[Root morphological changes in maize and soybean intercropping system under different phosphorus levels]

A pot experiment was conducted to investigate the changes of root morphology and its relationship with P uptake under different P levels (0, 50 and 100 mg P₂O₅·kg^-1, represented by P₀, P₅₀ and P₁₀₀, respectively). The results showed that intercropping significantly changed root morphological parameters of both maize and soybean, and increased the root:shoot ratio in soybean under different P levels. Intercropping significantly increased root length, root surface area, root volume, and root dry weight of maize and soybean by 25.6%, 22.0%, 39.2%, 34.3% and 28.1%, 29.7%, 37.3%, 62.3%, respectively, but significantly decreased the average root diameter by 15.2% and 11.7% compared to corresponding monoculture. The phosphorus uptake equivalent ratio (LER_P) was >1, showing P uptake advantage of intercropping and that the LER_P were unaffected by P levels. The root morphological changes induced by intercropping were closely related to P uptake improvement. The increases of maize root surface area and soybean root length were the main mechanisms driving efficient P uptake in maize and soybean intercropping. Based on the regression equation, 10% increase of maize root surface area or soybean root length caused 5%-10% increase of phosphorus uptake. P uptake of intercropped maize was not declined under P₅₀ level compared to that of monoculture supplied with P₁₀₀ level. In conclusion, maize and soybean intercropping has the potential to maintain crop P uptake when reducing application of phosphate fertilizer.