664 



Notes on Manures. 



[Oct., 



NOTES ON MANURES FOR OCTOBER. 



E. J. KussELL, D.Sc, F.E.S., 



Rothamsted Experimental Station. 



Effect of the Drought on Fertilisers in the Soil. — In a season 

 so exceptional as the one now drawing to a close there hab 

 necessarily been much experience with fertilisers that was wholly 

 unexpected. In many cases land was well manured for roots, 

 but no roots grew; elsewhere much fertiliser has been put on 

 grass land with no effect. The question therefore arises, to what 

 extent can fertiHsers added to the soil in seasons such as the 

 present be relied upon for next year's crops? 



There is abundant evidence to show that Potash and Phosphates 

 remain unchanged during a dry season, and they will therefore 

 come in perfectly well for succeeding crops in the rotation : 

 no loss need be feared. The fertiliser added has not been wasted, 

 but is simply lying where it can be taken up by the plant. This 

 holds true of sulphate of potash, muriate of potash, kainit, super- 

 phosphate, basic slag, mineral phosphates and bone manures. 



Nitrogenous manures, however, are liable to behave differently. 

 Some of them have probably been taken up by the crop, and, if 

 so, they cannot of course be expected to act in the soil again. 

 Cases have come to the writer's notice where a quick- acting 

 nitrate was taken up by the grass crop, as shown by the dark 

 green colour and additional growth of the herbage; while the 

 slower acting nitrolim was not taken up, but lay on the soil 

 unchanged. Nitrogenous manures left thus unabsorbed will 

 probably change rapidly to nitrates w^hen the soil becomes 

 sufficiently wet, and they may then be taken by a crop, or 

 washed out of the soil; but they are not likely to be left 

 unchanged in the soil. So much depends on local conditions 

 that it is difficult to lay down general rules; the following, how- 

 ever, will probably not be far wrong: — 



1 . On grass land intended for hay the nitrogenous manure will 

 probably remain effective for the coming season. It has happened 

 after a great drought that heavy rain was followed by an 

 unusually copious growth of grass. 



