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Fluid Journal : Fluid Journal 1993-1995
1 Fluid Journal Spring 1995 Drs. Patrick H. Brown, Louise Ferguson, and Geno Picchioni Boron Boosts Pistachio Yields California researchers find foliar applications are most effective after three- year trials. Timing of application is critical. Table 1. Effect of application date of foliar boron (5 pounds of Solubor/100 gals) on pistachio yield and leaf boron, Brown et al., University of California. Yield Leaf Boron Application Date Growth Stage lbs (July) micro-g February 28 Late dormant 64 188 March 19 Early bud break 52 188 April 3 Flowering 54 187 April 17 Leafing out 51 256 May 8 Fully leafed out 52 468 02510 246 8 lbs/100 gals oz/tree Rate of application 124 122 120 118 116 114 112 110 108 106 104 102 100 98 Foliar Applied Soil Applied Yield - lbs/tree Figure 1. Influence of boron (soil or foliar) on pistachio yield, three-year average, Brown, et al., University of California. Summary: Boron supplementation applied on pistachio trees in the late dormant stage increases germination, reduces blanking as well as non-splits, and, consequently, increases yield. Soil applications of boron are effective in raising leaf boron levels, but are not as effective as foliar sprays at increasing yield. Recommended rates of boron application most effective in raising yields are between 2 and 5 lbs Solubor/ 100 gals. Timing of foliar applications of boron is critical. Late dormant sprays (just prior to bud swell through to 20 percent bud break) are the most effective. Enhanced yield response to boron sprays may decrease yield in the following off-year effectively enhancing alternate bearing. At the site used here, boron sprays produced a net yield increase of approximately 20 percent over two veers. Based on the results of this work, it is suggested that pistachio growers provide supplemental boron sprays at the rate of 2 to 5 lbs Solubor/100 gals during the late dormant or early bud break stage. These recommendations are based on research in two soil types in plants with average tissue summer boron levels of 150 to 190 ppm. The validity of these recommendations in different soils and environmental conditions is being assessed. Boron deficiency occurs widely in the fruit growing regions of California. It is a limiting element in many pistachio growing regions of the central valleys. Boron deficiency results in characteristic leaf symptoms that can be alleviated with the additions of boron fertilizer. Boron long has been recognized as an essential element for plant growth. However, its role and mode of action are unknown. Boron has been reported to be involved in such diverse processes as nucleic acid metabolism, cell division, sugar biosynthesis and translocation. and membrane functions. The role boron plays in the flowering and fruiting process, however, is unclear. There is an immediate need, therefore, to understand how boron moves through the soil and plant, and
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