156 MANURE. 



that their stability is greater or less. Nitrates are less stable 

 compounds than sulphates, sulphates less stable than chlo- 

 rides, or muriates, and these last less stable than carbonates. 

 Hence, the ease with which the nitrogen of a salt is yielded, 

 affects the result. Time, then, is required to produce froin 

 equal amounts of nitrogen, equal effects from different salts 

 containing that element. 



This is true, also, of organic, nitrogenous manures. The 

 nitrogen is effective in proportion to the rapidity of decay. 

 Hence, the nitrogen in horns, hair, feathers, hoofs, leather- 

 shavings, woollen rags and flocks, produces not the saiire 

 effects in the same time, with an equal amount of nitrogen 

 in flesh and blood. Nitrogen in soil may be useless from 

 its state of combination. 



It has been proved by Krocker that rocks, and even bar- 

 ren soils, at the usual depth of tillage, contain an amount of 

 ammonia exceeding per acre that of any fair crop, raised by 

 the aid of best farm-yard manure, on an acre of the best soil. 

 It is not enough that tons and tons of ammonia are already 

 existent in soil, if that ammonia can be extracted only by 

 chemical processes, and human manipulation. No matter 

 how much of this element may be in rain, how much may 

 exist in the soil, aided by the inorganic salts, fair average 

 crops may be raised by these natural sources of ammonia. 

 To obtain truly profitable crops, an excess beyond the na- 

 tural supply is absolutely essential. To keep up this excess, 

 and to obtain the largest returns for the seed sown, nitrogen 

 in the shape of salts, or of readily decomposing organic mat- 

 ter, must be supplied with inorganic salts. The nitrogenous 

 principle gives at once an energy to vegetation, enabling it 

 to unfold early and largely those organs, the roots and leaves, 

 by which the earth and air contribute their portion to the 

 growth of plants. 



