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Title: WATER RELATIONS, FRUIT QUALITY AND YIELD OF CITRUS UNDER DIFFERENT IRRIGATION & FERTILIZATION RATES IN A SANDY SOIL

Author
item FARES, A - UNIV OF FLORIDA
item Alva, Ashok

Submitted to: Dahlia Greidinger International Symposium Nutrient Management under Salinit
Publication Type: Proceedings
Publication Acceptance Date: 6/1/1999
Publication Date: 12/5/2000
Citation: Fares, A., Alva, A.K. 2000. Water relations, fruit quality and yield of citrus under different irrigation & fertilization rates in a sandy soil. Dahlia Greidinger International Symposium Nutrient Management under Salinit.

Interpretive Summary: Optimization of irrigation is critical to improve water uptake efficiency and minimize leaching losses. This is quite critical under fertigation to ensure that leaching of nutrients below the rootzone is minimized. Continuous measurement of soil water content within and below the rooting depth soil allows an evaluation of the water being leached below the rooting depth. This study was conducted in 4-year old Hamlin orange trees in a Candler fine sandy soil with three irrigation regimes and two N rates as fertigation (134 and 190 kg/ha). Different irrigation regimes were created by changing the wetting area into 1.8, 7.6, or 16.3 m2/tree with sprinkler delivery rate of 50 liter/hour. The medium irrigation regime produced the optimal yield. The yields decreased 23 to 24 percent with the high or low irrigation regimes. With high irrigation rate, excessive leaching of water and nutrients below the rootzone may have caused the yield reduction. In contrast, with low irrigation rate, due to increased surface area, coverage appeared to contribute to a reduction in yield.

Technical Abstract: The effects of three irrigation rates (high, medium, and low) and two fertigation rates (for target N rates of 134 and 190 kg ha-1 using a liquid fertilizer blend containing 6:2.3:10.5 ratio of N:P:K) on the water use, growth, yield and juice quality of 4-year-old "Hamlin" orange trees (Citrus sinensis (L.) Osb.) on Swingle citrumelo (Citrus paradisi Macf. X Poncirus trifoliata (L.) Raf.) rootstock planted in a Candler fine sand (hypertherm uncoated Typic Quartzipsamments) have been evaluated. Capacitance probes were used to monitor the soil moisture content under the tree canopy near t dripline position with sensors placed at 10, 20, 40, 70, and 110 cm depth. Continuous monitoring of the soil moisture through the soil profile was use to schedule irrigation at either 33% or 66% depletion of the available soil moisture content in the root zone during February to May, and June to January, respectively. The juice acidity was lower for the high irrigation ntreatment than that for the medium and low irrigation treatments. Increas the N rate decreased the juice acidity. The brix:acid ratio increased with increasing irrigation rates. Irrigation rates did not influence the juice brix content. The fruit yield with the medium irrigation treatment was 23 and 24% greater than that at the low and high irrigation treatments, respectively. Fruit yield was 14% greater than that at the low and high irrigation treatments, respectively. Fruit yield was 14% greater at the hi N rate than that at the low N rate. More water was leached below the root zone with the high irrigation treatment than the other treatment during the dry season. However, evapotranspiration (ET) was greater at the medium irrigation treatment than the other two treatments.