LOSS OF NITKATES BY DRAINAGE 



235 



spring, as is now more generally the case, the losses of nitrates 

 are very much reduced ; not only is the temperature of the soil 

 lower, so that nitrification takes place more slowly, but the 

 growing crop both diminishes the percolation and takes up the 

 nitrates as fast as they are produced. The figures, however, 

 for Plot 7 and Plot 9, Table LXXXIL, show some rise in the 

 concentration of the drainage water in the early spring, follow- 

 ing the application of manure. 



By combining the figures obtained for the concentration of 

 the water flowing from the Broadbalk field drains with the 

 amounts of water percolating through the drain-gauge con- 

 taining 60 inches of bare soil (see p. 22), an estimate can 



TABLE LXXXV. Nitric Nitrogen in Drainage Water. Lb. per acre. 



be formed of the losses to the land by drainage under each 

 system of manuring, an estimate rendered erroneous because 

 it does not take into account the drying effect of the crop. 

 However, the figures thus obtained, though imperfect, are 

 instructive, and are set out in Table LXXXV. for two years, 

 each divided into two periods : first, from the date of sowing 

 the nitrogenous manures up to harvest ; secondly, from harvest 

 round again to the so wing of the manures in spring. 



The seasons were rather exceptional, the summer rainfall 



