INFLUENCE OF CULTIVATION 37 



be compacted, — a loose pile of straw is not a mulch. 

 In reclaiming lands gullied by water, mulching is 

 very beneficial. A slight mulch may also be used to 

 encourage the growth of grass on a refractory hillside. 

 When land is mulched, evaporation is checked. Sur- 

 face cultivation and mulchi: 

 excellent results obtained. 13 



face cultivation and mulching may be combined and 



Per cent, of water in 

 Mulched straw- 

 berry patch. Uumulched. 



Soil 2 to 5 inches 18.12 11.17 



" 6 to 12 <( 22.18 18.14 



" 12 to 18 " 24.31 21. 11 



33. Depth of Plowing. — The depth to which a soil 

 should be plowed in order to give the best results must, 

 of necessity, vary with the conditions. Deep plowing 

 of sandy land is not advisable, particularly in the 

 spring. On clay land deeper plowing should be the 

 rule. The longer a soil is cultivated the deeper and 

 more thorough should be the cultivation. While 

 shallow plowing is admissible on new prairie land, 

 deeper cultivation should be practiced when the land 

 has been cropped for a series of years. The depth of 

 plowing should be regulated by the season. In the 

 prairie regions, and in the northwestern part of the 

 United States, shallow plowing is more generally prac- 

 ticed than in the eastern states. Deep plowing in the 

 fall gives better results than in the spring. It is not 

 a wise plan to plow to the same depth every year. 

 Prof. Roberts says: 15 "If plowing is continued at one 



