ROTATION 27 



to note the influence of each crop upon the moisture 

 content of the soil (see p. 50); thus, rye removes less 

 moisture from the soil than wheat. Oats draw heav- 

 il}' upon the moisture content. 



The potato crop is not usually considered to be a 

 heaVy water consumer. It leaves the soil in a rela- 

 tively moist condition; hence, the wisdom of the Maine 

 four-year course, in which oats succeed potatoes. 

 This course requires but one deep plowing in four 

 years, that for the potatoes, and in this it is econom- 

 ical. Peas use a relatively small amount of water, 

 and would leave the soil in good shape for potatoes. 

 In Wisconsin,' while potatoes grown in rotation yield- 

 ed 342.8 bushels per acre, a crop grown on an old 

 alfalfa sod yielded but 277.7 bushels per acre, al- 

 though the rainfall was considered adequate to pro- 

 duce a full crop. In some cases clover tends to 

 leave the soil drier than some other crops, and its 

 use as the preceding crop for potatoes ma}^ be detri- 

 mental. In most cases, however, a leguminous crop 

 is the best to precede potatoes. In Florida" cow-peas 

 preceding potatoes increased the yield 40 per cent. 

 The Ohio Station^ found that in the three-course rota- 

 tion — potatoes, wheat, clover — whenever good crops of 

 clover were grown the economy of using nitrogenous 

 fertilizers for the potatoes was questionable, thus show- 

 ing that a good rotation is equivalent to manuring. 

 Plowing under a leguminous crop is held to be good 

 practice on farms where an adequate supply of manure 

 is not forthcoming and little stock is kept; thus, a-t the 



' wis. Report, 1902, p. 188. * Fla. Report, 1900-1901, p. 28. 



' Ohio Bui. 125, p. 132. 



