Results Irrigation with reclaimed water increased mineral residues in the soil profile, altered leaf mineral concentration and fruit quality, and promoted better tree performance and more weed growth relative to irrigation with well water. Higher accumulation of nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) in soils irrigated with reclaimed water were not significantly reflected in leaf mineral status. Although leaf sodium (Na), chloride (Cl), and boron (B) concentrations were noticeably higher in reclaimed water treatments than in those of well water, they are still far below the toxicity levels.

Conclusions Overall, blocks irrigated with reclaimed water had trees with denser canopy, greener leaves, and heavier bloom and fruit crop than the control blocks. Weed growth was generally rated higher in blocks watered with reclaimed water than that in well watered blocks. This highly treated wastewater in central Florida has been found to be a very safe and a good option for increasing water supplies, but not a significant source of plant nutrients to citrus trees.

Effects of Irrigation with Reclaimed Municipal Wastewater on Citrus Trees Effects of Irrigation with Reclaimed Municipal Wastewater on Citrus Trees Mongi Zekri1, Lawrence R. Parsons2 and Robert C. J. Koo2

1University of Florida, IFAS, Hendry County Extension Office, P.O. Box 68, LaBelle, FL 33975, USA2University of Florida, IFAS, Citrus Research and Education Center, 700 Experiment Station Road,, Lake Alfred, FL 33850, USA

Distribution center of reclaimed water & citrus groves Rapid infiltration basins & citrus groves

Citrus grove on a lake

IntroductionWater restrictions on the use of available groundwater for irrigation are becoming more severe. Disposal of sewage wastewater is also a problem of increasing importance throughout the world. Both the need to conserve water and to safely and economically dispose of wastewater make the use of treated wastewater in agriculture a feasible option.

ObjectiveTo investigate the long‑term use of reclaimed wastewater for citrus irrigation.

Experimental DesignThirty to thirty‑two sites were selected in citrus groves located in Lake and Orange Counties in Florida. Eight to nine of these sites were located in groves where well water was used for irrigation. These sites were regarded as controls. The effects of irrigation with reclaimed wastewater and well water on soil water content, soil chemical analysis, leaf mineral status, fruit quality, and visual appearance of citrus trees were compared.

Characteristic

Max. averageconc. limits

Well waterMean + SD

Reclaimed waterMean + SD

pH 6.5‑8.4 7.9 + 0.3 7.1 + 0.2

TDS (mg L-1) 704 135 + 25 325 + 25

Element mg L‑1 mg L -1 mg L-1

Total nitrogen 30 7 + 2 10 + 3

Nitrate nitrogen ‑‑ 5 + 2 8 + 2

Phosphorus 10 0.09 + 0.04 4 + 2

Potassium 30 1.6 + 0.6 14 + 3

Calcium 200 33 + 6 42 + 4

Characteristic Max. averageconc. limits

Well waterMean + SD

Reclaimed waterMean + SD

Magnesium 25 7 + 1 9 + 1

Sodium 70 5 + 2 62 + 7

Chloride 100 11 + 3 69 + 7

Copper 0.20 0.03 + 0.02 0.03 + 0.02

Zinc 1.0 0.02 + 0.02 0.06 + 0.02

Manganese 0.20 0.01 + 0.01 0.01 + 0.01

Iron 5 0.02 + 0.02 0.07 + 0.03

Boron 1.0 0.02 + 0.01 0.14 + 0.03

Koo, R.C.J. and M. Zekri. 1989. Citrus irrigation with reclaimed municipal wastewater. Proc. Fla. State Hort. Soc. 102:52-56. Zekri, M. and R.C.J. Koo. 1990. Effects of reclaimed wastewater on leaf and soil mineral composition and fruit quality of citrus. Proc. Fla. State Hort. Soc. 103:38-41. Zekri, M. and R.C.J. Koo. 1993. A reclaimed water citrus irrigation project. Proc. Fla. State Hort. Soc. 106:30-35. Zekri, M. and R.C.J. Koo. 1994. Treated municipal wastewater for citrus irrigation. J. Plant Nutrition 17(5):693-708. Zekri, M., R.C.J. Koo and L.R. Parsons. 2000. Use of municipal reclaimed water for citrus irrigation. Proc. Interamerican Soc. Tropical Hort. 44:78-84. Zekri, M., L.R. Parsons and R.C.J. Koo. 2000. Irrigation of Florida citrus orchards with reclaimed municipal wastewater. Proc. International Soc. of Citriculture. IX Congr. 1:554-558.

References