稻麦轮作农田系统中氮素渗漏流失的研究

Study on the nitrogen leaching in the paddy-wheat rotation agroecosystem

通过埋设土壤溶液抽滤器采集渗漏水样,对上海郊区大田条件下稻麦轮作系统中土壤氮素(N)的渗漏流失情况进行了观测研究.研究结果表明,稻季渗漏水中总氮(TN)浓度随时间呈下降趋势,其中,硝态氮(NO3--N)由泡田初期的10mg.L-1以上迅速下降至2mg.L-1以下,铵态氮(NH4+-N)则始终低于1.3mg.L-1.施肥能引起渗漏水N素增加;稻田淹水过程也通过改变土壤氧化还原环境控制着N素形态的转换.麦季施肥小区渗漏水中N素形态以NO3--N为主,且施肥后迅速上升到平均7.11mg.L-1;NH4+-N浓度在施肥和不施肥处理中均很低,分别为0.38mg.L-1和0.36mg.L-1.在稻季施肥2.50×104kg.km-2和麦季施肥2.14×104kg.km-2(以N计)的情况下,N素淋失负荷分别为6.08×102kg.km-2和7.42×102kg.km-2,分别占施肥量的2.4%和3.5%;施肥条件下两季总的N素淋失负荷比不施肥处理高出108.7%.

A field case study was conducted to elucidate the dynamic characteristics and the load of N leaching in paddy-wheat rotation fields during one year planting. The results showed that total nitrogen （TN） in natural leaching water declined significantly during the paddy season. Nitrate （ NO3^- -N） fell rapidly at the first several days of immerging, which was from more than 10 mg· L^ -1 to under 2 mg· L^ -1. Ammonia nitrogen （ NH4^＋ -N ） kept at a low level （ 〈 1.3 mg· L^ -1 ）. Flush irrigation, which changed the oxidation-reduction potential of paddy soil, as well as fertilizer application, both had great effect on the N concentration in leaching water. Along with the prolonged flooding, NO3^- -N decreased dramatically and NH4^＋ -N increased slightly. NO3^- -N was the dominant species in wheat season, and it rose quickly after fertilizing （ average 7.11 mg· L^ -1）. NH4^＋ -N concentration was low in wheat season, as in fertilizing plot it was 0.38 mg· L^ -1 , and in control plot was 0.36mg· L^ -1. Under the conditions of an application rate of 2.50 × 10^4 kg· km^ - 2 in paddy season and of 2.14 × 10^4 kg· km^ -2 in wheat season, the N leaching loads were 6.08 × 10^2 kg· km^ -2 and 7.42 × 10^2 kg· km^ -2 separately, and were 2.4% and 3.5% of total fertilizer application. In one year planting, the N leaching load in fertilizing plot was 108.7% higher than in control plot.