Nitrogen Uptake, Use Efficiency, and Yield in Plasticulture Grown Cabbage

Cabbage is an important specialty crop for Florida with a value at over $70 million. Florida cabbage is traditionally grown on bare-ground using seepage irrigation. In recent years interest in alternative production systems that focus on irrigation water and nitrogen fertilizer conservation has grown. Plasticulture or the use of plastic mulch and drip tape has the potential to reduce irrigation water demand and nitrogen consumption by increasing water and nitrogen use efficiencies (WUE and NUE, respectively). A plasticulture system for Florida cabbage production has been developed and is under assessment for commercial use. Cabbage was grown on 1.23 m wide raised beds with black plastic mulch with drip irrigation. The beds were spaced at 2.03 m with four rows of plants with an in-row spacing of 0.25 m for a total of 77,500 plants/ha. Five nitrogen rates (45, 98, 147, 196, 294 kgN/ha) were tested using a randomized complete block design. Biomass and plant nitrogen uptake were measured bi-weekly throughout the growing season and NUE was calculated. The application of 147, 196 and 294 kgN/ha had similar final biomasses and were significantly greater than the 45 and 98 kgN/ha treatments (P=0.0001). Accordingly, the 45 and 98 kgN/ha treatments had significantly lower marketable yields (>2.1 Mg/ha) than all other treatments (P=0.0001). The 294, 196, and 147 kgN/ha treatments yielded 24.5, 17.2, and 10.4 Mg/ha, respectively and were significantly different from each other. An increase in the N- fertilizer rate applied decreased the apparent NUE. The apparent NUE was 74%, 72%, 58%, and 41% for the n-rate treatments 98, 147, 196, 294 kgN/ha, respectively. The NUE of 196 kgN/ha rate was significantly higher than 294 kgN/ha rate (P=0.001), but marketable yield for the later was 30% higher than the 196 kgN/ha.