298 DRY-FARMING 
The persistent application of the proper cultural 
methods of dry-farming will set free the most im- 
portant plant-foods, and on well-cultivated farms 
nitrogen is the only element likely to be absent in 
serious amounts. 
The rotation of crops on dry-farms is usually 
advocated in districts like the Great Plains area, 
where the annual rainfall is over fifteen inches and 
the major part of the precipitation comes in spring 
and summer. The various rotations ordinarily 
include one or more crops of small grains, a hoed 
crop like corn or potatoes, a leguminous crop, and 
sometimes a fallow year. The leguminous crop is 
grown to secure a fresh supply of nitrogen; the hoed 
crop, to enable the air and sunshine to act thoroughly 
oh the soil grains and to liberate plant-food, such as 
potash and phosphoric acid; and the grain crops to 
take up plant-food not reached by the root systems 
of the other plants. The subject of proper rotation 
of crops has always been a difficult one, and very 
little information exists on it as practiced on dry- 
farms. Chilcott has done considerable work on 
rotations in the Great Plains district, but he frankly 
admits that many years of trial will be necessary for 
the elucidation of trustworthy principles. Some of 
the best rotations found by Chilcott up to the present 
are: — 
Corn — Wheat — Oats 
Barley — Oats — Corn 
Fallow — Wheat — Oats 
