220 FARMYARD MANURE [chap. 



dunged plots respectively, calculated as percentages of 

 the fine earth from which the stones had been sifted. 



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 drier. 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 inch 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 lie 

 below the centre of each of the wheat plots at a depth 

 of 30 inches ; below the dunged plot the drain very 

 rarely runs — only after an exceptionally heavy and 

 long-continued 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 absorbs 

 more of the water at first, 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. Table LXX. shows a com- 

 parison of the yield 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 for 1893, which was hot and dry throughout 



