268 



SOILS AND MANUKES 



nitrogenous manures produce similar exhaustive effects 

 in proportion to the rapidity and potency of their action. 

 In fact, any special manure containing only one fer- 

 tilising ingredient, e.g., superphosphate, kainite, when 

 applied alone, must be more or less exhaustive if it has 

 any effect at all. If an increase of the crop is produced 

 by the action of such a manure, a larger amount of 

 other plant foods will be abstracted from the soil, and 

 the residue will be proportionally diminished. This fact 

 has been demonstrated by experiment. 



RESIDUAL (EXHAUSTIVE) EFFECTS OF NITRATE OF SODA. YIELD OF 

 HAY IN EACH OF THREE YEARS FROM PLOTS WHICH HAD BEEN 

 MANURED WITH NITRATE OF SODA DURING THE FOUR PREVIOUS 

 YEARS. 



PER ACRE. 



Nitrate of soda is not a " lasting " manure. It comes 

 into action very rapidly, and if any escape absorption 

 by the plants it will not remain in the soil, but will .be 

 washed out in the drainage water. Still, a larger pro- 

 portion of the nitrogen in nitrate of soda is recovered in 

 the crops than in the case of any other manure, and it is all 

 recovered in the first year. In some manures, a smaller 

 proportion of the whole is ultimately recovered, and the 

 process occupies some five or ten or twenty years or 

 more. On grass land, the effects of nitrate of soda are 

 not so transient as is sometimes supposed. The effects of 



