不同农艺措施对巢湖沿岸坡耕地水土及径流氮输出的控制效果

Effects of Different Agronomic Measures on Runoff,Sediment and Nitrogen Losses from Sloping Cropland Around Chaohu Lake

基于巢湖沿岸坡耕地水土和养分流失监测的定位试验,于2014—2015年连续2a进行观测,研究小麦—芝麻模式下,植物篱(黄花菜)(PH)、植物篱+秸秆覆盖(PHS)和等高垄作(CR)3种农艺措施对水土和径流氮输出的控制效果。结果表明,植物篱、植物篱+秸秆覆盖和等高垄作能有效减少地表径流量和土壤流失量,3种农艺措施的降低效果依次为PHS>PH>CR。与CK(当地常规耕作)相比,PH、PHS和CR处理平均分别减少24.5%,36.5%和19.7%的径流流失和31.0%,45.6%和25.4%的土壤流失,表现出显著的水土保持作用,且减沙效果大于减流效果。3种农艺措施显著降低了径流液颗粒态氮(PN)的浓度,提高了溶解态总氮(DTN)、硝态氮(NO^-_3—N)和溶解态有机氮(DON)的浓度,但对总氮(TN)和铵态氮(NH^+_4—N)浓度无显著影响。CK处理径流液中PN和DTN所占TN的比例基本相当,而在其3种农艺措施下,DTN是N随着径流迁移的主要形态。在DTN中,NO^-_3—N占较大比例,DON次之,NH^+_4—N所占比例最小。CK处理N随地表径流平均年度累积流失量为9.35kg/hm^2,占当年施N量的2.83%。与CK相比,PH、PHS和CR处理的N素年度累积流失量平均分别降低了28.3%,40.7%和21.2%,其对N素输出的控制效应主要是通过减流减沙来实现的。该研究可为巢湖流域坡耕地水土流失和面源污染防治提供科学依据。

In order to test the efficiency of 3 agronomic measures on reducing runoff, sediment and nutrient losses, a 2--year field runoff plot experiment was carried out in a sloping cropland of sesame--winter wheat rotation system around Chaohu Lake. 4 treatments were applied., conventional tillage （CK）, plant hedgerow （PH）, plant hedgerow with straw mulching （PHS） and contour ridge tillage （CR）. The results in 2014-2015 showed that plant hedgerow, plant hedgerow with straw mulching and contour ridge tillage could significantly limit soil and water losses and the effects listed in the order of PHS〉PH〉CT. Compared with CK, PH, PHS and CR decreased runoff amount by 24.5%, 36.5% and 19.7%, respectively, and decreased sediment loss by 31.0%, 45.6%and 25.4%, respectively, implying the significant effects of the 3 agronomic measures on soil and water conservation, especially for sediment reduction. The 3 agronomic measures significantly reducedthe PN concentration in runoff, while increased the concentrations of DTN, NO3^- -N, and DON, and had no obvious influence on the TN and NH4^＋ -N concentrations. The proportions of DTN and PN to TN were almost the same in CK treatment, while DTN was the predominant form of N transported via runoff in the treatments of PH, PHS and CR. Nitrate nitrogen （NO3^- -N） was the major form of DTN in surface runoff, followed by dissolved organic nitrogen （DON）, and the proportion of ammonium （NH4^＋- N） was very low. The annual nitrogen loss in runoff from sloping cropland in CK treatment was 9.35 kg/hm^2 , which accounted for 2.83% of the nitrogen fertilizer application amount. Compared to the CK treatment, PH, PHS and CR treatments decreased annual nitrogen loss by 28.3%, 40.7% and 21.2%, respectively. Nitrogen loss was mainly decreased through the runoff and sediment reduction. This study could provide scientific basis for soil and water conservation, and regulation of non-point source pollution of sloping cropland in the Chaohu Lake region.