174 



Farmyard Manure. 



[JUNE, 



Table XV. — Percentages of Water in Rothamsted Soils. 



Depth. 



Broadbalk Wheat. 



Hogs Barley. 



Unmanured. 



1 



Dunged. 



Unmanured. 



Dunged. 



0-9 inch .. 

 9-18 „ .. 

 18-27 » •• 



Per cent. 

 i6 - o 

 19-8 

 23-3 



Per cent. 



19*3 



17- 0 



18- 4 



Per cent. 

 17-0 



22'5 

 22" I 



Per cent. 

 20-7 



17- 7 



18- 3 



It is thus seen that in both cases the dunged soil, rich in 

 humus, had retained more of the comparatively recent rainfall 

 near the surface, so that the top soil was moister while the 

 subsoil was dryer. The difference in favour of the- surface 

 soil is about 3*5 per cent., which on that soil would amount 

 to about 30 tons per acre or approximately 0*3 in. of rain. 

 It is thus seen that the surface soil of the dunged plot had 

 retained practically the whole of the preceding rainfall, and 

 the greater dryness of the subsoil is due to the way the soil 

 has kept back the small rainfalls, which have evaporated 

 instead of being passed on to the subsoil, as happens on the 

 unmanured plots. The same fact is illustrated by the behaviour 

 of the drains which run below the centre of each of the wheat 

 plots at a depth of 30 in. ; below the dunged plot the drain 

 very rarely runs, only after an exceptionally heavy and con- 

 tinued fall, whereas the drain below the unmanured plot runs 

 two or three times every winter. Putting aside the greater 

 drying effect of the much larger crop on the dunged plot the 

 difference is mainly due to the way the surface soil rich in 

 humus first of all absorbs more of the water and then lets 

 the excess percolate so much more slowly that the descending 

 layer of over-saturation, which causes the drain to run, rarely 

 or never forms. 



The water-retaining power of the dung may also be seen 

 in the superior yield of the dunged plots in markedly dry 

 seasons. A comparison of the yield of wheat in bushels on 

 Plot 2, receiving 14 tons of dung, and Plot 7, receiving a 

 complete artificial manure, for the years 1879, which was 

 exceptionally wet and cold, and 1893, which was hot and dry 

 throughout the growing epriod of the plant, is given below. 



