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Paramasivam, S.2; Alva, A. K.3; Fares, A.2

Technical Articles

Redistribution and depletion of soil water in a Tavares fine sand (Typic Quartzipsamments) profile were evaluated after irrigation or rain in a commercial citrus grove with under-tree microsprinkler irrigation. Tensiometers were installed at 15-, 30-, 90-, and 150-cm depths in five clusters along the dripline of 25-year-old Hamlin orange trees on Cleopatra mandarin rootstock. Irrigation was scheduled when the soil water potential at the 15- and 30-cm depths exceeded either −10 KPa (Jan. to June) or −15 KPa (July to Dec.) to replenish the water deficit (below field capacity) in the top 90 cm of the soil profile. The tensiometers placed at 15- and 30-cm depths responded to changes in soil water regardless of irrigation or rainfall. Tensiometer readings at various depths were used to estimate the water content at corresponding depths using the van Genuchten analytical relationship equations. Total soil water contents within the rootzone (0 to 90 cm) and below the rootzone (90 to 150 cm) within the monitoring depth (0 to 150 cm) were also calculated to estimate the water available for the trees and water that drained below the rootzone. Results showed some leaching does occur during months when there is heavy rainfall. This study demonstrated that tensiometer readings can be used to calculate the soil water content at various depths within the soil profile. Therefore, duration of irrigation can be adjusted to minimize leaching below the rootzone. Because optimal irrigation management is important to minimize nutrient leaching below the rootzone, tensiometer-based irrigation scheduling is an important component of nutrient and irrigation best management practices for citrus in sandy soils.

1Florida Agricultural Experiment Stations Journal Series No. R-06070.

2Postdoctoral Research Associates. University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850. Dr. Paramasivam is corresponding author. Email:

3Research Leader, USDA-ARS-PWA, 24106 North Bunn Road, Prosser, WA 99350.

Received June 7, 1999; accepted Dec. 2, 1999.

© 2000 Lippincott Williams & Wilkins, Inc.