滇池流域坡耕地土壤氮磷流失效应

为了揭示间作对坡耕地上不同类型土壤径流和侧渗氮(N)、磷(P)浓度的削减及作用机制,通过径流和淋溶模拟试验,设置不同类型土壤(红壤和紫色土)、坡度(8°和15°)和玉米(Zea mays L.)/大豆(Glycine max L.)间作及各自单作对照,比较分析了各因素影响下径流和侧渗N、P浓度的变化情况。结果表明:(1)径流总氮(TN)、总磷(TP)在红壤不同坡度条件下,与单作大豆处理相比较,间作处理对径流TN浓度有不同程度的削减作用,分别降低27.5%和30.8%,且间作处理下TN浓度在坡度为8°时最低为0.75mg/L;在紫色土8°条件下,与单作大豆、单作玉米相比,间作处理对径流TN浓度的削减效应更为明显,降幅分别为97.8%和89.8%,与单作玉米处理相比较,间作处理对径流TP浓度均有不同程度的削减作用;从8°至15°处理,径流TP浓度相应有所增加。(2)侧渗TN、TP在红壤8°和15°条件下,与单作玉米相比,间作处理对侧渗TN浓度也有较大的削减作用,分别降低87.9%和86.8%,且在8°时侧渗TN浓度最低为2.91mg/L;在紫色土8°和15°条件下,与单作玉米处理相比,间作处理对侧渗TN浓度有约50%和80%的降幅,与单作玉米处理相比较,间作处理对侧渗TP浓度亦有不同程度的削减作用;其中红壤8°条件间作处理下侧渗TP浓度最高为0.25mg/L,15°条件间作处理下TP浓度最低为0.07mg/L。不同坡度条件下,土壤中N、P的输出量不同,且随着坡度增大,径流或侧渗中N、P总体的流失量也呈一定的增加趋势。玉米/大豆间作体系对径流和侧渗中的N、P有一定的削减作用;对于红壤和紫色土,由于其自身理化性质的不同,对坡耕地土壤中N、P流失的削减效应也不尽相同。因此,控制坡耕地氮、磷流失应综合考虑各种因素,对于保护滇池流域水环境具有重要意义。

Soil N and P Loss in Slope Farmland of Dianchi Watershed

The present study aimed to reveal the effects of intercropping on soil runoff and lateral seepage nitrogen (N), phosphorus (P) loss in different types of slope farmland. A runoff and leaching simulating experiment was conducted, different types of soil (red soil and purple soil) and slopes (8° and 15°) and planting patterns maize (Zea mays L.)/soybeans (Glycine max L.) intercropping and mono-maize and mono-soybeans) were designed, the changes of N and P concentrations in runoff and lateral seepage under the influence of various factors were analyzed. The results showed that:(1) In the case of the total nitrogen (TN) and total phosphorus (TP) of runoff:under different slope in red soil, compared with mono-soybean, intercropping has different reduction effect on TN, the reductions were 27.5% and 30.8%, respectively, and the TN under intercropping was the lowest, which was 0.75 mg/L at the slope of 8°. Under the slope of 8° in purple soil, compared with mono-soybeans and mono-maize, the reduction of intercropping on TN of runoff was more obvious, and the reductions were 97.8% and 89.8%, respectively. Compared with mono treatment, intercropping had the different reduction on TP of runoff. However, the TP of runoff increased from the slope of 8° to 15°. (2) For the lateral seepage TN, TP, under the slope of 8° and 15° in the red soil, compared with mono-maize, intercropping had a greater reduction of the lateral seepage TN, which had 87.9% and 86.8% reduction, respectively, as well as the lowest concentration of TN was 2.91 mg/L at 8°; under the slope of 8° and 15° in purple soil, the reduction of intercropping on TN of lateral seepage were 50% and 80%, respectively. Compared with mono-maize, intercropping also had the different reduction on TP of lateral seepage; and the TP under the slope of 8° in red soil of intercropping was the highest with 0.25 mg/L, and the TP under the slope of 15° red soil of intercropping was the lowest with 0.07 mg/L. The output of N and P in soil was different under different slope treatments and the total loss of N and P in runoff or lateral seepage would increase with the slope increasing. In conclusion, the maize/soybean intercropping system had a certain effect on the reduction of N and P concentration in the runoff and lateral seepage. For red soil and purple soil, the reduction of the loss of N and P in the soil of slope farmland might be different because of their physicochemical properties. Therefore, controlling the loss of N and P in slope farmland should consider all kinds of factors, which is of great significance to protect the water environment of Dianchi Watershed.