EXPERIMENTS ON CLOVER-SOILS. 159 



nitrogen is assimilated, par excellence by cereal crops,and in which, 

 at all events, it is more efficacious than in any other state of com- 

 bination wherein it may be used as a fertilizer. 



" When the clover-lay is plowed up early, the decay of the clover 

 is sufficiently advanced by the time the young wheat-plant stands 

 in need of readily available nitrogenous food, and this being uni- 

 formly distributed through the whole of the cultivated soil, is 

 ready to benefit every single plant. This equal and abundant dis- 

 tribution of food, peculiarly valuable to cereals, is a great advan- 

 tage, and speaks strongly in favor of clover as a preparatory crop 

 for wheat. 



" Nitrate of soda, an excellent spring top-dressing for wheat and 

 cereals in general, in some seasons fails to produce as good an effect 

 as in others. In very dry springs, the rainfall is not sufficient to 

 wash it properly into the soil and to distribute it equally, and in 

 very wet seasons it is apt to be washed either into the drains or 

 into a stratum of the soil not accessible to the roots of the young 

 wheat. As, therefore, the character of the approaching season 

 can not usually be predicted, the application of nitrate of soda to 

 wheat is always attended with more or less uncertainty. 



" The case is different, when a good crop of clover-hay has been 

 obtained from the land on which wheat is intended to be grown 

 afterwards. An enormous quantity of nitrogenous organic matter, 

 as we have seen, is left in the land after the removal of the clover- 

 crop ; and these remains gradually decay and furnish ammonia, 

 which at first and during the colder months of the year, is retained 

 by the well known absorbing properties which all good wheat- 

 soils possess. In spring, when warmer weather sets in, and the 

 wheat begins to make a push, these ammonia compounds in the soil 

 are by degrees oxidized into nitrates ; and as this change into food 

 peculiarly favorable to young cereal plants, proceeds slowly 

 but steadily, we have in the soil itself, after clover, a source from 

 which nitrates are continuously produced ; so that it does not much 

 affect the final yield of wheat, whether heavy rains remove some 

 or all of the nitrate present in the soil. The clover remains thus 

 afford a more continuous source from which nitrates are produced, 

 and greater certainty for a good crop of wheat than, when recourse 

 is had to nitrogenous top-dressings in the spring. 



SUMMARY. 



" The following are some of the chief points of interest which I 

 have endeavored fully to develope in the preceding pages : 

 " 1. A good crop of clover removes from the soil more potash, 



