viii.] ROTHAMSTED DRAINAGE WATERS 261 



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 1 3 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 

 of water, the unmanured plot will lose about 220 lbs. 

 per acre per annum of lime : equivalent to about 400 lbs. 

 of carbonate of lime, whereas the analysis of the soil 

 shows (p. 252) an annual loss of about 800 lbs. per acre. 

 The discrepancy between these two figures is due to the 

 fact that the results are calculated from but a small 

 number of analyses of the drainage water, the amount 

 of which is also very uncertain. When 400 lbs. of 

 ammonium salts are used as manure, either alone or 

 with minerals, the increased loss of lime calculated on 

 the same basis amounts to 126 lbs. or 225 lbs. of 

 carbonate of lime per acre per annum, as against about 

 240 lbs. found from the analysis of the soil. 



The amount of magnesia lost is small, 5 to 20 lbs. 

 per acre per annum, nor is the amount reaching the 

 drainage water much increased by its application as 

 manure to plots 5, 6, 7, 9, and 14. 



