紫色土区不同植物篱模式控制坡耕地氮素流失效应

为优选紫色土区控制农田氮磷等养分流失的复合农林模式,利用野外径流小区试验,结合室内分析与数理统计法研究了植物篱模式控制紫色土区坡耕地氮素流失效应。结果表明,植物篱模式减少了坡耕地总氮及各形态氮流失负荷,就总氮而言,20°坡耕地紫穗槐与香根草模式下年均总氮流失负荷分别比横坡农作模式降低92.4%、90.0%;13°坡耕地紫花苜蓿与蓑草模式的年均总氮流失负荷分别比横坡农作模式降低88.7%、83.9%。径流与泥沙流失量的减少与径流氮浓度的降低是植物篱控制坡耕地氮素流失的主要机制。紫穗槐、香根草、紫花苜蓿与蓑草植物篱模式可作为西南紫色丘陵区农业非点源氮素污染的源头控制技术,特别是20°以上坡耕地推广与实施灌木类植物篱模式,能长期有效地控制农田盈余氮素流失。

Effect of hedgerow patterns controlling nitrogen loss of slope farmland in purple soil area

Abstract: Agricultural non-point source nitrogen is one of the major sources for surface water eutrophication in the world. Hedgerows have been widely used as a measure of controlling soil, water and nutrient losses. However, there are few studies on nitrogen concentration loading and composition in runoff under long period hedgerow patterns in purple soil area of southwest China. Field experiments were carried out for three years to examine effects of 13-year hedgerow intercropping patterns for controlling nitrogen loss. There were six treatments: contour cropping (T1), Amorpha hedgerow plus contour cropping (T2), and Vetiver hedgerow plus contour cropping (T3) on 20° slope land, and contour cropping (T4), alfalfa hedgerow plus contour cropping (T5) and Eulaliopsis binata hedgerow plus contour cropping (T6) on 13° slope land. Results showed that in general, hedgerow patterns can reduce total nitrogen concentration and different forms of nitrogen in runoff. In terms of total N, compared with T1, average total nitrogen concentration in runoff decreased by 36.0%, 33.0% for T2 and T3 on the 20o slope farmland, respectively. Compared with T4, average total nitrogen concentration in runoff decreased by 5.9% for T5, and it had no significant decrease for T6 (P>0.05) on the 13o slope farmland. Enrichment rate of sediment nitrogen for hedgerow patterns was higher (P<0.05) than that of the contour cropping treatment. This indicated that hedgerow patterns can effectively control sediment nitrogen loss. Hedgerow patterns reduced total nitrogen and different form of nitrogen loss from slope farmland. In terms of total nitrogen, compared with T1, annual average total nitrogen loss under T2 and T3 was respectively reduced by 32.86 and 31.99 kg/hm2 accounting for 92.4% and 90.0% nitrogen loss reduction on the 20o slope farmland. Compared with T4, annual average total nitrogen loss under T5 and T6 was respectively reduced by 27.55 and 26.04 kg/hm2 accounting for 88.7% and 83.9% in nitrogen loss reduction on the 13o slope farmland. Therefore, Amorpha, Vetiver, alfalfa and Eulaliopsis binata hedgerow patterns can be used for controlling agricultural non-point pollution in purple soil area. Effects of different hedgerow patterns on controlling nitrogen loss were difference. On same slope, effects of Amorpha patterns controlling nitrogen loss was better than that of Vetiver, and effects of Alfalfa patterns controlling nitrogen loss was better than that of Eulaliopsis Binata. Effects of hedgerow patterns in controlling nitrogen loss increased with the increase in slope degree. Overall, shrub hedgerow patterns can be used to control nitrogen loss in runoff under 20o slope farmland. More research is still needed when slope is larger than 20o slope.