Optimizing the Nitrogen Fertilizer Application Rate for Plasticulture Grown Cabbage in Florida.

Florida ranks third in U.S. cabbage production and the majority of cabbage producing areas dominated by seepage irrigation. Prior studies have demonstrated that with the use of plasticulture, higher plant populations can be achieved. The focus of this study was to evaluate the effect of irrigation and N application rates on plasticulture grown cabbage. Cabbage var. Bravo was grown on 48-inch wide raised beds with black plastic mulch and drip irrigation. Irrigation vs. N-rate treatments were arranged in a split plot design with four replications. Two irrigation regimes, 100% ETc and soil moisture sensor (SMS) controlled were assigned to main plots. The soil moisture sensor was set to the soil field capacity and it bypassed irrigation events when the soil moisture was above the desired threshold. The N-rates tested were 44, 88, 131, 175, 263 lb/a. The SMS reduced irrigation application by 22%. There was no interaction between irrigation and N-rates for yield. There was a positive linear response in marketable cabbage yield to increased nitrogen application rates, suggesting that an optimum rate was not reached. Cabbage grown at 263 lb-N/a produced 52,800 lb/a and had significantly greater yields than all other N-rates (P<0.001). The N-rate of 175 lb/a yielded 37,214 lb/a. Yield was higher for N-rates of 88 and 131 lb-N/a under SMS treatment compared to ETc treatment, suggesting that irrigation management increased soil nitrogen availability in the root zone when nitrogen was supplied in limited quantities.