RESPONSE OF CHINESE-CABBAGE TO NITROGEN RATE AND SOURCE IN SEQUENTIALPLANTINGS

''Tropical Quick' Chinese cabbage (Brassica rapa L., Pekinensis Group) was planted three times at 2-week intervals in Spring 1991 (direct-se eded) and two times in Fall 1991 (transplanted) in double rows on poly ethylene-mulched beds to evaluate N source and rates. Calcium nitrate, ammonium nitrate, urea, urea-ammonium nitrate solution (Uran), and ur ea-calcium solution (Nitro-Plus) were applied preplant at 67,112, and 157 kg N/ha. The two later spring planting dates, compared with the ea rliest date, resulted in greater head fresh weights and higher insect damage incidence, but lower tipburn and flowering incidence. The earli er fall planting resulted in greater head fresh weight but a much high er flowering incidence than the later planting. Irrespective of planti ng date, head fresh weight increased quadratically, and tipburn and fl owering incidence decreased linearly with increasing N rate. Although N source affected head fresh weight and tipburn incidence, differences were too small to be of practical value.