保护性耕作与氮肥后移对巢湖流域麦田磷素流失的影响

农田磷素随地表径流向水体迁移可导致磷肥利用率降低、生产成本上升和环境污染风险增加,源头控制农田磷素流失对于治理巢湖水体富营养化具有重要意义。采用野外定位观测结合室内分析的研究方法,对2009—2010年冬小麦生长期间的径流、泥沙和磷素进行了监测与测定分析,研究了保护性耕作和氮肥后移对巢湖流域麦田P素径流损失及其对环境的影响。结果表明,相对于传统耕作处理（T）,传统耕作＋秸秆还田处理（TS）、氮肥后移处理（NFP）和少免耕＋秸秆还田＋氮肥后移（NTS＋NFP）径流量分别减少了20%、10%和22%,泥沙量分别减少了30%、14%和38%,表现出显著的水土保持作用。各处理径流液总磷（TP）浓度范围是0.095～0.360mg·L-1,其中,颗粒态磷（PP）是磷素随地表径流迁移的主要形式,约占TP的51%～69%。长期的保护性耕作提高径流液中溶解态磷（DP）的浓度,降低了PP的浓度,但TP浓度难以看出明显的变化规律,而氮肥后移降低了径流液中各形态磷的浓度。各处理TP流失量在0.060～0.079kg·hm-2之间,约占当季施磷量的0.2%。处理TS、NFP和NTS＋NFP与处理T相比,TP流失量分别减少了20%、21%和24%。作物生长情况显著影响土壤磷素的流失,地上部分生物量、地上部分吸磷量与径流TP的迁移量呈负相关关系。因此保护性耕作和氮肥后移可以作为源头控制农田磷素流失的较好措施加以推广。

Effects of Conservation Tillage and Postponing N Application on Phosphorous Loss from Wheat Field in Chaohu Lake Region, China

The phosphorous loss via runoff from farmland to waters not only leads to the decline of the P fertilizer use efficiency, but also results in the increasing of farming cost, and the environmental pollution risk. Source control of the P loss from farmland plays an important role in remediation of the eutrophication of Chaohu Lake. The field experiments were carried out from 2009 to 2010 in Chaohu Lake region in order to evaluate the effects of conservation tillage and postponing N application on phosphorous loss via runoff from winter-wheat field and its potential environmental impact. The results showed that, compared with conventional tillage（T）, the runoff from the treatments of conventional tillage＋ straw returning（ TS）, the N fertilization postponed（NFP） and the non-tillage straw returning＋N fertilization postponed（NTS＋NFP）decreased by 20%, 10%and 22%, as well as the sediment by 30%, 14% and 38% respectively, which implied that conservation tillage and postponing N application had significant effects on soil and water conservation. The concentration of total phosphorous（TP） in runoff was in range of 0.095～0.360 mg·L-1, in which the particulate phosphorous（PP）, as the main form of P loss by runoff, accounted for 51%～69%. Although the conservation tillage increased the dissolved phosphorous（DP） concentration, decreased PP concentration, it had no significant influence on the TP concentration in the surface runoff. Postponing N application decreased the concentration of DP, PP and TP in the surface runoff. The phosphorous loads in runoff ranged between 0.060～0.079 kg·hm-2, approximately 0.2% in the total applied phosphorous at the wheat cropping season. The phosphorous loads of TS, NFP and NTS＋NFP declined by 20%, 21% and 24% over T on average. It was also found that the wheat growth affected considerably the loss of phosphorus. There was a negative correlation between the phosphorous loss and the aboveground biomass, or the phosphorous uptakes of wheat. Therefore, the conservation tillage and postponing N fertilization should be popularized for the source control of the phosphorous loss via runoff from wheat field.