CHAPTER 7. 



ROTATION OF CROPS. 



The aim of rotations. Bare Fallow.— "EEects 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 

 grass, or in leguminous crops — Advantages of green manuring. 

 Distinctive Characteristics of Crops. — Differences in periods of 

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

 food demanded. Losses to the Land during Eotatioji. — Losses in 

 an assumed four-course rotation, how replaced — Losses of nitrates 

 — Gain of nitrogen from the atmosphere — Economy of nitrogen — 

 Use of catch crops — Sale of produce other than corn and meat. 

 Eqtiilihrium in Soils. 



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 Kothamsted experiments show that excellent crops 

 of wheat, barley, and mangel may be continuously 

 obtained if appropriate manures are 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 land for wheat. The soil is repeatedly 



