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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Summer 2001 Summary: Over the past five years we have conducted considerable research into the unique effectiveness of targeted boron (B) fertilization and have ob- served that foliar B applications fre- quently increase fruit set and yield if applied during reproductive growth. Biochemical, isotopic, and molecular experimentation demonstrate that a transient B deficiency is common dur- ing reproductive growth and that B plays a unique but poorly understood role in reproduction. A transient nutri- ent deficiency is a short-term deficiency that occurs during a specific period of crop development, such as during flow- ering or seed fill. Although this research on B clearly demonstrates that transient nutrient deficiencies occur and have important effects on tree yields, there is inad- equate research to verify if transient deficiencies of other elements occur, or to determine if fluid fertilizers are the most efficient method of correction. Verifying the importance of transient deficiencies would provide a rationale for the use of fluid fertilizers in horticul- tural, field, and row crops. Such verifi- cation also represents a significant and important research challenge. Fluid fertilizers are used in U.S. agri- culture as both a replacement for solids and for their unique capacity to provide nutrients quickly and effectively. The use of fluids often allows for highly lo- calized and specifically tailored nutrient applications that are not as easily pro- vided using solid or blended products. Very little research is available, however, that demonstrates the unique value of fluid fertilizers and the role they play in providing a balanced nutrient supply. Although foliar fertilizers represent only a subset of all fluid fertilizers, re- cent advances in application of foliars to provide balanced nutrition and resolve short-term nutrient deficiencies offer valuable lessons. Foliars have been used by fruit grow- ers since the early 19th century and have become an important management prac- tice in all well-managed orchards. Sup- Dr. Patrick Brown Can Boron Correct Transient Nutrient Deficiencies? Recent California experiments using foliar applications seem to indicate so. More research is needed. plying nutrients by foliars is expensive however, requiring careful consideration of both cost and relative benefit when compared with conventional soil appli- cations. Foliar application is well justified un- der soil conditions that limit nutrient solubility as a consequence of 1) unfa- vorable pH or chemical composition of the nutrient, 2) where there are excess soil concentrations of competing ions or 3) where there are unfavorable condi- tions for root growth and nutrient up- take. To this end a wide variety of chemical formulations are available to help supply nutrients that are made un- available under certain soil conditions. Foliars are also used frequently in the ornamental and turf industry where 50 28-Feb Figure 1. Effect of application date of foliar B (5 lbs /100 gal) on yield and leaf B in pistachio, Brown, U of C al. Solubor 19-Mar 3-Apr 17-Apr 8-May 52 54 56 58 60 62 64 66 Yield - lbs/tree Yield Leaf B Leaf B ppm 500 450 400 350 300 250 200 150 100
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