An evaluation of soil water status using tensiometers in a sandy soil profile under citrus production

Redistribution and depletion of soil water in a Tavares fine sand (Typic Qu artzipsamments) profile were evaluated after irrigation or rain in a commer cial citrus grove with under-tree microsprinkler irrigation. Tensiometers w ere installed at 15-, 30-, 90-, and 150-cm depths in five clusters along th e dripline of 25-year-old Hamlin orange trees on Cleopatra mandarin rootsto ck, Irrigation was scheduled when the soil water potential at the 15- and 3 0-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 responde d to changes in soil water regardless of irrigation or rainfall. Tensiomete r readings at various depths were used to estimate the water content at cor responding 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 dr ained below the rootzone, Results showed some leaching does occur during mo nths 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 manage ment is important to minimize nutrient leaching below the rootzone, tensiom eter-based irrigation scheduling is an important component of nutrient and irrigation best management practices for citrus in sandy soils.