Water Use Dynamics of Peach Trees under Postharvest Deficit Irrigation

Abstract

Postharvest deficit irrigation is a potential strategy for conserving valuable fresh water for production of early season tree fruit crops such as peaches. However, water use dynamics under deficit irrigation conditions that can be described as seasonal changes in crop evapotranspiration (ET c ) and crop coefficient (K c ) are largely unknown. A three-year field study was carried out in a 1.6 ha peach orchard to determine seasonal ET c and K c characteristics. The orchard was divided equally into 72 plots, in which 12 randomly selected plots received deficit irrigation and the remaining 60 plots received full irrigation. A Bowen ratio flux tower was installed in the orchard to make meteorological measurements for estimating an integrated ET c for the orchard. The study showed that from July to August 75-85% of the daily net radiation was used by latent heat or partitioned into ET c . The average monthly cumulative ET c was 151 mm in June, 162 mm in July, and 155 mm in August. K c values under deficit irrigation conditions or termed as Deficit_K c was computed as ratios of the ET c over potential evapotranspiration or ET o , and were compared with K c derived from a lysimeter study under non-water stressed conditions or termed as Lysimeter_K c . The maximum Deficit_K c values were 0.90, 1.03, and 1.07 for the three field seasons but all were smaller than 1.20, the maximum Lysimeter_K c . The study demonstrated that water stress under deficit irrigation can be characterized in K c values. The approach may be used to detect if portions of an orchard or the entire orchard are under water stress. Conversely, the method may provide guidance on deploying deficit irrigation practices with pre-determined Deficit_K c .

Model Based Study of Crop Evapotranspiration under Canopy Shading

“…The trees are spaced 1.8 m apart between the rows and 4.9 m within a row. The whole orchard is equally divided into 72 irrigation plots with each plot consisting of 24 trees in three rows with eight trees per row [2].…”

“…California has the highest agricultural production in the United States with total revenues exceeding $47 billion [1]. The climate and soil are favorable for growing crops but scarcity of annual rainfall is leading to severe droughts, affecting the crop yield, and hampering the local economic development [2,3]. While advanced irrigation technology has somewhat alleviated the situation, frequently occurring drought events may still lead to shortage in irrigation water.…”