Response of Fresh-market Tomatoes to Nitrogen Fertilizer and Plastic Mulch in a Short Growing Season

Two experiments were conducted on a gravelly loam soil of low N status to determine the amounts and timing of N fertilizer needed for high early and total yields of fresh-market tomatoes grown with or without clear plastic mulch. In both years, the mulch slightly increased early flower number, hastened flower production, and increased early yield. Hastening of maturity of plants on mulch resulted in a 22% increase in ripe fruit in the short (118-day) season of 1984 and a decrease in percent green fruit at final harvest. A N rate of 84 kg·ha −1 increased total yields compared to 0 N, whereas 168 kg·ha −1 of N decreased early yield in 1984 but not 1985. Applying one-half of the N at planting and sidedressing the remaining half was just as effective in increasing yields as applying all the N at planting, even with mulched plants. Low tissue NO 3 -N concentration (< 0.2%) 3 weeks after transplanting reflected insufficient N application for optimum yield but also resulted from limited soil moisture when applied N was adequate. The mulch has increased P consistently and, to a lesser extent, the K concentration in young tomato plants, whereas the effects of mulch on mineral concentration of other elements have varied with year, soil type, and climatic factors.