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Larry R. Parsons*

Florida is one of the larger producers of reclaimed water in the U.S., and use of this water has increased greatly in the past ten years. The objective of this study is to compare changes in reclaimed water use by different entities over the past several years. From 1986 to 2002, total reuse treatment capacity and flow in Florida increased by 221% and 183%, respectively. In the 1980s, reclaimed water was considered to be an urban disposal problem, and cities encouraged use of this water by giving it away for no charge. Because it was free, agricultural irrigation became the largest user of reclaimed water in the mid-1990s and is still one of the larger users. From 1992 to 2002, overall agricultural land area irrigated with reclaimed water increased by 77%. Land area of edible crops irrigated with reclaimed water increased during that period but remained relatively constant around 6070 ha after 1996. Irrigation of other crops increased to 9800 ha. Golf course irrigation increased by 212% to 20,476 ha while residential irrigation increased around 8147% to 33,373 ha during this period. Total flow to ground water recharge and industrial uses increased by 125% and 424%, respectively. While agricultural irrigation is still a large user of this water, other uses such as golf course, residential, groundwater recharge, and industrial are becoming more important. Some cities are no longer willing to provide this water to agriculture for no charge as competition from other entities increases. Agriculture may have to pay for the water, use less water, or develop other water sources.

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Larry R. Parsons* and Ed Etxeberria

Earlier work has shown that moderate water deficits imposed on citrus trees can increase fruit Brix without adversely affecting yield. Increased water restrictions have been imposed on citrus growers as Florida's population continues to increase. The objectives of this study were to determine: 1) the effects of no irrigation in the fall and winter on orange fruit quality parameters in Florida; and 2) amount of potential irrigation water savings. Trees were irrigated identically in the spring and summer. A non-irrigation treatment was started on Hamlin and Valencia oranges in September and October, respectively, while controls continued to be irrigated following established irrigation practices. An additional non-irrigated treatment was started at the same time on the Valencias that consisted of a soil covering with a water barrier (Tyvek) to exclude rainfall. Stem water potential was monitored during the fall and winter to estimate differences in water stress among the treatments. Brix and organic acids increased in fruit from non-irrigated treatments when compared to fruit from irrigated trees. Results also demonstrate that reduced irrigation did not affect yield greatly. Amount of irrigation savings was determined for both cultivars that differ in maturity dates.

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Larry R. Parsons and T. Adair Wheaton

Hamlin orange trees on Swingle rootstock planted in 1991 were subjected to six different rates of irrigation with approximately the same amounts of water applied either daily (1-day), every other day (2-day), or every 4th day (4-day). Rates provided from 0.43 to 1.95 of historical daily evapotranspiration (ET) applied to the wetted area. Irrigation was delayed following rainfall. The effects of irrigation rate and frequency on trunk and canopy growth, yield, soil water content, root distribution, and total water use were studied. There was little effect of irrigation rate or frequency during the first 2 years after planting. However, tree growth improved with increasing irrigation rate during the 3rd and 4th years, and growth in these years was greater when irrigation was scheduled daily. Effects of rate and frequency on growth were not as great as expected. Yield increased as irrigation increased in 1994. Leaf nitrogen was generally higher at the lower irrigation rate. Soil water content varied with depth. Extraction of soil water was more rapid in the top 45 cm of soil. Roots after 4 years did not extend below 45 cm with 60% of the roots in the top 15 cm and 90% in the top 30 cm. Roots were concentrated closer to the trunk for trees at the lower irrigation rates.

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Larry R. Parsons and T. Adair Wheaton

Wraps of fiberglass or other insulating material have frequently been used in Florida for cold protection of young citrus tree trunks. Traditional wraps were compared to a foil-covered plastic bubble material formed into cones. The base of the cone on the ground trapped soil heat and the apex was secured around the trunk at a height of 40 cm. Cones with base diameters of 15, 30, 45 and 60 cm were compared to a cylindrical wrap of the same material and other traditional wraps. A major freeze in Dec. 1989 killed unprotected control trees to the rootstock. Cones provided better freeze protection than other wraps. Temperatures inside the cones were generally warmer as cone diameter increased. By trapping soil heat, cones of this material can provide better freeze protection of young trees when irrigation or other heat sources are not available.

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Larry R. Parsons and T. Adair Wheaton

Undertree microsprinkler irrigation has protected 1 or 2 year old trees to a height of 1 meter during severe advective freezes. During the severe December 1989 freeze, microsprinklers elevated to 0.9 meter protected 5 year old citrus trees to a height of 2 meters. Limb breakage due to ice loading was negligible. Protection was achieved with water application rates less than half that required by some overhead sprinkler models. Survival is attributed to 1) continuous spray from the microsprinkler rather than periodic spray from a rotating overhead sprinkler, and 2) effective localized application rate on branches intercepting spray is more than average overall spray application rate. Elevated microsprinklers provide freeze protection to a greater height and allow for more rapid post-freeze recovery.

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Larry R. Parsons and T. Adair Wheaton

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Larry R. Parsons and T. Adair Wheaton

Highly treated sewage effluent water increasingly is being used for agricultural irrigation. This reclaimed water is presently being used in a large citrus irrigation project in central Florida. The purpose of this study was to determine the effects of high application rates of reclaimed water on growth and leaf mineral content of young citrus trees. High application rates (1270 and 2540 mm per year) of reclaimed wastewater were compared to a normal recommended rate of 406 mm per year of either reclaimed or well water. Tree growth was greater at the higher application rates, but these rates also promoted greater weed growth. With reclaimed water, leaf Na, Cl, and K contents generally increased with increasing irrigation rate, but these levels remained well below levels that would cause plant damage. Leaf Cl accumulation was much higher in `Hamlin' orange than `Orlando' tangelo. Rootstock also affected leaf Na and Cl accumulation. Reclaimed water appears to be a useful alternative to well water for citrus irrigation.

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Larry R. Parsons and T. Adair Wheaton

`Hamlin' oranges and `Orlando' tangelos on four rootstocks have been irrigated since planting in 1987 with highly treated reclaimed effluent water at application rates of ≈500, 1250, and 2500 mm/year. Reclaimed water treatments have been compared to a well water control at 500 mm/year. Tree growth, yield, and fruit quality have been satisfactory for all irrigation treatments. Growth and yield of `Orlando' tangelos was greatest at the 2500 mm rate and yield was highest on `Swingle' citrumelo and `Carrizo' citrange rootstocks. `Orlando' tangelos benefited more from the high irrigation rates than `Hamlin' oranges. Dilution of soluble solids in the juice by high irrigation rates has diminished as trees matured. Leaf nutrient content was influenced by irrigation, variety, and rootstock. Reclaimed water supplied all the phosphorous and boron needed for citrus production. Soil pH increased due to irrigation with reclaimed water. No disease problems have resulted from the high irrigation rates. Irrigation with high rates of reclaimed water on deep well-drained sands is not detrimental and has benefited citrus production.