122 TILLAGEMOVEMENTS OF SOIL WATER [chap. 



of rain, which is quite half as much again as would 

 be accounted for by the crop on the assumption that 

 only two tons or so of dry matter had been grown at 

 the date of sampling. 



Another example of the withdrawal of water from 

 the soil by the crop is seen in the proportions of water 

 in the soil of certain of the permanent grass plots at 

 Rothamsted, taken in July of the same year, 1870 



Down to the depth of 54 inches the plot receiving 

 minerals and ammonium salts contained 200 tons, and the 

 plot receiving minerals and nitrate 325 tons, less water 

 than the unmanured plot, quantities in this case some- 

 what less than would be indicated by the amount of 

 dry matter produced. 



There are two important cases in which the drying 

 effect of vegetation needs to be taken into account, in 

 the use of catch crops and in the planting of fruit trees. 

 On the lighter lands of the south of England catch 

 crops are not uncommonly taken on the land before 

 roots. The stubbles are quickly broken up, and 



