THE ORCHARD DISTRICTS OF CALIFORNIA. 9 



NORTHERN CITRUS SECTION. 



The northern citrus section, as previously stated, comprises a small 

 region in the San Joaquin Valley, centering about Porterville and 

 Exeter, and a smaller section in the Sacramento Valley, centering 

 about Oroville and Palermo, besides small areas in various parts of 

 the valleys and foothills of the State. The conditions in this district 

 differ very much from the conditions in the southern California dis- 

 trict, and in these differences is found the reason why green-manure 

 crops have been but little used. 



The seasonal conditions at the north wliile favorable to the growth 

 of green-manure crops are less favorable for their handling. The 

 rainy season is quite definite, extending through January and Feb- 

 ruary, and sometimes into March. The soil, which is heavy, dries out 

 slowly during the winter season, often making it impossible to get 

 into the orchard to turn under a crop at the proper time. Thus, when 

 the season for turning under is delayed, a heavy vegetative growth is 

 objectionable in that it makes the land hard to work and at the same 

 time by shading prevents it from drying out to allow of cultivation 

 as early as otherwise would be the case. The soils throughout the 

 northern district are with few exceptions of the very heavy nature 

 referred to, and for this reason a heavy vegetative growth is often a 

 hindrance to proper handling. While the immediate effects of a 

 green-manure crop may be undesirable, there is but httle question 

 that these lands need to be made lighter by the addition of humus, 

 and results that appear at the time as unfavorable can well be toler- 

 ated when the ultimate effect will be an improved condition. 



Green manures have been used but little in the northern citrus 

 section. However, the results from a few plantings, together with 

 the experimental work done, clearly show that by early seeding a 

 good green-manure crop can be grown and in most cases can be 

 profitably used. 



DECIDUOUS ORCHARD SECTIONS. 



While the deciduous orchards are scattered throughout the State 

 of California they are largely in the northern part and are mostly 

 located on the fertile lands of the various river valleys and the low 

 foothills. Green-manure crops have not been used to any extent in 

 these orchards, and practically the only thing approaching such a crop 

 is the volunteer growth of bur clover, which is usually sufficient by 

 the time the orchards are plowed in the spring to yield considerable 

 humus. 



The problem of growing a green-manure crop in deciduous orchards 

 is quite different from that of growing the same crop ih citrus 

 orchards. This difference lies principally in the fact that the former 

 52810°— Bull. 190—10 2 



