CEOP RESIDUES. 61 



having a longer time to collect the scanty supply of food 

 which the soil contains. In hot seasons, with an early 

 harvest, only soils well supplied with food can produce 

 full crops. 



The character of the winter has a considerable influ- 

 ence on that of the following season. In a wet winter 

 the soil may lose nitrates by drainage to a large extent. 

 Root development will also be prevented by excessive 

 wet. After such a winter the wheat crop generally is in 

 a backward condition, and finds itself in an impoverished 

 soil. In climates having a very severe winter the nitrates 

 are preserved from loss by the frozen condition of the 

 soil. In sprin^ the melted snow is removed mostly by 

 surface drainage, the soil beneath being still frozen ; the 

 water produced by the snow consequently does not remove 

 the soluble matter of the soil. 



Crop Residues. The portion of the crop left in the 

 soil after harvest serves most important functions ; on 

 this residue (apart from actual applications of organic 

 manure) the maintenance of the humus, and consequently 

 of the nitrogen of the soil, depends. The quantity of 

 residue left by different crops is very different. From a 

 crop of turnips, mangels, or potatos, practically no root 

 residue remains in the soil ; the residue, in the case of 

 root crops, is limited to the leaves which may remain un- 

 eaten by the stock. The residue of roots and stubble left 

 by an annual cereal crop is rather considerable, but poor 

 in nitrogen. The residues from deeply-rooted crops, 

 which have long held possession of the soil, as sainfoin 

 and red clover, but especially lucerne, are very large, 

 amounting to many tons of dry matter, and containing 



