ASSESSING EVAPOTRANSPIRATION, BASAL CROP COEFFICIENT, AND IRRIGATION EFFICIENCY IN PRODUCTION PEACH ORCHARD IN CALIFORNIA’S SAN JOAQUIN VALLEY

Accurate field scale observations of crop water use are necessary to maximize crop productivity with limited water resources and to parameterize regional and continental satellite models to estimate near real-time crop water use. However, rapid, continuous observations of field-scale water use in California’s diverse cropping systems have been historically limited. Here we present an integrated framework to assess crop water use in a mature peach orchard in California’s San Joaquin Valley that combines micrometeorological, radiometric, and soil observations. We compared evapotranspiration (ET) measured with an Eddy Covariance tower to soil water balance observations (SM), precipitation (P), and irrigation (I) measurements. Data from our first year of observation indicates a relatively high irrigation efficiency (ET>85% of P+I+ΔSM). Crop coefficient (Kc) had a peak value (~1.2-1.3 of reference ET) that was similar, but more variable than reported for lysimeter-grown peaches in California and which reached an elevated level (Kc>1) earlier in the season. Transpiration (T) was >80% of ET during midday in the growing season. Our preliminary results highlight the need for better quantification of water extraction by mature peach trees from deeper soil layers. Additional observations in the upcoming year from the recently launched Landsat Data Continuity Mission should further enable additional quantification between orchard water use and remotely sensed observations.