280 SOILS: PROPERTIES AND MANAGEMENT 



If the wilting point of this soil is 6 per cent, the mulched 

 area contains more than twice as much available moisture. 

 This 3.8 per cent of available moisture by which the 

 mulched soil excels the unmulched is equivalent in a five- 

 foot depth to about 250 tons of water, enough to increase 

 the crop by a ton of dry matter — certainly not an insig- 

 nificant saving where crop yield and moisture are so very 

 closely correlated. 



A considerable amount of experimentation * is available 

 which seems to indicate that mulching a soil does not in- 

 crease its yield over a soil not so treated. One reason for 

 this, as already suggested, may be in the fact that water 

 may not have been the limiting factor, the rainfall having 

 been just right in amount and distribution. Again, the 

 roots may have so intercepted the capillary water as to 

 have allowed no more evaporation from the unmulched 

 soil than from the mulched. In some soils hard layers 

 often form which act in repelling capillary movement. 

 Such a condition would function as successfully in check- 

 ing losses as if a true mulch were present. In the study 

 of mulches and their value in increasing a crop, decided 

 opinions should not be advanced until every phase has 

 been thoroughly investigated regarding the exact factors 

 dominant in the determination of yield. The extended 

 use of soil mulches in the Corn-Belt and in dry-farming 

 operations argues for their benefits. 



198. Effect of mulches other than on moisture. — That 

 mulching a soil has other effects besides the conserving of 

 moisture is universally evident. In general the physical 

 condition of the soil is always better after a crop that has 



1 Cates, J. Si, and Cox, H. R. The Weed Factor in the 

 Cultivation of Corn. U. S. D. A., Bur. Plant Indus., Bui. 

 257. 1912. 



