BEHAVIOUR IN THE SOIL 19 



provided with drain-pipes at no great distance beneath the 

 surface, and rain falls frequently after the application of the 

 salt, the composition of the successive discharges of the drain- 

 pipes will be found to vary in a striking manner, following 

 the course of change of the ammonia salt in the soil. If 

 rain falls immediately after the application of the ammonia 

 salt the first discharge of the drain-pipe may contain a little 

 ammonia, the action of the carbonate of lime in the soil 

 being not yet completed. For a few days after the applica- 

 tion of the ammonia salt the drainage water will be found 

 to contain much sulphate of lime, but only a small pro- 

 portion of nitrate. The ammonia is then fixed in the soil, 

 while the acid, w r ith which it was originally combined, has 

 become united with lime. In still later discharges of the 

 pipes the sulphate of lime gradually diminishes, while the 

 proportion of nitrate of lime rapidly increases. Nitrification 

 of the ammonia held by the soil is now in active progress, and 

 fresh quantities of the carbonate of lime in the soil are being 

 brought into solution, combining in the first instance with the 

 nitrous acid arising from the oxidation of the ammonia, the 

 nitrite of lime being afterwards changed by further oxidation 

 into nitrate. 



The analyses of the drainage waters from the plots of the 

 experimental wheat field at Rothamsted afford excellent illus- 

 trations of the statements we have just made. Each plot in 

 this field has a drain-pipe laid beneath it, at a distance of 

 about 2 feet from the surface. The drain-pipe under plot 15 

 had run on October loth, 1880; the water was collected, and 

 the amount of nitrates and chlorides which it contained was 

 determined. On October 25th, ammonia salts, at the rate of 

 400 Ibs. per acre, were spread broadcast on the land, and then 

 ploughed in. The ammonia salts were a mixture of 200 Ibs. 

 of sulphate and 200 Ibs. of chloride of ammonium. Heavy 

 rain occurred on the night of the 26th, and the drain-pipe 

 under the plot was found running on the following morning. 

 Further rain produced a discharge of drainage water on the 

 28th and the 2gth. The pipe did not run again till November 

 1 5th. The amount of chlorine, and of nitrogen as ammonia 



