Estimating Soil Moisture Status in Peach Tree Orchards by Using Crop Water Stress Index

Abstract

Soil moisture content (SMC), in addition to soil water potential, is an important soil index in irrigation application. However, SMC is difficult to determine in field and its estimation can be done by various methods. The objective of this paper is to estimate volumetric soil moisture status by using crop water stress index (CWSI) in a peach orchard for irrigation scheduling. Tree canopy temperature (Tc) was measured by using thermal images in a peach orchard for irrigation scheduling. Tc was investigated in three irrigation regime treatments (factor A) that produced various SMC values, three cardinal points (factor B): South, North and East-West aspects combined, and five up-down vertical position measurements (factor C: upper, middle upper, middle, middle lower and lower) across the tree canopy thermal images. The standard errors of the estimate (SEE) between measured and estimated SMC values range from 1.7 to about 2.2 % of volume. These values essentially show the approximate size of SMC. However, this method can be promising if it is improved by reducing differences between the conditions of determining CWSI and farming conditions. Consequently, the method could be used in orchard region or countries with similar soil and climate conditions.