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Lawrence R. Parsons, Bahman Sheikh, Robert Holden and David W. York

The purpose of this article is to discuss several aspects of reclaimed water that are of importance today. Emphasis is placed on water reuse in Florida and California because they are two of the largest producers of reclaimed water in the United

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Thomas H. Yeager, Joseph K. von Merveldt and Claudia A. Larsen

The use of reclaimed water as an irrigation source for nursery crops is of increasing importance because many nurseries are located near urban areas that have experienced rapid population growth. Population growth results in increased demand for

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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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Jinghua Fan, George Hochmuth, Jason Kruse and Jerry Sartain

wastewater is increasingly viewed as a resource for supplying irrigation water and nutrients for landscapes ( Harivandi, 2004 ). Reclaimed water contains nutrients, such as N and P, which are essential plant nutrients. Currently, Florida is a leading user of

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Michael A. Maurer and Frederick S. Davies

Two field studies conducted from 1990 to 1991 evaluated the effects of reclaimed water on growth and development of 1- and 2-year-old `Redblush' grapefruit (Citrus paradisi Macf.) trees on Swingle citrumelo [Citrus paradisi (L.) Osb. ×Poncirus trifoliata (L.) Raf.] rootstock. Treatments were arranged as a3 (water sources) x 3 (irrigation levels) factorial at two locations on an Arredondo (well drained) and Kanapaha (poorly drained) fine sand near Gainesville, Fla. Irrigation treatments included 1) reclaimed water, 2) reclaimed water plus fertigation, and 3) well water plus fertigation. The reclaimed water was formulated to simulate that of a sewage treatment plant at Vero Beach, Fla. Irrigation was applied at 20% soil moisture depletion, or at 19 or 25 mm·week regardless of rainfall. In both experiments, visual ratings of tree vigor, and measured tree height and trunk diameter, were significantly lower for trees watered with reclaimed water without fertilizer than for the others in both years. Moreover, there was no fourth leaf flush in 1991 with reclaimed water. There was a significant increase in leaf Na, Cl, and B concentrations for the reclaimed water and reclaimed water plus fertigation treatments in 1990; however, in 1991 only leaf B concentrations showed a similar trend. In 1991, there were no significant differences in leaf Cl concentrations. Visual symptoms of N deficiency were observed by the end of the first season in trees grown with reclaimed water. Irrigation levels generallv did not affect tree growth.

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Ursula Schuch

Four species of salt-sensitive perennials (Chilopsis linearis, Tecoma stans, Salviagreggii, and Verbena pulchella gracilior) were grown in containers and were irrigated with potable or reclaimed water. Electrical conductivity (EC) was 0.3 dS·m-1 for potable irrigation water and 1.0 dS·m-1 for reclaimed irrigation water. After 12 weeks of growing plants with reclaimed vs. potable water, C. linearis leaf dry weight was reduced by 15%, T. stans root dry weight was reduced by 41%, V. puchella gracilior stem dry weight was reduced by 35%, and S. greggii total dry weight was reduced by 56%. The increase in canopy size was calculated 4, 8, and 12 weeks after treatments began and was not affected by water source for C. linearis and T. stans, but was reduced for S. greggii and V. pulchella gracilior treated with reclaimed water. Up to 12% dieback and reduced flowering were observed on S. greggii irrigated with reclaimed water. Within 4 weeks of treatments, EC in the root zone was 0.5 dS·m-1 for plants irrigated with potable water and 1.9 dS·m-1 for those irrigated with reclaimed water. When exposed to drought, C. linearis and T. stans grown with reclaimed water maintained a more negative water potential as soil moisture was depleted. Osmotic potential started to increase significantly for both irrigation treatments when more than 25% moisture from fully saturated containers were lost. In general, plants irrigated with potable water sustained more damage than those irrigated with reclaimed water after recovering from a drought cycle.

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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.

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M.A. Maurer, F.S. Davies and D.A. Graetz

A field study was conducted on mature `Redblush' grapefruit trees (Citrus paradisi Macf.) on sour orange (Citrus aurantium L.) rootstock from 1991 to 1993 near Vero Beach, Fla. on poorly drained (flatwoods) soil to determine the effects of reclaimed water on leaf, soil and shallow well-water nutrients. Treatments consisted of a canal water applied based on soil moisture depletion, and reclaimed water applied at 23.1, 30.7 and 36.6 mm/wk. Reclaimed water treatments received supplemental fertilization in addition to the N present in the water. All treatments received about 130 kg/ha/yr N. Leaf tissue N, P, K, Ca, Mg and Na concentrations were similar for all treatments, but B concentrations were significantly higher for the reclaimed water treatments in 1991 and 1993. Soil P and Na concentrations also increased in the reclaimed water treatments. Water samples taken from shallow depth wells showed that reclaimed water treatments had lower levels of NO, compared to the control possibly due to leaching. Reclaimed water contained only trace or undetectable levels of heavy metals.

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M.A. Maurer and F.S. Davies

Field studies conducted over two growing seasons were designed to study the effects of reclaimed water on the development of 1-and 2-year old `Redblush' grapefruit trees (Citrus paradisi Macf.) on Swingle citrumelo rootstock. Experiments were conducted at two locations on Kanapaha and Arredondo fine sands and treatments were arranged in a 3×3 factorial experiment. Treatments included reclaimed water, well water plus fertigation and reclaimed water plus fertigation, which received <0.023, 0.23 and 0.23kg N/tree/yr in 1990, and <0.034, 0.34 and 0.34kg N/tree/yr in 1991, respectively. In addition irrigation was applied at 20% soil moisture depletion, 1.5 cm/wk and 2.5 cm/wk for 31 weeks in 1990 and 39 weeks in 1991. Tree growth and vigor were greatest for the reclaimed water plus fertigation based on visual ratings and trunk diameter measurements and lowest for reclaimed water alone, where leaves exhibited visual signs of N deficiency. No differences in tree growth or vigor were observed among irrigation rates. Similar results were observed at both experimental locations.

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Lawrence R. Parsons, T. Adair Wheaton and William S. Castle

Conversion of wastewater to reclaimed water for crop irrigation conserves water and is an effective way to handle a growing urban problem: the disposal of wastewater. Water Conserv II is a large reclaimed water project developed by Orlando and Orange County, Fla., that presently irrigates ≈1900 ha of citrus. The project includes a research component to evaluate the response of citrus to irrigation using reclaimed water. Citrus trees in an experimental planting responded well to very high application rates of reclaimed water. Irrigation treatments included annual applications of 400 mm of well water, and 400, 1250, and 2500 mm of reclaimed water. The 2500-mm rate is excessive, and since disposal was of interest, this rate was used to determine if citrus could tolerate such high rates of irrigation. The effects of these treatments were compared on `Hamlin' orange [Citrus sinensis (L.) Osb.] and `Orlando' tangelo (C. paradisi Macf. × C. reticulata Blanco) combined with four rootstocks: Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.], Cleopatra mandarin (C. reticulata Blanco), sour orange (C. aurantium L.), and Swingle citrumelo (C. paradisi × P. trifoliata). Growth and fruit production were greatest at the highest irrigation rate. Concentration of soluble solids in the juice was usually lowered by the highest irrigation rate, but total soluble solids per hectare were 15.5% higher compared to the 400-mm rate, due to the greater fruit production. While fruit soluble solids were usually lowered by higher irrigation, the reduction in fruit soluble solids observed on three of the rootstocks did not occur in trees on Carrizo citrange. Fruit peel color score was lower but juice color score was higher at the highest irrigation rate. Crop efficiency (fruit production per unit of canopy volume) was usually lower at the 2500-mm rate and declined as trees grew older. Weed cover increased with increasing irrigation rate, but was controllable. Irrigation with high rates of reclaimed water provided a satisfactory disposal method for treated effluent, benefited growth and production of citrus, and eliminated the need for other sources of irrigation water. Reclaimed water, once believed to be a disposal problem in Florida, is now considered to be one way to meet irrigation demands.