耕作模式和滞水时间对稻田中氮磷动态变化的影响研究

通过微区模拟稻田试验,分析了免耕、浅耕和深耕3种耕作模式下滞水时间不同的稻田排水中氮磷的动态特征及总氮、总磷流失潜能,研究了稻田夏季施肥耕作模式和滞水时间对氮磷的减排效能。结果表明：（1）深耕有利于土壤固肥作用的发挥,田面水中TN和NH4＋-N浓度呈逐渐下降的趋势。浅耕和深耕土壤中微生物环境利于硝化反应,不易被土壤吸附的NO3--N得以迅速向田面水中释放。免耕和深耕处理的田面水中TP和DP浓度在第1～5 d内浓度较高,3个耕作处理的滞排水中TP和DP在耕作处理5 d后均处于较低的浓度水平。（2）不同耕作模式滞水5 d后TN的绝对流失量均处于较低水平。免耕、浅耕、深耕在滞水5 d后可分别减少田面水中TN流失59.55%～65.68%、70.15%～88.20%和65.23%～77.26%。深耕处理的模拟稻田田面水中TN的流失潜能相对较小。不同耕作模式处理相对流失形态与潜能以TN为主。（3）免耕处理田面水中TP的绝对流失量最大,浅耕处理田面水中TP绝对流失量最少。免耕、浅耕、深耕在滞水5 d后再排水可分别减少田面水中TP流失54.70%～67.78%、62.99%～85.09%和52.45%～87.99%。浅耕处理模拟稻田田面水中TP的相对流失潜能较小。不同耕作模式处理田面水中磷素的相对流失形态表现出一定的差异性,田面水中磷素流失形态随时间变化呈现出TP与DP交替变化的现象。总之,从减少田面水中氮磷的绝对流失量出发,夏季浅耕不失为最佳清洁耕作模式;同时在滞水5 d后排水,能有效减少田面水中氮磷的流失量,减少稻田排水对面源污染的影响。

Effect of Tillage Models and Water Logging Time on Dynamics of Nitrogen and Phosphorus in Paddy Field

The effects of tillage models and water logging time on dynamics of nitrogen and phosphorus in the paddy field were investigated through microcosm simulation experiments in order to provide the scientific basis for reasonable fertilization and rice high yield.The result showed that the total nitrogen and NH＋4-N in the paddy water gradually decreased with immobilization of fertilizer under the deep plowing condition,and NO-3-N in soil released into the paddy water under shallow plowing and deep plowing condition.Total phosphorus and dissolved phosphorus（DP） in the paddy water were in the higher level from the first to fifth day under the non-farming and deep plowing condition,and in the lower level at the fifth day after tillage.The loss of total nitrogen was 59.55%~65.68%,70.15%~88.20% and 65.23%~77.26%,respectively,at the fifth day after water logging under the tillage models such as non-farming,shallow plowing and deep plowing.The loss of the total phosphorus in the paddy water varied with the tillage models,and 54.70%~67.78%,62.99%~85.09% and 52.45%~87.99%,respectively,at the fifth day after water logging under the non-farming,shallow plowing and deep plowing condition.The loss forms of phosphorus in the paddy water changed with the different tillage models,and exhibited a alterative change between total phosphorus and DP with the water logging time.As loss of nitrogen and phosphorus in the paddy water was concerned,it suggested that shallow plowing should be an optimal and clean tillage model,and meanwhile the drainage at the fifth day after water logging would reduce the loss of nitrogen and phosphorus in the paddy field.