102 



SOILS AND MANUEES 



quantities of nitrogenous manures are of course greater, 

 and may amount to from 40 to 50 Ibs. of nitrogen per acre. 

 The first-mentioned quantity is about the same as is con- 

 tained in the single ammonium salts, or nearly as much as 

 is removed from the soil by an average cereal or grass crop. 

 Plot 15, to which the ammonium salts are applied in the 

 autumn, loses more nitrogen than any of the others. 



It should be kept in mind that all the plots were cropped. 

 The losses are therefore much less than from bare soils 

 because plants take iip the nitrates and reduce percolation. 

 Of course no manure would be applied to bare, i.e., fallow 

 land. The amount of nitrates in the drainage water which 

 passes through the bare soil of the gauges (p. 67) is deter- 

 mined periodically. The average monthly results are as 

 follows : 



EAINFALL, DRAINAGE AND NITROGEN, AS NITRIC ACID, IN SAME, 

 FROM BARE SOIL 20-INCH GAUGE. 



AVERAGE FOR 26 YEARS, 18781903. 



Mean. 



