Soil water components based on capacitance probes in a sandy soil

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Soil Science Society of America Journal


Understanding soil water movement is needed to manage irrigation to minimize water drainage, nutrient leaching below the root zone, and contamination of groundwater. We hypothesized that soil water content determined by capacitance probes can be used for irrigation scheduling and estimating soil water components. Objectives of this study were (i) to evaluate the performance of capacitance probes for optimizing irrigation management for 'Hamlin' orange trees [Citrus sinensis (L.) Osb.] on Swingle citrumelo [Citrus paradisi Macf. x Poncirus trifoliata (L.) Raf.] rootstock on a Candler Free sand soil (hyperthermic, uncoated, Typic Quartzipsamment) in Central Florida and (ii) to determine soil water balance components. Irrigation levels were determined based on available soil water (ASW) and tree growth stage. The soil water data measured at finite time interval by capacitance probes were used with irrigation and rainfall data to calculate daily evapotranspiration (ET) and drainage rates. Daily ET rates showed strong seasonal patterns and varied from <0.4 mm d-1 in January to 5 mm d-1 in July and August. The annual ET in 1997 was 920 mm or 53% of the total water input (irrigation and rainfall). The cumulative annual drainage in 1997 was 890 mm, or 47% of the total water input. Furthermore, 82% of the cumulative annual drainage was contributed by rainfall. Irrigation based on monitoring soil water content using capacitance probes minimized water drainage below the root zone in a system where rainfall contributed substantially to drainage.

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