氮磷减量对棉花—油菜轮作系统作物产量及氮、磷流失的影响

长期不合理施用化肥导致土壤酸化、大气污染等一系列环境问题，化肥合理减施将有利于提高肥料利用率、促进耕地健康发展。本试验采用田间试验，以常规施肥（棉花季N：390 kg/hm2，P2O5：105 kg/hm2；油菜季N：180 kg/hm2，P2O5：54 kg/hm2）为对照，研究洞庭湖区域旱地棉花—油菜轮作下氮磷肥减量（10%、20%、30%）对作物产量及氮磷养分流失的影响。结果表明：与常规施肥相比，氮磷肥减量10%、20%对作物产量影响不显著，但明显提高肥料利用率，显著减少旱地氮磷径流损失；养分流失以棉花季为主，且棉花花铃期为关键时期。氮磷肥减量20%处理氮、磷肥利用率较常规施肥处理分别提高了5.41、12.23个百分点（棉花季）和10.91、11.91个百分点（油菜季）；氮磷肥减量处理总氮、总磷流失量分别为0.69～5.48 kg/hm2、0.08～0.24 kg/hm2（棉花季）和0.17～0.34 kg/hm2、0.05～0.11 kg/hm2（油菜季），较常规施肥处理分别降低了5.94%～31.20%、12.80%～44.02%（棉花季）和18.88%～37.61%、10.18%～24.85%（油菜季）。综上，在本研究所设肥料减量范围内，氮磷肥减量20%处理能稳定作物产量、提高肥料利用率，降低氮磷流失。

Effects of reducing nitrogen and phosphorus application on crop yield and nitrogen and phosphorus loss of cotton-rapeseed rotation system

A series of environmental problems such as soil acidification and air pollution were caused by long-term unreasonable fertilization. Reasonable reduction of chemical fertilizer application will be conducive to improving the utilization rate of fertilizer and promoting the healthy development of cultivated land. Taking conventional fertilization (cotton season N: 390 kg/hm2, P2O5: 105 kg/hm2; rapeseed season N: 180 kg/hm2, P2O5: 54 kg/hm2) as the control (T1), a field experiment was conducted to determine the effects of N and P fertilizer reduction (10%, 20%, 30%) on crop yields, runoff N and P loss, in a cotton-rapeseed rotation field in Dongting Lake area. The results indicated that compared with the control, the treatments with reduction of N and P fertilizer by 10% and 20% (T2 and T3) had little impact on crop yield, but significantly improved the utilization rate of N and P fertilizer. Meanwhile, the N and P runoff loss were also significantly reduced in dry land. In cotton-rapeseed rotation, nutrient loss was mainly appear in cotton season, and the key stage was flower bell period. Simultaneously, compared to the control, the N and P fertilizer utilization rates of 20% N and P fertilizer reduction treatment were increased by 5.41%, 12.23% (cotton season) and 10.91%, 11.91% (rapeseed season), respectively. The TN and TP loss of the N and P fertilizer reduction treatments were 0.69~5.48 kg/hm2, 0.08~0.24 kg/hm2(cotton season) and 0.17~0.34 kg/hm2, 0.05~0.11 kg/hm2 (rapeseed season) respectively, which were decreased by 5.94%~31.20%, 12.80%~44.02%(cotton season) and 18.88%~37.61%, 10.18%~24.85% (rapeseed season), compared with the conventional fertilization treatment. To sum up, within the scopes of fertilization reduction rates in this study, the reduction of N and P fertilizer by 20% can maintain a stable crop yield, and improve fertilizer utilization rate, while reduce N and P loss.