2/6 SOILS AND FERTILIZERS 



weak feeding crop should be followed by a strong 

 feeding crop, and then each is properly supplied with 

 food. It would be poor economy, on an average 

 soil, to follow clover and timothy with mangels, then 

 with barley, and finally with flax, because the flax 

 would be placed at a serious disadvantage following two 

 strong feeding crops. If reversed, the crops would 

 be placed in order of assimilative power, and the 

 best use would be made of the sod-crop residue. 

 When crops of dissimilar feeding habits follow each 

 other, not only are the crop residues used to the best 

 advantage, but the soil is relieved of excessive demands 

 on special elements. For example, wheat and clover 

 take different amounts of potash and lime from the 

 soil. Wheat has the power of feeding upon silicates 

 of potash which clover cannot assimilate, hence wheat 

 and clover in rotation relieve the soil of excessive 

 demands on the potash. 



333. Nitrogen-consuming and Nitrogen-producing Crops. 



It is possible in a five-course rotation to maintain or 

 even increase the nitrogen of the soil without the use 

 of nitrogenous manures. In Section 145 an example 

 is given of a rotation which has left the soil with a 

 better supply of nitrogen than at the beginning. 

 When a soil produces a good clover crop once in 

 five years, and stable manure is used once during 

 that time, the soil nitrogen is not decreased. Not only 

 is nitrification influenced by cultivation and crop rota- 



