224 POWER OF THE SOIL TO ABSORB SALTS |chap. 



An examination of these figures shows that the 

 amount of organic matter and ammonia reaching the 

 drains is practically nil; the organic matter supplied 

 as dung, and the ammonia, which is employed up to 

 400 lbs. of mixed ammonium chloride and sulphate per 

 acre, are wholly retained by the soil. The effect, how- 

 ever, of adding either organic compounds of nitrogen or 

 ammonium salts is to increase the proportion of nitrates 

 in the drainage water. Lime is the chief constituent of 

 the dissolved matter in the drainage waters, the propor- 

 tion is lowest for the unmanured plot (3), it rises with 

 the application of minerals (5), and rises again with each 

 successive application of ammonium salts (6) and (7). The 

 formation of calcium chloride and sulphate respectively, 

 when the corresponding ammonium salts are applied to 

 land containing calcium carbonate, has already been 

 discussed : it is well seen in the increased richness in 

 lime, sulphuric acid, and chlorine of the drainage water 

 from 6 and 7, which receive 200 and 400 lbs. respectively 

 of ammonium salts, as compared with 5, which receives 

 the same minerals without any nitrogen compounds. Plot 

 1 1 receives superphosphate in addition to the ammonium 

 salts which 10 receives: the effect of the gypsum con- 

 tained in the superphosphate is seen in the increased 

 lime and sulphuric acid content of the drainage water of 

 1 1. The increase is not so great, however, as that caused 

 by the addition of sulphates of potash and magnesia to 

 the superphosphate and ammonium salts (plots 13 and 14) 

 whereas sulphate of soda causes little loss of lime (12). 

 The use of nitrate of soda on plot 9 causes no increase 

 in the proportion of lime in the drainage water, but a 

 large quantity is removed, chiefly as sulphate, from plot 

 2, receiving dung every year. The quantity of lime 

 removed annually in this way will be very great: 

 assuming a mean annual drainage equal to 10 inches 



