. Two plats separated by others had been growing mangels for three years. In 1903 the leaf spot disease (Cercospora beticola) was prevalent. In 1901 the crop was sown on these and on plats which had been in corn in 1903 and other crops previously. The disease attacked the beets on the "no rotation" plats early in the season, and many rows had to be resown. The yield per acre was 9.5 tons containing one ton of dry matter, value $20. The yield per acre on the rotation plats was 331⁄2 tons containing four tons of dry matter, value $80, a clear gain of $60 per acre from the rotation of crops.
Different crops require different amounts of water to make a pound of dry matter, that is, some transpire more than others, thus oats will transpire 500 pounds, potatoes and corn about 300 pounds, barley about 400 and clover frequently over 600 pounds. From this it will be seen that the Maine farmer is wise because he is discounting the season, when he sows oats the year after potatoes in his rotation of clover (two years), potatoes, oats; thus a light water consumer is placed between two heavy consumers. This is important since water is generally the factor which controls the yield of crops. At Rothamsted, England, where wheat has been grown for 60 years on the same piece of land without manure or fertilizer, the average yield per acre is about 121⁄2 bushels, while on land in a rotation—but otherwise similarly treated—the average yield was about 26 bushels. During the last 52 years the total yield of wheat is 665 bushels, which at 75 cents per pushel is worth $498.75. That of continuous barley growing, also without manure or fertilizer, during the same time, was 868 bushels worth $434 at 50 cents a bushel. When wheat and barley were grown in rotation with roots and clover or beans, without manure or fertilizers, the yields and values of the 13 crops of each were roots 9.5 tons, $19; barley 333 bushels, $166.50; clover (5 crops) 4.42 tons, $44.20; beans (8 crops) 104 bushels, $104; wheat, 335 bushels, $251.25; a total of $594.95.
The income from the land under this system is in favor of the rotation. It is $96.20 or 19 per cent, ahead of continuous wheat farming and $150.95 or 34.75 per cent, ahead of continuous barley farming.
Scientists have been kept busy explaining why we should get better yields from a rotation of crops. De Candolle over 100 years ago suggested that plants excreted a poisonous substance which rendered the soil objectionable to others of the same species, a theory which is again coming into some prominence. The continuous culture of wheat and barley at Rothamsted was undertaken partly to test this. Experiments now being conducted at Woburn Fruit Station, England, show that grass injures fruit trees, and it is claimed that the injury seems to be due to some poisonous substance, either direct or due to bacteria. Liebig suggested that plants tended to exhaust the soil by the removal of different ingredients and that as some plants took more of one ingredient than others, a rotation tended to strike a balance. The actual amount of plant food removed from the soil by crops is infinitesimal, and usually a good rotation will remove more than single cropping. The losses of valuable ingredients from the soil by wind or washing are of more importance than those lost by the sale of crops.
The practical benefits from a rotation of crops are now recognized to be manifold, including greater ease in maintaining the soil in proper physical condition; greater opportunity for catching and retaining the water which falls upon the soil, and more economical use of it. Insects and diseases are more easily combatted, and increased vigor of the plants results in increased yield. In addition, labor, manures and fertilizers are more economically used with benefit to the farmer, farm and the nation.