Lee Johnson,* Michael Cahn, Ryan Solymar, Adam Purdy, David Chambers, Noe
Cabrera, George Zhuang, and Forrest Melton
*CSUMB/NASA-ARC CREST, Dept. of Applied Environmental Science, 100 Campus
Center, Seaside, CA, 93955 (lee.f.johnson@nasa.gov)

Two publicly available applications relevant to vineyard irrigation management are described. OpenET is a satellite-based system that applies an ensemble of remote sensing methods to enable wide-area monitoring of evapotranspiration (ET) and related measures such as vegetation canopy development (via the NDVI spectral index). Data are freely available at one-quarter acre spatial resolution and may be automatically aggregated to the individual block level. The satellite-based daily ET data were compared with in-situ eddy covariance measurements collected by micro-meteorological instrumentation in a Central Coast vineyard over a three-year period (2020 to 2022). Estimate uncertainties were reasonably consistent with prior reports for GRAPEX sites in the Central Valley and North Coast. The CropManage (CM) web application is a free software tool developed and operated by UC Cooperative Extension for ET-based irrigation scheduling of major specialty crops. CM provides specific guidance for irrigation events as irrigation system runtime. Applied water recommendations are based largely on estimated ET, derived from assumed canopy cover and associated crop coefficients, since the last irrigation or rainfall event. The application was recently adapted to vineyards by accounting for the presence of a winter/spring cover crop, and for vine water stress imposed by regulated deficit irrigation. A 2022 field campaign involved 12 Central Coast and San Joaquin Valley commercial vineyards, and OpenET data were used to help evaluate CM output. Maximum percent vine cover was compared to estimates derived from average July satellite NDVI. The difference for 10 sites lacking midseason groundcover ranged from 0 to 7% between data sets, with average agreement near 4%. Cumulative ET estimates agreed with OpenET to within 12% at most sites, while larger discrepancies at the remaining sites may require additional data collection and analysis during the 2023 season. Satellite-based systems such as OpenET have the potential to help parameterize CropManage and similar agricultural decision support systems.

Funding Support: CA Dept. Food & Agriculture