RESUMO
A field experiment was conducted to study the effects of different nitrogen forms ((NH2)2CO-N, NO(3-)-N, NH(4+)-N, and NO(3-)-NH4+) and their ratios on the yield formation, quality, and nutrient (N, P, and K) absorption of broccoli (Brassica oleracea). Fertilization with NO(3-)-N increased the accumulation of nitrate and soluble sugars in ball flower. When the NO(3-)-N: NH(4+)-N ratio was ranged from 3:7 to 5:5 and from 5:5 to 7:3, respectively, the accumulation of nitrate in the ball flower was reduced, while the soluble sugars content was promoted. Fertilization with (NH2)2CO-N and NH(4+)-N was conducive to the improvement of Vc content in the ball flower. N fertilization increased the accumulation of N, P, and K in plants, with the highest contents of N, P, and K observed at rosette stage. Throughout the entire growth period, NH(4+)-N fertilization improved the plant N content, whereas NO(3-)-N fertilization improved the plant K content. At different growth stages, the effects of different N sources on plant P content varied. As compared with applying single N forms, the NO(3-)-N:NH(4+)-N ratio ranged from 3:7 to 5:5 could improve the yield significantly. It was suggested that a combined application of NO(3-)-N and NH(4+)-N with an appropriate ratio could improve the productivity, quality, and economic return of broccoli.