Effects of intercropping and AMF inoculation on phosphorus forms in red soils

Arbuscular mycorrhizal fungi (AMF) can help host plants in the uptake of nutrients, especially phosphorus (P). Intercropping also can promote use efficiency of P in soils and increase crop yield. In order to study the effects of different P additions and AMF treatments on the absorption and utilization of different forms of P of intercropping corps in red soils, a pot simulation experiment was conducted using the three-compartment method. Under maize-soybean intercropping system, the hyphal compartments were treated with different forms of P-no P (P0), inorganic P (potassium dihydrogen phosphate-IOP50) and organic P (soy lecithin-OP50). Different AMF treatments, including no AMF (NM), inoculation with Funneliformis mosseae (FM), were performed in the root chamber. Intercropped maize and soybean, mono-cropped maize and soybean were planted in the experiment. The results showed that compared with mono-cropping-FM and IOP50 treatment, P uptake in maize increased by 150.2% and P uptake in soybean increased by only 24.5% under intercropping-FM and IOP50 treatment. Except mono-cropped soybean and P0 treatment, FM inoculation significantly decreased available P content in hyphal compartment soils. In addition to soybean mono-cropping-FM treatment, IOP50 application yielded the highest soil available P content under mono-cropping, and the lowest under intercropping conditions. AMF inoculation increased the contents of Ca₂-P, Al-P, Org-P, O-Al-P and Ca₁₀-P to a certain extent, while intercropping significantly increased crop uptake of Ca₂-P and Fe-P in the soil. Under combined intercropping, FM and IOP50, the contents of Ca₂-P, Org-P and O-Al-P in the soil were higher (P < 0.05) compared with other treatments. Correlation analysis showed that Ca₂-P was significantly negatively correlated with P uptake in maize, while O-Al-P was significantly negatively correlated with P uptake in soybean. In conclusion, FM inoculation, P fertilizer application and intercropping all promoted P absorption and accumulation of host crops to a certain extent. Among these, FM, IOP50 and intercropping was the best combination for the promotion of intercropped maize growth, P uptake and increased Ca₂-P, Org-P and O-Al-P of red soil. If applied to Dianchi watershed, it is expected to reduce the loss of P.