230 POWER OF THE SOIL TO ABSORB SALTS [chap. 



more subject to washing than the soluble phosphates : 

 for this reason, where sulphate of potash is employed, 

 as for potatoes, it will best be sown with the seed. 

 Where kainit is used, it is best employed as a winter 

 or autumn dressing ; there will be little loss of potash, 

 for this will get fixed chiefly in the surface soil. But 

 the chlorides, which are present in kainit and are 

 sometimes not wholly beneficial in their action upon the 

 crop, will be removed and washed out into the drains or 

 the subsoil water by the winter rains : the magnesia 

 salts also will be precipitated within the soil, and to a 

 large extent removed from possible action upon the 

 crop. Turning to the nitrogen compounds, it is 

 necessary to keep in mind that all of them will become 

 transformed into nitrates which are liable to be washed 

 out All insoluble organic manures should be put 

 on before or during the winter : the decay processes 

 will begin, resulting in the formation of amino-acids, 

 ammonia, etc., which will become fixed in the soil, but 

 the low winter temperatures will not permit of much 

 nitrification. Liquid manure and similar materials 

 containing such readily nitrifiable substances as urea 

 and ammonium carbonate, should be reserved until 

 early spring, so that the crop may be growing whenever 

 nitrification begins. Ammonium salts are very rapidly 

 nitrified, so that they should only be used in spring. 

 At Rothamsted nitrates begin to appear in the drainage 

 water immediately after the application of the ammonium 

 salts to the wheat plots in March if rain falls, and one 

 of the plots which has its ammonium salts applied in 

 autumn shows not only a considerable falling off in 

 crop but also large quantities of nitrates in the winter 

 drainage waters. 



The following table shows the amounts of nitrates 

 removed in the drainage water from the two plots which 



