Effect on Succeeding Crops 261 



this drying action of the cover-crop may seriously inter- 

 fere with the germination of the winter grain. On the 

 other hand, it has been demonstrated by Schultz that 

 deep-rooting legumes like lupins may protect the suc- 

 ceeding potato crop from drought. This is accomplished 

 by the lupin roots which, by penetrating into the sub- 

 soil and later decaying, furnish channels along which 

 the potato roots pass downward and possess themselves 

 of the subsoil moisture which would, otherwise, remain 

 inaccessible to them. 



When nitrogen is the controlling factor of growth, the 

 leguminous cover-crops may further affect the siicceed- 

 ing non-legumes by offering to them greater or slighter 

 amounts of this constituent. A case in point is the ex- 

 perience of Schultz, who succeeded, in the course of from 

 twenty-five to thirty years, in increasing the nitrogen 

 content of some of his soil from 0.02 to 0.03 per cent 

 to 0.17 per cent. This is an increase equivalent to about 

 five thousand pounds of nitrogen per acre, when only 

 the surface soil is considered. The nitrogen store of 

 the soil was augmented by him almost entirely at the 

 expense of the atmosphere, for it has been his practice 

 to buy only lime, phosphoric acid and potash, and 

 scarcely any nitrogen at all. 



In so far as the quality of succeeding crops is con- 

 cerned, leguminous green-manures undoubtedly play 

 an essential part. We have reason to believe that such 

 cover-crops grown in orchards affect the keeping quality 

 of the fruit. Much depends, in this case, on the activities 

 of the soil bacteria, since intense decomposition of the 

 green-manure and the formation of large amounts of 



