MULCHED-BASIN SYSTEM OF IRRIGATED CITRUS CULTURE. 23 
The average annual yield per tree of the 8-acre tract since the 
basins were installed has been 5.5 boxes per tree,1 while the average 
annual yield of the unbasined trees during the same period has been 
3.2 boxes per tree, the same as during the preceding period. 
It is not possible to differentiate sharply in this case between the 
effect of mulching and other factors which led to higher yields from 
the 8-acre tract previous to mulching. Assuming the 10-acre tract 
to constitute a fair check, the yield of the 8-acre tract has been 
increased 12 per cent by the installation of the basins.” ; 
SIZE OF BASINS. 
The basins in the Sunny Mountain experimental tract extended 
to the middle of the furrow row and included the entire soil surface. 
This type of basin requires the most mulching material and is conse- 
quently the most expensive to maintain. In following this plan it 
is necessary to restrict the basins between every fifth and sixth row 
of trees sufficiently to provide a roadway to haul out fruit, bring in 
the mulching material, and distribute fire pots and oil when frost 
protection is necessary. With this type of basin all of the soil is 
irrigated and available for the development of the root system of the 
tree. If all of this soil is not necessary for an adequate root develop- 
ment, then a restricted basin system may be used. Certainly all of 
the soil is not utilized to the best advantage in the present system of 
furrow irrigation, for the soil under the tree during the summer is 
so dry as to make the development of feeding roots practically impos- 
sible. From the marked response and increased vigor of the trees 
under the basin system in the Victoria and Vivienda experimental 
tracts, where restricted basins were used, it appears that the basins 
can be reduced somewhat below the maximum area without detri- 
ment to the trees and with a corresponding reduction in the cost 
of maintenance. 
With restricted basins, measuring 10 by 20 feet in a grove planted 
20 feet each way, a cover crop can also be grown between the tree 
rows during the rainy months to supply part of the mulching mate- 
rial. The summer growth on these interrow strips, which without 
irrigation will necessarily be limited, can also be cut and apphed 
to the basins when sufficient in quantity to justify the labor. If 
extra water is available, these interstrips may be irrigated and the 
1This is based upon the yield of only one-half the tract in 1915-16. The remaining 
portion was seriously damaged through the use of an oil spray for scale in 1915, resulting 
in a heavy drop of leaves and fruit and reducing the yield of the sprayed portion to less 
than half that of the unsprayed trees. 
2The crop on the trees at the present writing (September, 1916) is also much better on 
the mulched-basin tract than on the adjoining grove, in spite of the fact that the 8-acre 
tract is badly infested with scale. 
i er i rs es ers ee ot 
%. §4= SE. 
