Submitted to: International Society of Citriculture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/1999
Publication Date: 12/1/2000
Citation: FARES, A., OBREZA, T.A., ALVA, A.K. USING MODERN IRRIGATION SCHEDULING TECHNIQUES TO KEEP SOIL-APPLIED CHEMICALS IN THE ROOTZONE. INTERNATIONAL SOCIETY OF CITRICULTURE PROCEEDINGS, p. 65. 2000. Interpretive Summary:
Technical Abstract: Knowledge of soil water status is important to properly manage soil and water resources. Accurate irrigation management requires methods of assessing both water application quantity and timing in order to avoid crop water deficits. EnviroSCAN and Diviner 2000 (Sentek, Adelaide, South Australia), fixed and handheld portable capacitance soil water monitoring devices, respectively, have been used to measure real time in situ soil water content for different crops around the world. EnviroSCAN has been used for citrus irrigation management since 1995 to help prevent leaching of nitrogen fertilizer. Soil moisture monitored at 10, 20, 40, 70, and 110 cm depths below the soil surface with the EnviroSCAN compared favorably with those determined gravimetrically. A soil water balance approach at the field level was used to process water content data, combined with irrigation and rain data, to calculate evapotranspiration (ET) and water losses below the rootzone on a daily, monthly, and annual basis. Calculated daily ET rates showed strong seasonal patterns and varied from less than 0.4 mm/d in Jan to 5 mm/d in July and Aug. Annual ET in 1997 was approximately 947 mm, which was equivalent to 53 percent of the total water input. The cumulative annual drainage in 1997 was 890 mm which accounted for 47 percent of the total water input (irrigation and rainfall) into the system. Diurnal variation in temperature marginally influenced the soil moisture measurements by EnviroSCAN. However this effect was negligible as compared to the variation due to soil spatial variability. The EnviroSCAN capacitance probe is a practical tool that can be used by growers and researchers for citrus irrigation scheduling, and for plant water use and chemical leaching studies.