THE CONTROL OF SOIL-MOISTURE 219 



than three inches deep. Late in the season, especially for 

 corn, the cultivation should be shallow to prevent root-prun- 

 ing.^ 



For many years cultivation for a soil-mulch has been ad- 

 vocated for two reasons: (1) checking of evaporation, and (2) 

 the killing of weeds. Either procedure, if successful, will 

 allow the crop a larger proportion of the rainfall. Recent 

 experimental results, however, seem to indicate that a soil- 

 mulch with an intertilled crop does not check evaporation 

 compared with a soil uncultivated and kept free of weeds. 

 This is probably due to the fact, that even with moisture 

 a limiting factor, the water sacrificed in renewing the mulch 

 is not offset by that conserved. The tendency of soils, espe- 

 cially those of a sandy character to self -mulch as well as the 

 action of the roots of the crop in intercepting the water, may 

 also be factors. Under greenhouse conditions and in regions 

 of very little rainfall, the soil-mulch probably does conserve 



^ Since a great many of the inter-tilled crops are shallow-rooted, 

 great care should be exercised in cultivation, especially toward the latter 

 part of the growing season. Corn and j^otatoes are especially influenced 

 by root-pruning. The following data^ averaged for 7 years are 

 pertinent : 



Influence of Eoot-Pruning on the Yield of Corn in Bushels to 



THE Acre. Average of 7 Years. University 



op Illinois 



Treatment 



No cultivation, weeds kept down with hoe. 



Shallow cultivation 



Deep cultivation , 



Shallow cultivation, roots unpruned 



Shallow cultivatiouj roots pruned with knife. 



Surface scraped, roots unpruned 



Surface scraped, roots pruned with knife. 



Yield 



67.7 

 70.8 

 68.6 



74.8 

 61.6 



80.7 

 68,3 



2 Hosier, J. G., and Gustaf son, A. F., Soil Moisture and Tillage for 

 Corn; 111. Agr. Exp. Sta., Bui, 181, 1915. 



