36 SOILS AND FERTILIZERS 



lowed by surface cultivation. Evaporation may take 

 place from unplowed land during the fall, and in the 

 spring the soil contains appreciably less water than 

 plowed land. By fall .plowing it is possible to carry 

 over a water balance in 'the soil from one year to the 

 next. 



31. Spring Plowing. — When land is plowed late in 

 the spring there has been a previous loss of water by 

 evaporation, and the soil has not been able to store up 

 as much of the rain and snow as if fall plowing had 

 been practiced. 14 Dry soil is plowed under and moist 

 soil brought to the surface. This moisture is readily 

 lost by evaporation if surface cultivation is not em- 

 ployed ; good capillary connection of the surface soil 

 and subsoil is not obtained, and the furrow slice soon 

 becomes dry. 



Surface cultivation should immediately follow both 

 spring and fall plowing. 



Per cent, of water in* 3 

 Fall plowed Spring plowed 



April 25 land. land. 



From 2 to 6 inches 24.7 22.4 



" 6 to 12 " 26.6 24.1 



" 12 to 18 " 28.8 26.5 



Average difference 2.37 per cent. 



32. Mulching. — The use of well-rotted manure or 

 straw, spread over the surface as a mulch, prevents 

 evaporation. In forests the leaves form a mulch 

 which is an important factor in maintaining the water 

 supply. In order that a mulch be effectual, it must 



