76 THE EEACTIONS OCCURRING IN SOILS. IV. 



somewhat dry period ; the crop is here estimated to contain 

 54 -5ft. nitrogen per acre, which, added to the amount lost 

 in drainage, 29 '7ft., makes a total for amount of nitrogen 

 converted into nitrates of only 84'2ft.; less than half that 

 produced on the fallow cases.] 



With reference to the loss of other constituents in drainage 

 waters, Stoklasa" has determined the amount of calcium car- 

 bonate in drainage waters from soils derived from primitive 

 rocks, from chalk, and from peaty soils. He estimates the 

 yearly loss of calcium carbonate in soils from primitive rocks 

 at over 560 kilos per hectare (500ft. per acre)t and at about 

 3000 kilos per hectare (2700ft. per acre) in soils from chalk. 

 Its amount is increased by the application of ammonium com- 

 pounds owing to the acid of these salts being converted into 

 calcium salts by interaction with calcium carbonate, and also 

 to the formation of the very soluble calcium nitrate from nitri- 

 fication. He also gives the amounts of phosphoric acid found 

 in the drainage water from (1) loam from granite and gneiss 

 formations, (2) clay from the Permian, (3) marl, (4) humic 

 soil. The results were as follows : 



Loamy soil. Clay soil. Marl. Humk- soil. 



Total P 2 O 5 in soils ... 0-024 0-087 0-125 0-008% 



P a O 5 in drainage, per million 0*620 0-420 0*700 1-010 

 Estimated loss, ft. per acre 12-00 8-13 13-60 19-60 



This shows the enormous loss of phosphoric acid from humic 

 soils, although they contain only very small quantities. This 

 great loss is doubtless due to the solvent action of the large 

 quantities of carbon dioxide contained in the drainage of such 

 soils. 



Few determinations of the amount of potash in drainage 

 waters have been published. 



Its amount is probably always very small and the loss of 

 potash from this cause is seldom a matter of much importance. 

 Any potash which becomes soluble, or is applied in a soluble 

 form as manure, appears to be to a great extent held firmly in 

 the upper layers of the soil 4 



Lamlwirth. Versuchs. Stat. 1894, 45, 161. 

 Lawes, ( 

 about half thi 



t Lawes, Gilbert, and Warington (J. Roy. Agric. Soc. 1882, 1) estimate the loss at 

 is at Rothamsted, on tinmanured land. t H. Liebig, J.C.S. 1872, 318. 



