Abstract Lee JohnsonMichael CahnForrest Melton

CropManage Application for Vineyard Irrigation Decision Support

Lee Johnson,* Michael Cahn, and Forrest Melton
*CSU Monterey Bay, Dept Applied Environmental Science, 100 Campus Center, Seaside, CA, 93955 (lee.f.johnson@nasa.gov)

CropManage is a free web application developed by U.C. Cooperative Extension to support evapotranspiration-based irrigation scheduling and nutrient management for major specialty crops. Prescribed phenology curves are used to develop daily estimates of canopy cover within a given field, based on days since planting (annual crops) or budbreak (trees, vines). These curves are modulated by a MaxCan param­eter representing seasonal maximum canopy cover. Crop development observa­tions can be used to adjust for factors such as weather anomalies or non-standard agronomic practices, as needed. Canopy cover is converted to crop coefficient and combined with reference evapotranspiration to derive daily water consumption. Guid­ance on crop water requirement is then conveyed to users in terms of system runtime issued on-demand for a given date, largely based on total evapotranspiration since last irrigation event. In this study, CropManage was adapted to vineyards by adding modules accounting for early-season soil moisture depletion and cover crop pres­ence. A crop stress parameter was added to accommodate deficit irrigation practice, allowing the user to specify percentage departure from full water requirement along with start/stop dates. An initial verification exercise was performed in three wine­grape vineyards located in California’s Central Coast (2020), North Coast (2020), and Central Valley (2019). Daily crop evapotranspiration was monitored by eddy-covari­ance fluxtowers. MaxCan was measured by ground and satellite observation. Stress regime was specified by grower practice, where available; otherwise, stress levels were inferred from applied water records. Mean absolute error and mean bias error of modeled cumulative evapotranspiration were computed with respect to the eddy covariance measurements collected throughout the growing season. Results indicate the modified CropManage water management module performs reasonably well for winegrape. Additional effort is planned to modify the nutrient module for vineyard use.

Funding Support: California Dept Food & Agriculture, Specialty Crop Block Grant Program