CHAPTER Y. 



ROTATION OP CROPS. 



The aim of rotations. Bare Fallow. Effects on the soil Production of 

 nitrates. Green Crops. Effects of feeding on the land, or ploughing 

 in Gain of nitrogen to the soil by laying down land in pasture, 

 or in leguminous crops Advantages of green manuring. Dis- 

 tinctive characteristics of Crops. Differences in periods of growth, 

 range of roots, powers of assimilation, and quantity of food 

 demanded. Losses to the land during rotation. Losses in an assumed 

 four-course rotation, how replaced Losses of nitrates, how prevent- 

 ed Gain of nitrogen from the atmosphere Economical rotations 

 Sale of produce other than corn and meat. 



IT is by no means impossible to grow the same crop 

 with success year after year on the same land ; ordinary 

 pasture is indeed an example of continuous cropping. 

 The Rothamsted experiments show that excellent crops of 

 wheat, barley, and mangel may be continuously obtained 

 if appropriate manure is annually applied, and the land 

 kept free from weeds. A rotation of crops is resorted to 

 in ordinary practice in consequence of the facilities 

 which such a plan affords for cleaning the land, and from 

 the greater economy of manure which results from this 

 practice. One of the principal aims of a rotation is to 

 bring the land from time to time into a condition suitable 

 for growing cereal crops ; this suitable condition consists 

 mainly in the accumulation of nitrogenous plant food in 

 the surface soil. 



Bare Fallow. A bare fallow is one of the oldest modes 

 of preparing soil for wheat. The soil is ploughed, and 



