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Fluid Journal : Fluid Journal 1996-1998
3 Fluid Journal Fall 1996 high yields for the block. Yields in the following season (199 1/92) were the lowest in the four-year period, partially as a result of the exceptional yields in the previous season and also due to a sporadic bloom caused by lack of winter dormancy, plus widely fluctuating spring temperatures. Moisture. One of the driest periods in recent times occurred during the first two-and-a-half years of the study. Normal annual rainfall is about 55 inches in the area of the trials. Only 42 inches of rainfall was recorded in the 1988/89 season (March 1988 through February 1989), followed by 45 inches in the 1989/90 season. The first half of 1990 was also very dry. However, summer rains brought relief to the extended drought. The 1990/91 rainfall was 46 inches. In 199 1/92, 59 inches of rain was recorded. Supplemental irrigation applied during dry periods resulted in total rain-fall plus irrigation averaging 65, 71, 64, and 65 inches for the 1988/89, 1989/90, 1990/91 and 1991/92 seasons, respectively. Higher water application in the 1989/90 season (23 inches of irrigation) was a result of drought in July through September when summer rains normally supply sufficient moisture. Methodology Application. Nitrogen and potassium were applied on the dates shown in Table 1 and at the rate of approximately 160 lbs/A per year. On the conventional plots, dry appli-cations were broadcast three times per year. About 33 percent of the annual nitrogen and potassium (plus minor ele-ments) was applied in late winter. The same applications were repeated in May/June and October/ November. On the combination plots a single broadcast application was made in February, applying again 33 percent of the nitrogen and potassium. The remain-ing 67 percent was applied throughout the growing season. A 10-0- 10 solution was injected into the irrigation water at the rate of 6 lbs/A of N and K20 every two weeks from April through early November. Grass/weed control. A herbicide strip was used in the tree rows to control grass and weeds. Soil. Experiment was conducted on a Pineda Fine Sand, which has about 6 inches of gray sand overlaying a yellowish-brown sand. A clay layer at a depth of about 3 feet provided a slowly perme-able barrier that perched the water table during high rainfall. Plots. Most beds contained eight plots with six or eight "Ruby Red" trees per plot. Plots consisted of three or four adjacent trees in a row plus matching trees in the row on the other side of the bed. Tree density was 87 trees/A. Leaf samples were collected for min-eral analysis during August or September of each year. Yield measurements were obtained for each randomized complete block design from the total weight of fruit produced on two trees from each plot. Fertigation beneficial This experiment suggests that with a properly designed and maintained microsprinkler system, broadcast fertilization combined with fertigation can provide enhanced returns for Flatwoods citrus growers. Dr. Boman is associate professor of agri-cultural engineering at the University of Florida, Indian River Research and Education Center Ft. Pierce. Figure 3. Three-season (1989-92) average percentage of measured fruit within each size category by fertilizer treatment, Boman, University of Florida. 64 0 4 8 12 16 20 1 Dry+Fertigate 3 Dry+Fertigate 564840363227 3-year average fruit size Percent of fruit
Fluid Journal 1993-1995
Fluid Journal 1999-2001