耕作措施对坡耕地红壤地表径流氮磷流失的影响

Effects of Tillage Measures on Nitrogen and Phosphorus Loss from Surface Runoff in Red Soil on Slope Farmland

云南山地面积约占全省土地总面积的94%,特殊的地形特征,极易引发坡面土壤侵蚀和养分流失,严重影响了农业可持续生产。采取有效的农艺措施来减少坡耕地土壤养分流失是十分有必要的。为此,通过4年定位试验对顺坡(2组处理)、横坡(2组处理)2种耕作方向的复合农艺措施处理进行研究。结果表明:云南坡地红壤的径流时间主要集中在6-9月,且产流雨量占年降雨量的65.62%~75.82%。产流雨量与年降雨量呈现一致趋势。径流量和产流雨量呈线性关系(RNVF^2 =0.5977,ROVF^2 =0.4151,ROHF^2 =0.3782,ROHFR^2 =0.3355),其相关性大小顺序为顺坡处理>横坡处理,不施肥处理>施肥处理,覆膜处理>揭膜处理(P<0.01)。大雨(25~49.9 mm)和暴雨(≥50 mm)造成了年度大部分径流和养分的流失。横坡垄作组处理产生地表径流(177.13±28.87)^(182.28±33.75)mm,径流中总氮流失量(7.66±2.51)^(7.85±1.92)kg/hm^2,总磷流失量为(0.91±0.26)^(1.09±0.27)kg/hm^2,与顺坡垄作OVF(常规处理)相比径流和养分极显著减少了49.57%~52.13%,33.16%~53.88%(P<0.01)。不同耕作措施下,复合耕作模式(优化施肥+横坡垄作+旺长期揭膜)拦截径流和养分流失的效果最好。RDA分析结果发现,与降雨量相比较,径流量是影响氮磷养分变化的主要环境因子(P<0.01)。径流量与氮养分(NH 4^+-N除外)流失量的相关性高于与磷的相关性,表明氮比磷更容易随径流流失。顺坡处理NVF和OVF与环境因子径流量和氮磷养分流失量TN、TDN、NO 3^--N、NH 4^+-N、TP、TDP呈正相关,横坡处理OHF和OHFR与其呈负相关。

Mountainous area accounts for about 94%total land area of Yunnan province.The special topographical characteristics can easily cause slope soil erosion and nutrient loss,which seriously affects agricultural sustainable production.It is necessary to take effective agronomic measures to reduce soil nutrient loss in sloping land.Based on the 4-year experiment,compound agronomic measures for two tillage directions,vertical ridge(VR)group(2 treatments)and horizontal ridge(HR)group(2 treatments)were in location monitoring.Results showed that runoff generation time of red soil on slope land in Yunnan was mainly from June to September,and the rainfall of producing runoff accounted for 65.62%~75.82%of the annual precipitation.The rainfall of producing runoff had same trend with annual precipitation.The relationship between rainfall of producing runoff and runoff depth were linear(RNVF^2 =0.5977,ROVF^2 =0.4151,ROHF^2 =0.3782,ROHFR^2 =0.3355).The correlation order was that vertical ridge(VR)group was greater than horizontal ridge(HR)group,non-fertilizer application treatment was greater than fertilizer application treatment,and mulching treatment was greater than the mulching removal treatment(P<0.01).Heavy rain and rainstorm caused most of the annual runoff and nutrient loss.Surface runoff produced by HR tillage was(177.13±28.87)to(182.28±33.75)mm,TN(7.66±2.51)to(7.85±1.92)kg/hm^2,TP(0.91±0.26)to(1.09±0.27)kg/hm^2.Average reduction rate(ARR,%)of runoff and nutrients were 49.57%to 52.13%and 33.16%to 53.88%significantly,compared with conventional treatment(OVF)of VR tillage group(P<0.01).Under different tillage measures,OHFR had best effect of intercepting runoff and nutrient losses.The results of RDA analysis show that compared with rainfall,runoff was the main environmental factor affecting the change of nitrogen and phosphorus nutrient(P<0.01).The correlation between runoff and the nitrogen nutrient loss(except NH 4^+-N)was higher than that of phosphorus,which indicating nitrogen was more easily loss with runoff than phosphorus.NVF and OVF treatments of vertical ridge(VR)group were positively correlation with environmental factor runoff and nutrient losses of TN、TDN、NO3^--N、NH 4^+-N、TP、TDP,while OHF and OHFR treatments of horizontal ridge(HR)group were negatively correlation with it.