Under non-leaching field condition, the effects of N rate on N utilization of
cauliflower on soil
inorganic N dynamics and
balance were studied. The results showed that nitrogen rate for the maximum yield was 300 (kg N hm~(-2)) minus Nmin in 0-60cm soil layer before transplanting. The absorption of soil N by
cauliflower was mainly from 0-30 cm soil layer, while the absorptionof N from 30-60cm soil layer decreased with the increasing of N rate. Inorganic N content in 0-60 cm soil
increased with the increase of N supply at different stages, but the appearance date of the maximum inorganic N content in 0-60 cm soil layer was delayed by higher urea supplying. The inorganic N from soil organic nitrogen mineralization was about 47.5-89.2%,and total aboveground N and soil N mineralization rate increased with the prolonged growth. Soil inorganic N (Nmin) residuals in 0-30 cm and 30-60 cm soil layers at harvest increased with the increase of N supply, while inorganic N residuals in 60-90 cm soil layers were not significantly affected by N supply. Both N fertilizer use efficiency and nitrogen use efficiency increased with N rate, and in the optimum nitrogen treatments the nitrogen fertilizer use efficiency and nitrogen use efficiency were 36.5% and 50.8%, respectively. During the experiment, the amount of apparent N loss increased with the increasing of N supply, but the percentage of N loss to total N supply was about 20% of N supply and was not affected significantly by N supply levels.