THE WATER IN A SOIL. 75 



Drainage Nitrogen as 



Case. Crop in Ib. per acre. in nitrates in 



inches. Ib. per acre. 



1 Fallow, not dug ... ... 11-11 186-7 



2 Eye grass, 4754ft. ... ... 7'80 2-3 



3 Oats, 1741ft., and straw, 4036ft. ... 7*29 7-4 



4 ,, 1634ft., ,, 37941b. ... 7'92 12-7 



5 ,, 1634ft., 3794ft. ... 8-04 23-4 



6 Maize, green fodder, 62,500ft. ... 6'93 21-6 



7 63,616ft. ... 6-66 14-7 



8 ,, ,, 66,964ft. ... 6-58 25-6 



9 Wheat and vetches (wheat 1853ft., 



straw 3794ft., vetches 6696ft.) ... 6*62 12-8 



10 Wheat only (wheat 1803ft., straw 



3817ft.) ... ... ... 7-49 29-7 



11 Wheat and vetches (wheat 1429ft., 



straw 3794ft., vetches 5803ft.) ... 6-86 7-1 



12 Fallow, dug ... ... ... 11-54 196-4 



13 not dug 11-15 157-9 



14 ,, dug and rolled ... ... 11-23 183-2 



15 Potatoes, tubers, 24,553ft. ... 5-83 24-7 



16 Vines, grapes, 16,786ft. ... ... 7'45 36-4 



17 ,, 16,920ft. ... ... 7-41 75-0 



18 Sugar beet, roots, 25,000ft. ... 7'17 2-4 



19 ,; ,, 29,241ft. ... 7-17 0-3 



20 ,, ,, 27,902ft. ... 7-64 0-3 



The effect of vegetation in checking the loss of nitrates is 

 clearly evident in these results. This it does in several ways : 

 (i.) By actually absorbing the nitrates ; (ii.) by lessening the 

 amount of drainage by increasing the evaporation ; and (iii.) in 

 checking nitrification by rendering the soil too dry. This last 

 effect is most marked when the period of most active growth 

 corresponds with a dry portion of the year and is least evident 

 when rain is abundant during that period. [Compare the 

 results with maize (with late development) the crop of 

 which is estimated to contain 156ft. nitrogen per acre ; this 

 added to 20ft., the amount lost in drainage, gives 176ft. nitro- 

 gen per acre (almost equivalent to that produced on fallow) 

 with those with wheat (case 10), early growth during 



