266 POWER OF THE SOIL TO ABSORB SALTS [chap. 



though the effect of the aeration and disturbance of 

 the soil in filling the tanks is still visible in a rather 

 high rate of nitrification. Each tank carried the crop 

 indicated in the first column. 



The rainfall of the year in question, March 1896 to 

 March 1897, amounted to 28-8 inches, most of which 

 fell in the autumn. The most noteworthy results are 

 the effect of the various crops in diminishing the loss 

 of nitrates, which is not wholly to be attributed to the 

 quantity taken up by the crop, because the sum of the 

 nitrogen removed in the crop and that carried off in 

 the drainage water is never equal to the nitrogen 

 removed from the uncropped plots by the drainage 

 water alone. During the comparatively 6Vy spring 

 months the crops leave so little moisture in the soil that 

 nitrification is checked, and the total production of 

 nitrates is less where there is a crop than on the moister 

 uncropped plots. 



When the wheat was followed by a crop of vetches 

 the loss of nitrates during the comparatively wet autumn 

 was considerably reduced. Lastly, the hoeing of the 

 fallow plots resulted in a considerably increased produc- 

 tion of nitrates. 



Time of Application of Manures. 



The facts set out above as to the retention of most 

 of the soluble constituents of manures by the soil, while 

 the nitrates are liable to wash out, have an impor- 

 tant bearing on the season at which artificial manures 

 should be sown. In the first place it is evident that 

 there is no danger of losing phosphates, or even of 

 their washing deep into the soil, when employed in 

 their most soluble form as superphosphate. It is the 

 general custom to sow superphosphate with the drill 

 for roots at the same time as the seed : the large 



