VIII.] LOSSES TO SOIL IN DRAINAGE WATERS 265 



the summer drainage water of 1879; the figures are, 

 however, exaggerated by the fact that half the nitrate 

 plot received no mineral manures, and therefore grew 

 but a scanty crop. The losses during the winter months 

 are more nearly the same for all plots, and represent to 

 a large degree the nitrification of the organic residues in 

 the soil. The losses from the plots receiving minerals 

 and varying amounts of ammonium salts (5, 6, and 7) 

 increase with each application of nitrogen : the losses 

 from the plots receiving ammonia and various mineral 

 manures diminish as the mineral manure becomes a 

 more complete plant food, because the greater growth of 

 crop thus secured more completely removes the nitrates 

 as they are formed, besides hindering nitrification by 

 drying the surface soil. 



The effect on nitrification of crop and surface 

 cultivation is well seen in the following table of results 



obtained by Deherain, who collected the drainage from 

 cement tanks 2 m. cube and systematically filled with 

 soil taken from corresponding depths in the field. The 

 soils had been several years in the tanks, so that they 

 had settled down into practically normal conditions, 



