IV. 



THE REACTIONS OCCURRING- IN SOILS 



73 



According to later results at Eothamsted, the average for twenty 

 years gives rainfall, 30 in. ; drainage from uncropped land, 14 in. 

 From a soil bearing a vigorous crop the amount of drainage is very 

 much less (not much more than half), especially in summer, when 

 drainage is often entirely suspended, except after very heavy rain. 

 The composition of the drainage water will thus be altered, even if the 

 crop does not actively exert any influence, for the dissolved matter 

 should become more concentrated. But the plant exerts an influence 

 in taking up and retaining much of the dissolved matter in the water, 

 particularly the nitrates. 



The average amount of chlorine in rain-water at Eothamsted is 

 about 2*0 parts per million. In drainage water from 60 in. of 

 bare soil (equal, as is shown in the table just given, to not quite half 

 the rainfall) the average amount is 3'9 parts per -million and is very 

 constant. Nitrogen as nitrates in drainage water from the same soil 

 varied from about 10 in winter to about 14 parts per million in 

 summer, the yearly average being 10' 7, or a loss of about 40 Ib. per 

 acre per annum. From unmanured wheat land, the drainage water 

 contained as the average for the whole year 6O parts per million of 

 chlorine and 3'4 parts per million of nitrogen as nitrates, the latter 

 varying from 4 -3 in winter to O'l in summer. 



In manured (farm-yard) wheat land the average numbers were 7 3 

 for chlorine and 5 '8 for nitrogen. 



From these numbers it appears that at Eothamsted the amount of 

 chlorine in the drainage water is almost exactly equal to that supplied 

 in the rain. From the results of a large number of analyses of 

 drainage water and well waters, Warington concludes that 4 '4 parts of 

 nitrogen as nitrates per million is the average proportion in the 

 drainage from cultivated land in the Eothamsted district. 



