vili.] ROTHAMSTED DRAINAGE WATERS 259 



The drainage from the continuously manured wheat 

 plots at Rothamsted, each of which possesses a tile drain 

 running down the centre at a depth of 2 feet to 2 feet 

 6 inches, has been collected from time to time and com- 

 pletely analysed by Voelcker and Frankland ; in addition, 

 systematic determinations of the nitrogen contents have 

 been made for many years. In a general way, the chief 

 constituent of the various drainage waters is lime, either 

 as bicarbonate, sulphate, chloride, or nitrate ; soda is 

 the only other base present in any quantity, very small 

 amounts of magnesia, potash, and ammonia pass into 

 the drains. Of the acid radicles, chlorine and sulphuric 

 acid predominate, according to the manuring, and the 

 proportion of phosphoric acid is minute ; but the amount 

 of nitric acid varies according to the manure applied 

 and the season at which the water is collected. 



The table on p. 260 shows the complete analysis of 

 the drainage water from twelve of the plots. 



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 



