MULCHED-BAS1N SYSTEM OF IRRIGATED CITRUS CULTURE. 2.'> 



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. 2 



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 applied 

 to the basins when sufficient in quantity to justify the labor. If 

 extra water is available, these interstrips may be irrigated and the 



1 This 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. 



2 The 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. 



