三种牧草对三峡库区旱坡地氮磷养分流失的影响

本研究以三峡库区王家沟小流域为对象,通过田间试验和室内分析相结合的方法,以种植常规玉米为对照(T₁),利用2015年5-8月自然降雨采集的地表径流样品,研究了黑麦草(T₂)、墨西哥玉米草(T₃)、大力士甜高粱(T₄)三种牧草对三峡库区旱坡地氮磷流失的影响,为三峡库区种植结构调整及面源污染防治提供科学依据。结果表明,3种牧草均能显著减少径流及泥沙中的氮磷养分流失量,以墨西哥玉米草效果最佳;降雨造成的氮磷养分流失以泥沙为载体为主要流失途径,占总氮、总磷流失量的76.34%~79.97%和81.69%~83.90%;黑麦草、墨西哥玉米草的生物量及干物质积累量最高,分别为玉米处理的4.45、1.52倍和4.89、1.53倍,种植4种植被的养分截存效果表现为T₂、T₃>T₄>T₁。考虑到养分截存效果及饲用经济效益,三峡库区旱坡地应优先选择种植墨西哥玉米草,其次选择黑麦草,代替传统的玉米种植模式。

Effects forages on nitrogen and phosphorus loss from sloping land draining into the Three Gorges Reservoir

The research was conducted in a small catchment,Wangjiagou,draining into the Three Gorges Reservoir.We combined field experiments and laboratory analysis;corn was used as the control (T1),which was compared to Lolium perenne (T2),Purusfrumentum (T3) and Sorghum bicolor (T4).Samples of the surface runoff after rainfall from May to August in 2015 were collected and analysed for nitrogen (N) and phosphorus (P) allowing losses to be calculated.The results showed that all three forages significantly reduced N and P losses both in the runoff and the sediment.The most effective species was P.frumentum;N and P losses caused by natural rainfall occurred mainly in sediment which accounted for 76.34％-79.97％ and 81.69％-83.90 ％ of total N and total P losses,respectively.The fresh and dry biomass yields of L.perenne and P.frumentum were higher than corn,the mean advantage being 4.45 and 1.52 times,and 4.89 and 1.53 times that of corn,respectively.The nutrient sequestration effect of the four crop types were ranked T2,T3＞T4＞T1.The nutrient sequestration and feed economic benefits of P.frumentum indicate that it has the greatest potential as a substitute for corn in Three Gorges Reservoir catchments,followed by L.perenne.