Yield, Evapotranspiration, Production Functions, Crop Coefficients, Water Productivity and Soil‐Water Extraction of Three Watermelon Varieties

ABSTRACT While watermelon is an important commodity in the United States and worldwide, some of the fundamental watermelon productivity indices (crop evapotranspiration [ ET c ], transpiration [ T r ], evaporation [ E ], ET ‐yield production functions [ ETYPF ], basal crop coefficients [ K cb ], crop water productivity [ CWP ], soil‐water extraction [ SWE ]) have not been quantified. These variables were quantified for three different watermelon varieties (Quetzali, Sangria and Top Gun) in two seasons. The 2‐year average yields were 34,061, 27,967 and 26,046 kg/ha for Sangria, Top Gun and Quetzali, respectively. All yields were significantly different ( p < 0.05) from each other. The seasonal total ET c was 524 and 457 mm, T r was 381 and 321 mm and E was 146 and 140 mm in 2015 and 2016, respectively. The two‐season average K cb values were 0.40, 0.53, 0.94, 0.93, 0.63 and 0.40 for planting–germination, germination–vegetative, vegetative–flowering, flowering–fruit initiation, fruit initiation–fruit growth and fruit growth–ripening stages, respectively. The ETYPF was linear and strong (slope = 0.299; R 2 = 0.90). The two‐season average CWP was 6.5, 8.0 and 6.9 kg/m 3 for Quetzali, Sangria and Top Gun, respectively. It can be expected that 55%–57% of the seasonal total watermelon SWE will occur in the 0‐ to 60‐m soil layer and 77%–81% will occur in the 0‐ to 120‐cm soil layer.