Effects of AMF and intercropping on crop yield and soil nitrogen and phosphorus loss by runoff on slope farmland

Abstract: Loss of nitrogen and phosphorus in sloping farmland is the main factor leading to river and lake pollution. Arbuscular mycorrhizal fungi(AMF) can activate soil nitrogen and phosphorus, and promote plant nutrient absorption. Intercropping can promote nutrient complementarity between plants. In order to quantitative study the synergistic reduction contribution of Arbuscular mycorrhizal fungi and maize-soybean intercropping system to runoff nitrogen (N) and phosphorus(P) loss, a field experiment was conducted in this study. The study area lies in Ecological Science and Technology Demonstration Park of Soil and Water Conservation (24°33′-24°37′N, 102°33′-102°38′E), which is located in Dachunhe small watershed, in Jinning County, Yunnan Province, China. The soil is red soil. The experiment was laid out using 20 m × 1.6 m plots with slope of 15°. The intercropping maize-soybean, mono-maize and mono-soybean treatment were designed, and the mycorrhizal inhibition treatment (application of benomyl which can specifically inhibit the growth of mycorrhizal fungi)was as a controlled trial. The results showed that: compared with mono maize - mycorrhizal inhibition treatment, maize intercropping- none mycorrhizal inhibition treatment significantly increased maize biomass. Compared with mono - mycorrhizal inhibition treatment, maize and soybean intercropping- none mycorrhizal inhibition treatment significantly increased the leave and grain P uptake, and significantly increased the leave and root N uptake by the plants. Compared with mono maize-mycorrhizal inhibition treatment, the reduction of total P and total N respectively was 0.25 and 0.11 g/kg in soils with intercropping maize-non mycorrhizal inhibition treatment, the reduction of total P and TN in runoff was 0.13 and 12.94 mg/L respectively. Compared with mono soybean- mycorrhizal inhibition treatment, the reduction of TP and TN respectively was 0.07 and 0.11 g/kg in soils with intercropping soybean- non mycorrhizal inhibition treatment, the reduction of total P and total N was 0.27 and 24.80 mg/L in runoff respectively. Compared with mono - mycorrhizal inhibition treatment, the TP and TN loss were decreased by 0.51 and 19.93 kg/hm2 in maize-soybean intercropping-non mycorrhizal inhibition treatment, respectively. The correlation analysis showed that the concentration of particulate P in runoff was negatively correlated with the P uptake by various parts of the plant, and negatively correlated with the TP and available P content in soil. The N concentration of different forms in runoff was negatively correlated respectively with the N uptake by various parts of plants,hyphal density and glomalin content. It can be seen that the AMF and maize-soybean intercropping mode can directly reduce the N and P loss in runoff by promoting the absorption of N and P nutrients by the plants. Therefore, AMF and maize-soybean intercropping mode can intercept the total loss of nitrogen and phosphorus in the runoff. The research can provide references for controlling agricultural non-point source pollution.