NITKATES IN THE SOIL 



225 



nitrates. Such a break in composition is not seen in the 

 samples drawn from other fields which are not tile-drained. 



The character of the manuring applied to the surface soil is 

 well seen in the amount of nitrates in the subsoil ; for example, 

 Plots 5, 6, 7, 8 form a series, all getting the same mineral 

 manure, but Plot 5 has no nitrogen, while Plots 6, 7, and 8 

 receive successive increments of ammonium-salts. Down to 

 the depth of 9 feet the samples contain nitrogen as nitrate in 

 approximately the same proportions as it is applied to the 

 surface in the form of ammonium-salts. Again, the total 

 amount of nitrogen as nitrate contained in the whole depth 

 below Plots 6, 7, and 8, as compared with that present below 

 Plot 5 receiving no nitrogen, is much the same as the quantity 

 of nitrogen applied as manure less the amount removed in 

 the crop of 1893. 



TABLE LXXIX. Nitrogen, lb. per acre, 1893. 



* 72 inches only. 



Thus we have evidence that practically the whole of the 

 nitrogen supplied as ammonium-salts is nitrified during the 

 season of growth of the wheat, and whatever is not removed 

 by the plant gets washed down as nitrate into the subsoil, and 

 may be either intercepted by the tile drainage, if any, or find 

 its way into the general stock of underground water. Just in 

 the same way the nitrate supplied to Plot 16 in excess of the 

 requirements of the plant gets also washed down to a consider- 

 able depth in the subsoil. 



The large quantity of deep-seated nitrate shown in the 



analyses is no longer available for crops on the Kothamsted 



p 



