不同氮素用量对高肥力稻田水稻-土壤-水体氮素变化及环境影响分析

研究了分次施氮条件下不同氮紊用量对高肥力稻田水稻-土壤-水体含氮量的变化，结果表明：不同施氮水平与植物吸氮置、土壤含氮量以及田面水、渗漏水全氮含量之间具有很强的相关性。但总的来说，氮素利用率不高，有70％～80％左右的化肥氮排入到环境中，对土壤．水体和大气造成污染。在移栽期时，氮紊损失严重。土壤古氮量在水稻生长的前3个时期变化不大，但最终土壤氮素效应明显，低于150kg／hm^2的施氮量不利于土壤肥力的保持。同时用差值法估算出化肥氮对土壤氮的贡献量占化肥氮排入环境量的比例为30％～40％。田面水全氮浓度在每次施肥后第一天达到高峰．一周后全氮浓度显著下降，从环境角度，施肥后一周内是防止田面水氮素流失的主要时期。通过差值法估算的渗漏水中氮含量占化肥氮排入环境氮的比例很小，说明化肥氮当季渗漏淋失的较小。但从总量上却不可忽视，特别是施氮量大于225kg／hm^2时，会对环境造成很大的污染。

N Variation in Rice-Soil-Water System Under Different N Application Level in High-yielding Paddy Field and Its Environment Effect

Research on the variation of nitrogen in the rice-soil-water system under 5 different nitrogen amount treatments and their effects on environment was conducted in Yuhang experimental station of Zhejiang in 2003. The results indicated that the N content in the rice, paddy soil, surface water and leakage water were greatly influenced by different N application amounts. The N use efficiency was low, 70%-80% of fertilizer nitrogen applied were transited into environment. The loss of fertilizer is very high when N applied in rice transplanting time and with high N proportion. The accumulation of soil N content in the paddy is not clear during the first three rice growth stages, but the final effect of the fertilizer on soil N in the last stage is obvious. There is no benefit to soil N if use of nitrogen fertilizer is under 150 kg/hm^2. The proportion of chemical nitrogen contributed to soil N increase account for 30 %-40 % of total chemical N entering the environment amount. The concentration of nitrogen in the surface water reached its maximum value at the first day after N fertilizer applied. The concentration of nitrogen in the surface water was greatly reduced to a CK level after one week, so a week after N fertilizer application is a critical period to avoid the N loss. The chemical N loss is very low through leakage water, but it will pollute water environment after a long time of rice cultivation when the N fertilizer amount exceeds 225 kg/hm^2.