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Fluid Journal : Fluid Journal 1996-1998
2 Fluid Journal Fall 1996 with the conventional treatments. Leaf concentrations. Only minor differences were noted with respect to leaf mineral content due to fertilization. The combination treatments had a higher leaf N content in one of four years and lower K in one of four years. No differences were noted in leaf Ca and P concentrations for any of the years. Although it was not noticeable in the trees, leaf N concentrations for one season were below the optimum range. The low concentrations were possibly due to sampling older leaves resulting from an early spring flush, and a September sampling date. Leaf P, K, and Ca levels were at or slightly below optimum ranges throughout the four years of the experiment. Fruit size. Fruit is sized at the packing house in accordance with how many fit in a four-fifths bushel carton (the larger the number, the smaller the fruit). During the three seasons that fruit size was measured, no statistical differences were noted in the percentage of fruit in any of the size cate-gories. However, the median fruit size in the 1989/90 and 1991/92 seasons was 36 for the conventionally treated plots while the median for the combination-treated plots was a size smaller at 40. When the percentages of each size were averaged for the three years, the conventionally treated plots tended to have a slightly higher percentage of the measured fruit in the bigger sizes (Figure 3). The conven-tionally treated plots averaged 36 percent of fruit size 36 and larger, compared With 32 percent for the plots receiving combination treatments. Juice quality. The only differences in juice quality between treatments occurred during the first year of the study when the fruit from the combination treatments was larger and had a slightly lower Brix content than the fruit receiving the conventional treatments. Climatic factors There were large year-to-year varia-tions in the overall fruit production resulting from climatic factors and tree physiological response. Temperature. Yields in the 1989/90 season were greatly reduced from the previous season due to a low fruit set caused by sub-freezing temperatures in February. Production rebounded in the 1990/9 1 season with exceptionally Figure 1. Mean fruit yield by fertilization on "Ruby Red" grapefruit rees, Boman, University of Florida, 1988-92. Figure 2. Four-year cumulative TSS and fruit yield advantage of combination treatments over conventional treatments, Boman, University of Florida, 1988-92. 1988/89 0 200 400 600 800 Fruit Yield (box/A) Dry+Fertigate 3 Dry Applications 1989/90 1990/91 1991/92 1988/89 Box/A increase for Dry+Fertigate 0 30 60 90 120 150 180 4-Year Totals Dry + Fertigate Yield 3 Dry apps: 1897 box/A 2071Box/A 9744 lv TSS/A 9048 lb TSS/A 0 120 240 360 480 600 720 1989/90 Production Season 1990/91 1991/92 TSS lb/A increase for Dry+Fertigate
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