Effects of Irrigation with Reclaimed Municipal Wastewater On Citrus Trees.

Water 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.  Reclaimed municipal wastewater was evaluated on citrus trees in central Florida for over six years.  The effects of irrigation with reclaimed water on soil water content, soil chemical analysis, leaf mineral status, and fruit quality were compared with those of irrigation with well water.  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 toxicity levels.  Overall, blocks irrigated with reclaimed water had trees with denser canopies, 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, possibly due to higher application rates with reclaimed water.  This highly treated wastewater in central Florida has been found to be a safe and good option for increasing water supplies, but not a significant source of plant nutrients to citrus trees.