THE soil treatment prescribed in the precedingchapters rests upon (1) deep and thorough plowing, done preferably in the fall; (2)thorough cultivation to form a mulch over the surface of the land, and (3) cleansummer fallowing every other year under low rainfall or every third or fourth yearunder abundant rainfall.

Students of dry-farming all agree that thoroughcultivation of the topsoil prevents the evaporation of soil-moisture, but some havequestioned the value of deep and fall plowing and the occasional clean summer fallow.It is the purpose of this chapter to state the findings of practical men with referenceto the value of plowing and fallowing in producing large crop yields under dry-farmconditions.

It will be shown in Chapter XVIII that the firstattempts to produce crops without irrigation under a limited rainfall were made independentlyin many diverse places. California, Utah, and the Columbia Basin, as far as can nowbe learned, as well as the Great Plains area, were all independent pioneers in theart of dry-farming. It is a most significant fact that these diverse localities,operating under different conditions as to soil and climate, have developed practicallythe same system of dry-farming. In all these places the best dry-farmers practicedeep plowing wherever the subsoil will permit it; fall plowing wherever the climatewill permit it; the sowing of fall grain wherever the winters will permit it, andthe clean summer fallow every other year, or every third or fourth year. H. W. Campbell,who has been the leading exponent of dry-farming in the Great Plains area, beganhis work without the clean summer fallow as a part of his system, but has long sinceadopted it for that section of the country. It is scarcely to be believed that thesepractices, developed laboriously through a long succession of years in widely separatedlocalities, do not rest upon correct scientific principles. In any case, the accumulatedexperience of the dry-farmers in this country confirms the doctrines of soil tillagefor dry-farms laid down in the preceding chapters.

At the Dry-Farming Congresses large numbers ofpractical farmers assemble for the purpose of exchanging experiences and views. Thereports of the Congress show a great difference of opinion on minor matters and awonderful unanimity of opinion on the more fundamental questions. For instance, deepplowing was recommended by all who touched upon the subject in their remarks; thoughone farmer, who lived in a locality the subsoil of which was very inert, recommendedthat the depth of plowing should be increased gradually until the full depth is reached,to avoid a succession of poor crop years while the lifeless soil was being vivified.The states of Utah, Montana, Wyoming, South Dakota, Colorado, Kansas, Nebraska, andthe provinces of Alberta and Saskatchewan of Canada all specifically declared throughone to eight representatives from each state in favor of deep plowing as a fundamentalpractice in dry-farming. Fall plowing, wherever the climatic conditions make it possible,was similarly advocated by all the speakers. Farmers in certain localities had foundthe soil so dry in the fall that plowing was difficult, but Campbell insisted thateven in such places it would be profitable to use power enough to break up the landbefore the winter season set in. Numerous speakers from the states of Utah, Wyoming,Montana, Nebraska, and a number of the Great Plains states, as well as from the ChineseEmpire, declared themselves as favoring fall plowing. Scareely a dissenting voicewas raised.

In the discussion of the clean summer fallowas a vital principle of dry-farming a slight difference of opinion was discovered.Farmers from some of the localities insisted that the clean summer fallow every otheryear was indispensable; others that one in three years was sufficient; and othersone in four years, and a few doubtful the wisdom of it altogether. However, all thespeakers agreed that clean and thorough cultivation should be practiced faithfullyduring the spring, and fall of the fallow year. The appreciation of the fact thatweeds consume precious moisture and fertility seemed to be general among the dry-farmersfrom all sections of the country. The following states, provinces, and countriesdeclared themselves as being definitely and emphatically in favor of clean summerfallowing:

California, Utah, Nevada, Washington, Montana,Idaho, Colorado, New Mexico, North Dakota, Nebraska, Alberta, Saskatchewan, Russia,Turkey, the Transvaal, Brazil, and Australia. Each of these many districts was representedby one to ten or more representatives. The only state to declare somewhat vigorouslyagainst it was from the Great Plains area, and a warning voice was heard from theUnited States Department of Agriculture. The recorded practical experience of thefarmers over the whole of the dry-farm territory of the United States leads to theconviction that fallowing must he accepted as a practice which resulted in successfuldry-farming. Further, the experimental leaders in the dry-farm movement, whetherworking under private, state, or governmental direction, are, with very few exceptions,strongly in favor of deep fall plowing and clean summer fallowing as parts of thedry-farm system.

The chief reluctance to accept clean summer fallowingas a principle of dry-farming appears chicfly among students of the Great Plainsarea. Even there it is admitted by all that a wheat crop following a fallow yearis larger and better than one following wheat. There seem, however, to be two seriousreasons for objecting to it. First, a fear that a clean summer fallow, practicedevery second, third, or fourth year, will cause a large diminution of the organicmatter in the soil, resulting finally in complete crop failure; and second, a beliefthat a hoed crop, like corn or potatoes, exerts the same beneficial effect.

It is undoubtedly true that the thorough tillageinvolved in dry-farming exposes to the action of the elements the organic matterof the soil and thereby favors rapid oxidation. For that reason the different waysin which organic matter may be supplied regularly to dry-farms are pointed out inChapter XIV. It may also be observed that the header harvesting system employed overa large part of the dry-farm territory leaves the large header stubble to be plowedunder, and it is probable that under such methods more organic matter is added tothe soil during the year of cropping than is lost during the year of fallowing. Itmay, moreover, be observed that thorough tillage of a crop like corn or potatoestends to cause a loss of the organic matter of the soil to a degree nearly as largeas is the case when a fallow field is well cultivated. The thorough stirring of thesoil under an arid or semiarid climate, which is an essential feature of dry-farming,will always result in a decrease in organic matter. It matters little whether thesoil is fallow or in crop during the process of cultivation, so far as the resultis concerned.

A serious matter connected with fallowing inthe Great Plains area is the blowing of the loose well-tilled soil of the fallowfields, which results from the heavy winds that blow so steadily over a large partof the western slope of the Mississippi Valley. This is largely avoided when cropsare grown on the land, even when it is well tilled.

The theory, recently proposed, that in the GreatPlains area, where the rains come chicfly in summer, the growing of hoed crops maytake the place of the summer fallow, is said to be based on experimental data notyet published. Careful and conscientious experimenters, as Chilcott and his co-laborers,indicate in their statements that in many cases the yields of wheat, after a hoedcrop, have been larger than after a fallow year. The doctrine has, therefore, beenrather widely disseminated that fallowing has no place in the dry-farming of theGreat Plains area and should be replaced by the growing of hoed crops. Chilcott,who is the chief exponent of this doctrine, declares, however, that it is only withspring-grown crops and for a succession of normal years that fallowing may be omitted,and that fallowing must be resorted to as a safeguard or temporary expedient to guardagainst total loss of crop where extreme drouth is anticipated; that is, where therainfall falls below the average. He further explains that continuous grain cropping,even with careful plowing and spring and fall tillage, is unsuccessful; but holdsthat certain rotations of crops, including grain and a hoed crop every other year,are often more profitable than grain alternating with clean summer fallow. He furtherbelieves that the fallow year every third or fourth year is sufficient for GreatPlains conditions. Jardine explains that whenever fall grain is grown in the GreatPlains area, the fallow is remarkably helpful, and in fact because of the dry wintersis practically indispensable.

This latter view is confirmed by the experimentalresults obtained by Atkinson and others at the Montana Experiment Stations, whichare conducted under approximately Great Plains conditions.

It should be mentioned also that in Saskatchewan,in the north end of the Great Plains area, and which is characteristic, except fora lower annual temperature, of the whole area, and where dry-farming has been practicedfor a quarter of a century, the clean summer fallow has come to be an establishedpractice.

This recent discussion of the place of fallowingin the agriculture of the Great Plains area illustrates what has been said so oftenin this volume about the adapting of principles to local conditions. Wherever thesummer rainfall is sufficient to mature a crop, fallowing for the purpose of storingmoisture in the soil is unnecessary; the only value of the fallow year under suchconditions would be to set free fertility. In the Great Plains area the rainfallis somewhat higher than elsewhere in the dry-farm territory and most of it comesin summer; and the summer precipitation is probably enough in average years to maturecrops, providing soil conditions are favorable. The main considerations, then, areto keep the soils open for the reception of water and to maintain the soils in asufficiently fertile condition to produce, as explained in Chapter IX, plants witha minimum amount of water. This is accomplished very largely by the year of hoedcrop, when the soil is as well stirred as under a clean fallow.

The dry-farmer must never forget that the criticalelement in dry-farming is water and that the annual rainfall will in the very natureof things vary from year to year, with the result that the dry year, or the yearwith a precipitation below the average, is sure to come. In somewhat wet years themoisture stored in the soil is of comparatively little consequence, but in a yearof drouth it will be the main dependence of the farmer. Now, whether a crop be hoedor not, it requires water for its growth, and land which is continuously croppedeven with a variety of crops is likely to be so largely depleted of its moisturethat, when the year of drouth comes, failure will probably result.

The precariousness of dry-farming must be doneaway with. The year of drouth must be expected every year. Only as certainty of cropyield is assured will dry-farming rise to a respected place by the side of otherbranches of agriculture. To attain such certainty and respect clean summer fallowingevery second, third, or fourth year, according to the average rainfall, is probablyindispensable; and future investigations, long enough continued, will doubtless confirmthis prediction. Undoubtedly, a rotation of crops, including hoed crops, will findan important place in dry-farming, but probably not to the complete exclusion ofthe clean summer fallow.

Jethro Tull, two hundred years ago, discoveredthat thorough tillage of the soil gave crops that in some cases could not be producedby the addition of manure, and he came to the erroneous conclusion that "tillageis manure." In recent days we have learned the value of tillage in conservingmoisture and in enabling plants to reach maturity with the least amount of water,and we may be tempted to believe that "tillage is moisture." This, likeTull's statement, is a fallacy and must be avoided. Tillage can take the place ofmoisture only to a limited degree. Water is the essential consideration in dry-farming,else there would be no dry-farming.