Real-time Drip-irrigation Scheduling of Watermelon Grown with Plasticulture

A two-year study was conducted in North Florida on a fine-sandy soil, to develop and test a crop factor for watermelons (Citrullus lanatus Thunb.) grown with plasticulture and daily drip-irrigation. Crop water use was calculated daily by multiplying Class A pan evaporation (Ep) with the proposed crop factor values 0.20, 0.40, 0.70, 0.90, and 0.70 for period 1-2, 3-4, 5-8, 9-11, and 12-13 weeks after transplanting, respectively. `Mardi Gras' watermelons were established in a factorial combinations of 126, 168 and 210 kg/ha of N and 33%, 66%, 100% and 133% of the reference irrigation rate. The effect of N rate and the interaction irrigation x N rate were not significant on total marketable yield, individual fruit weight and total soluble solids. Watermelon yield responded quadratically to irrigation rate for both years. The results suggest that the highest watermelon yields would be achieved with a combination of 168 kg/ha of N and irrigation scheduled in real-time using daily Class A pan evaporation values multiplied by crop factor values of 0.24, 0.48, 0.84, 1.08, and 0.84 for period 1-2, 3-4, 5-11, 12, and 13 weeks after transplanting, respectively, which corresponded to the seasonal irrigation amounts of 450 and 343 mm in 2001 and 2002, respectively.