Orchard Culture — General Statements. 27 



and continue until the close of the growth period. It 

 may continue somewhat later with entirely hardy trees, 

 but where the trees are liable to winter injury, moderate 

 drying of the soil should be encouraged in late summer and 

 autumn. In regions where irrigation is practiced, this is 

 readily accomplished by withholding water. In other lo- 

 calities, dryness of the soil may be promoted b}' ceasing 

 cultivation and sowing a " cover crop." 



30, Coyer crops are useful (a) in taking up excessive 

 moisture from the soil late in the season, (b) in preventing 

 wash and loss of fertility during fall, winter and spring, 



(c) in preventing deep freezing of the ground in winter, 



(d) in hastening drying of the ground in early spring, and 



(e) in supplying the soil with humus and sometimes with 

 nitrogen. A cover crop should be sown, as a rule, about 

 midsummer, or as the normal growth period ends. The 

 leguminous crops are useful as cover crops on soils defi- 

 cient in nitrogen, since they enrich the soil with this ele- 

 ment; but on rich land on which trees tend to grow very 

 rapidly, a cover crop that adds no nitrogen to the soil is 

 preferable. The particular cover crop to be selected will 

 depend upon the season, the climate and the physical con- 

 dition of the soil. In dry seasons and climates, and on land 

 not in the best condition, the larger-seeded crops will usu- 

 ally prove more reliable than the smaller-seeded ones. In 

 all cases, a sufficient amount of seed should be sown per 

 acre to furnish growth enough to make a good mat of 

 herbage over the soil at the beginning of winter. 



Of the nitrogen-gathering cover crops, the clovers, cow 

 peas, vetches, peas and beans are available. 



Of the non-nitrogen-gathering cover crops, rye and other 

 cereals, buckwheat, millet, turnips and rape may be used. 



