A NEW TECHNIQUE FOR CONTINUOUS MONITORING OF SOIL MOISTURE CONTENT TO IMPROVE CITRUS IRRIGATION

ALVA, A. K.

Abstract


Although a number of techniques are available to schedule citrus irrigation, continuous monitoring of soil moisture within and below the depth of rooting is important to determine: (i) the depletion of soil moisture below the acceptable limit within the rooting depth, and (ii) the duration of irrigation to replenish the soil moisture deficit within the rootzone while minimizing leaching below the rootzone. EnviroSCAN sensors (which work on the principle of dielectric constant of air, water, and soil) can be installed at any required depth under the canopy in the zone of maximum root activity. Using the calibration, these sensors measure the soil moisture content at the depth of installation and can be integrated for the entire depth of rooting. The sensor readings respond to moisture redistribution due to gravity and depletion due to root uptake. The depth integrated soil moisture content (for depth of rooting), on a given date, can be compared with the recommended: (i) full point, i.e., the maximum water content that can be stored at that depth with minimum leaching, and (ii) refill point, i.e., the water content at allowable depletion of available soil moisture (ASM) such as either N or O depletion of ASM. Once the set points are established, the subsequent irrigation scheduling can be managed precisely and conveniently by downloading the sensor data at frequent interval. The sensor below the rooting depth provides the changes in soil moisture content at this depth as an indication of leaching below the rootzone, thus, is the basis to fine tune irrigation scheduling to minimize leaching below the rootzone.

Keywords


citrus; irrigation scheduling; capacitance probe; water content; sandy soils; available soil moisture

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283