26 



any crop may be made to some extent a means of soil improvement ; 

 but only by the culture of plants belonging to the clover family can the 

 store of nitrogen in the soil be increased. 



The catch-crop is in many cases highly useful as a cover in winter, to 

 protect the soil from loss of line particles by wind or from washing. 

 For this purpose we must have crops hardy in winter. It is, of course, 

 self-evident that other crops besides winter annuals often have a value 

 as catch-crops. 



AbilUy to stand frosts is in a very great many cases a highly impor- 

 tant characteristic of the catch-crop. It is often sown after the main 

 crop. The time before the probable coming of frosts is short. Only a 

 crop which will continue its growth in spite of frosts Avill prove of much 

 value. Further, it is in late fall that the soluble nitrogen compomids 

 are liable to be washed out of the soil by heavy rains unless the soil is 

 filled with the feeding rootlets of growing plants. Only crops which 

 resist frost can prevent this loss. 



The catch-crop is grown sometimes chiefly because of its value as a 

 money crop. This, however, in ordinary farming will seldom be the 

 case. It is much more often grown as a means of augmenting the sup- 

 ply of food for the stock of the farm. In other cases, though less fre- 

 quently, soil improvement by green manuring is the principal object in 

 view in its culture. 



It is possible by judicious selection of crops to realize both of the last- 

 named objects at the same time to a very considerable extent. Sound 

 New England dogma has it, " You can't eat your cake and have it too." 

 In the matter of nitrogen this old saying is disproved. You may grow a 

 crop of clover or clover-like plants; you (or yoiu- cow if you prefer) 

 may eat this crop, and by so doing consume an enormous quantity of 

 nitrogen ; and yet in the soil upon which the crop was grown will be 

 found more nitrogen than was contained in that soil at the outset. Is 

 not this " eating one's cake and having it too " ? It is those crops which 

 enable us to do this which are among the most valuable as catch-crops. 



Of the importance and value of money or of fodder crops it is unnec- 

 essary to write; but concerning the possible benefits of green-manur- 

 ing a few words may be useful. 



Possible Benefits of Green-manuking. 

 Amonglthe possible and probable eff'ects of green-manuring its relation 

 to the supply of plant food in soil is one of the most important. Of the 

 important elements derived from the soil which contribute to the nour- 

 ishment of plants nitrogen is the only one the amount of which can be 

 increased by green-manuring. This may be increased by the cultiva- 

 tion under suitable conditions of legumes (plants belonging to the clover, 

 pea and bean family). These plants, as has been so many times pointed 

 out in recent years, have the capacity to take nitrogen from the atmos- 

 phere ; and if these plants be ploughed in or allowed to decay upon the 

 soil, the nitrogen which they have taken from the air becomes available 

 to plants belonging to other families which themselves have not the 

 power to draw upon the air for this element. 



