控制淋洗条件下土壤-花椰菜体系无机氮动态及平衡

在北京郊区中壤质潮土上设置田间试验。结果表明:花椰菜获最大产量的氮供应量为300kghm-2。生育期花椰菜主要吸收表层(0～30cm)土壤中的无机氮,对下层(30～60cm)土壤无机氮(Nmin)的利用随氮供应量的增加而减少。不同生育期0～60cm土层中无机氮(Nmin)含量均随氮供应量增加而增加,但施肥后土壤中最高无机氮(Nmin)含量出现的时间随氮供应量增加而延迟。花椰菜生育期土壤有机氮矿化速率随生长期延长而增加,平均达N1.3kghm-2d-1,相当于各处理总吸氮量的47.5%～89.2%。试验后0～30cm及30～60cm土层无机氮(Nmin)含量随氮供应量增加而明显增加,但60～90cm土层无机氮(Nmin)受氮供应的影响不明显。花椰菜当季氮肥利用率及氮素利用率随施氮量增加而降低,最佳产量时的氮肥利用率及氮素利用率分别为36.5%和50.8%。土壤-花椰菜体系氮素表观损失量随氮施用水平的增加而明显增加,但其占总氮供应(肥料氮+播前土壤氮)的比例受氮供应的影响不明显,大致为20%。

Inorganic N Dynamics and Balance in Cauliflower- soil Sysem under Non- Leaching Field Condition

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.