IV.] 



HUMUS AND SOIL WATER 



117 



Effect of Dung on the retention of Water by the Soil. 



A soil which has been enriched in humus through 

 repeated applications of farmyard manure will resist 

 drought better than one in which the humus is low ; the 

 difference is seen not so much in the greater amount 

 of moisture present in the soil containing humus, as 

 in the way it will absorb a large amount of water 

 temporarily during heavy rainfall, and then let it 

 work more slowly down into the soil, thus keeping 

 it longer within reach of the crop. Good examples 

 are afforded by the Rothamsted plots; samples of 

 soil from the wheat land were taken on 13th September 

 1904, on the previous day 0262 inch of rain had 

 fallen, but for nine days before there had been little 

 or np rain. The portions of the plots from which 

 the samples were drawn had been fallowed through 

 the summer, so that the drying effect of the crop 

 is eliminated. Samples were also taken from the 

 barley plots on 3rd October of the same year; 0-456 

 inch of rain had fallen on the 30th September, before 

 which there had been fifteen days of fine weather. 

 The following table shows the water in the soil of the 

 unmanured and the continuously dunged plots respec- 

 tively, as percentages of the fine earth from which the 

 stones had been sifted 



Percentages of Water in Rothamsted Soils. 



