64 Elementary Principles of Agriculture 



1. Not mulched. (Check or control.) 



2. Surface cultivated one inch deep (soil mulch). 



3. Surface cultivated two inches deep (soil mulch). 



4. Mulch with one inch of coarse gravel. 



5. Mulch with one inch of sawdust. 



6. Mulch with one inch of fine sand. 



7. Mulch with one inch of fine cut straw. 

 Which mulch is most effective? 



Which mulch is most practical under field conditions? 

 What other conditions affect evaporation from the soil? 



96. Soil Moisture Retained by Cultivation. Professor 

 King has investigated the efficiency of surface culti- 

 vation in retaining water in the soil. A piece of fallow 

 ground was divided into plots twelve feet wide, as shown 

 in diagram in Fig. 36. Three were cultivated and two 

 left fallow. The figures in the table show the percentage 

 of water in the soil of each plot, at different depths, at 

 the end of fifty-nine days. The average loss of water 

 from the cultivated plots was 709.4 tons per acre, while 

 in the non-cultivated plots the loss was 862.3 tons 

 per acre. This makes the mean daily loss of water 

 from the ground not cultivated 3.12 tons per acre 

 greater than was that from the cultivated soil. This 

 cultivation saved the equivalent of 7.9 inches rainfall. 

 The soil mulch is a great protection against temporary 

 drought. It saves the soil water for the plant to use in 

 making food; whereas, if allowed to evaporate from the 

 surface of the soil, it would be lost. The mulch should 

 be renewed after every rain. It seems strange, but it is 

 true, that a summer shower will destroy the mulch, and 

 cause the land to dry out so much faster that the soil will 

 contain less moisture after a few days than if it had not 

 rained at all. Such a shower moistens only the surface, 

 destroying the capillary spaces between the soil particles. 



