EXTENSION COUESE IN SOILS. 87 



On heavier soils, where grain and stock raising is practiced, a 

 longer rotation is usually desirable, especially if some of the culti- 

 vated land is also to be used for pasture. A 6-year rotation can 

 then be worked out, such as the following: Corn, wheat, oats, clover, 

 timothy, and pasture, or it can be shortened to five years by omitting 

 either one of the grains or the pasture year. 



Rotation for different types of soil on tTie same farm. — Over a con- 

 siderable part of the United States there is such a variation in soils 

 within short distances that the relation of one type of soil to the 

 other must be fully considered. When a farm includes sand and 

 marsh soils which have been drained and brought under cultivation, 

 all of the manure should be used on the sandy soil, since the marsh 

 soil does not need nitrogen, and can be kept in a high state of fertility 

 through the use of moderate quantities of commercial fertilizers con- 

 taining potassium and phosphorus, thereby making it possible to 

 keep the fertility of the whole farm in a high state. The same 

 method may be used when the farm includes clay and marsh soils. 

 In such cases it may be necessary to develop two or more systems of 

 rotations on a single farm. All of these matters must of course be 

 worked out with reference to each particular case, and the success 

 of the farmer depends to a considerable extent on his judgment in 

 working out logical systems of cropping adapted to his soil conditions 

 as well as to his market and other factors affecting his work. 



Rotation systems for permanent fertility (Ref. No. 5, Chaps. XV and 

 XVI, pp. 226-235). — ^After all, it must be recognized that the most 

 important problem in any system of farming is so to conduct the 

 cropping and the disposition of the crops that the fertility of the 

 soil shall not alone be maintained, but that it shall be constantly 

 built up in the best and most profitable manner. Herein lies one of 

 the most vital parts of good farm management. The somewhat 

 prevalent idea among farmers that simply rotating crops will improve, 

 or even maintain, the fertility of soil is without a safe foundation. 

 It is true, for reasons stated in the beginning of this lesson, that far 

 better results in cropping will be realized from a well-planned rotation 

 than from a single-crop system. But actually to build up the 

 fertility of a soil one should first understand what elements of plant 

 food are low in the soil, then the cropping system, the type of farming, 

 the building up of humus and mineral elements through manures 

 and fertilizers, and the physical management of the soil should all be 

 so studied and planned that gradual soil improvement wiU result. 

 The management necessary to attain this end wiU vary, of course, 

 with the system of farming practiced. 



In vegetable gardening, manure from cities can usually be secured 

 in quantity, and the soil can be improved while profits are realized 

 from the crops by the purchase of both stable manure and com- 



