不同磷水平下玉米-大豆间作系统根系形态变化

本研究通过盆栽试验,探讨不同磷水平(0、50、100 mg P₂O₅·kg^-1,分别用P₀、P₅₀、P₁₀₀表示)下玉米与大豆间作系统根系形态的变化及其与磷吸收的关系,以明确玉米-大豆间作系统促进磷吸收的作用机制。结果表明: 不同磷水平下,间作显著改变了玉米和大豆的根系形态参数,提高了大豆根冠比。与单作模式相比,间作使玉米和大豆的根长、根表面积、根体积、根系干重分别显著增加25.6%、22.0%、39.2%、34.3%和28.1%、29.7%、37.3%、62.3%,而平均根直径分别显著降低15.2%和11.7%。不同磷水平下,磷素吸收当量比(LER_P)>1,玉米-大豆间作具有明显的磷吸收优势,且LER_P不受磷水平调控。间作诱导根系形态改变与磷吸收增加密切相关,其中玉米根系表面积增大、大豆根系长度增加是驱动玉米-大豆间作系统磷高效吸收的主要机制。根据回归方程,玉米根表面积和大豆根系长度增大10%,磷吸收量提高5%～10%。因此,与中等施磷水平(P₁₀₀)下的单作相比,玉米-大豆间作条件下磷肥减施1/2(P₅₀)并未降低玉米的磷吸收量。综上,玉米-大豆间作体系在减施磷肥条件下具有维持作物磷吸收的潜力。

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.