WRSIS系统中稻田田面水和地下排水中氮素的动态变化特征

在江苏高淳县WRSIS系统中进行田间试验,对不同氮肥施用量下稻田田面水和地下排水中氮素动态变化特性进行分析。结果表明:施肥1 d后田面水TN和NH4+-N质量浓度值达到最大,随着时间推移,质量浓度迅速下降,施肥7 d后TN质量浓度下降70%~76%,NH4+-N质量浓度下降83.5%~85.5%。田面水中ρ(NH4+-N)/ρ(TN)和ρ(NO3--N)/ρ(TN)具有相似变化规律,先升后降,且ρ(NH4+-N)/ρ(TN)显著大于ρ(NO3--N)/ρ(TN)。地下排水中氮素以NO3--N为主,施肥后NO3--N质量浓度在3.0~19.0 mg/L的范围内;NH4+-N质量浓度较低,整个生育期质量浓度都在1.1 mg/L以下。田面水和地下排水中氮素质量浓度均随着施肥量的增加而增加。施肥7 d内是防止氮素大量流失的关键时期,需要控制排水;同时减少氮肥施用量能显著减少氮素地表流失和地下渗漏损失量。

Characteristics of dynamic change of nitrogen in surface water and underground drainage water in paddy fields in WRSIS

Field experiments were conducted in the wetland reservoir sub-irrigation system （WRSIS） in Gaochun County, Jiangsu Province, in order to study the characteristics of dynamic change of nitrogen in the surface water and underground drainage water in paddy fields with different amounts of N fertilizer. The results show that the concentrations of TN and NH4^＋ -N in the surface water reached the maximum values one day after fertilization, and decreased rapidly seven days after fertilization by 70% to 76% and 83.5% to 85.5%, respectively. The rates of p（NH4^＋ -N）/ρ（TN） and ρ （NO3^- - N）/ρ （TN） in the surface water had a rising-to-descending trend, and/9（NH4＋ -N）/ρ （TN） was. significantly greater than ρ （NO3^- - N）/ρ （TN）. NO3^- -N was the main form of N in the underground drainage water, and the concentration ranged from 3.0 to 19.0 mg/L after fertilization. The concentration of NH4^＋ -N was very low and its value was lower than 1.1 mg/L throughout the growth period of rice. The concentrations of N both in the surface water and in the underground drainage water increased with the amount of fertilizer. The experimental results show that it is necessary to control drainage within a week after fertilization, which is a crucial period for prevention of large amounts of N loss. Meanwhile, the N loss from the surface runoff and the leakage loss could be significantly reduced by decreasing the use of N fertilizer.