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 while 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 
ereen-manure crop may be undesirable, there is but little 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 in citrus 
orchards. This difference lies principally in the fact that the former 
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