Watermelons are another minor crop produced in the lower Colorado River Region, near Yuma, and other parts of Arizona during the spring and early summer period. In the Yuma area, production typically follows fall-winter leafy vegetables. In 2023, 4,100 acres of watermelons in Arizona had a value of approximately 1.7 million dollars.  Watermelons were once produced by furrow irrigation, but now they are largely produced with buried drip irrigation and plastic mulch due to significant production advantages. Using eddy covariance (Figure 1), we have measured seasonal ETc ranging from 371.4 to 471.3 (14.6 to 17 acre-inches) for watermelon produced in drip/plastic mulch systems. The growth periods as tracked by growing degree days (GDD) and satellite derived normalized vegetable indices (NDVI) and crop coefficients for each period are shown in Table 1. Irrigation application efficiencies are high in drip irrigated watermelons and surface soil salinity typically increased over the increase that already occurred in the fall-winter crop. Pre-irrigation is usually required to restore salt balance before fall vegetable production.

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