viii.] TIME OF APPLICATION OF MANURES 229 



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 

 quantity of manure near the seedling in its early critical 

 stages is probably valuable, and as the roots of swedes 

 and turnips do not extend very deeply, the phosphoric 

 acid may be placed in the most likely place to reach 

 them. 



But for more deeply rooting crops, hops and fruit 

 or even mangolds, it seems probable that superphos- 

 phate is often applied rather too late in the season, 

 and that if used as a winter instead of a spring dressing 

 it would have a better chance of getting well diffused 

 through the soil. Basic slag and other insoluble phos- 

 phates should be used in the winter or even the autumn : 

 there is no risk of loss, and as much rain as possible 

 is wanted to get them distributed in the soil. As 

 regards potash salts, Dyer's experiments go to show 

 that they descend further in the soil, and are a little 



