12 



IMPROVEMENT OF THE WHEAT CROP IN CALIFORNIA. 



plowings. This is due largely to a more or less packed condition of 

 the subsoil. Deep plowing should be done in the early spring while 

 there is still sufficient moisture in the soil. It should not be done 

 while the soil is either too wet or too dry. While the benefits derived 

 from deep plowing may not be so evident the first season, the results 

 obtained are of permanent character. The subsoil is benefited by 

 direct contact with the air and other climatic influences, and the 



effects of deep plow- 

 ing will be more 

 noticeable the sec- 

 ond and succeeding 

 years. 



Addition of Humus and 

 Nitrogen to the Soil. 



As already stated 

 the soil of California 

 grain lands is low in 

 humus. In order to 

 add humus to the 

 soil green - manure 

 crops must be 

 grown and plowed 

 under. This is nec- 

 essary not only in 

 order that land very 

 low in humus be 

 again placed in good 

 condition, but also 

 that lands in which 

 humus is now fairly 

 plentiful be retained 

 in good shape (fig. 1). 

 Owing to a tendency 



Fig. 1— Wheat plants from six plats treated differently, showing com- Q f very light sandy 

 parative development: A , From plat continuously seeded to wheat; *? 



B, from plat barefallowed in 1908; C, from plat upon which horse SOU to Sllltt ( Hiring 



beans were grown and plowed under in 1908; D, from plat upon heavy winds, deep 

 which Canadian field peas were grown and plowed under in 1908; E, . i i , 



from plat upon which rye and vetch were grown and plowed under plowing may De Uet- 



in 1908; F, from plat upon which rye was grown and plowed under fUneiltal at first Oil 



in 1908 - such soils. This soil 



shifting may, however, be reduced to a minimum by the addition of 

 humus, which will give it body and make possible the practice of deep 

 plowing without injury. 



178 



