低磷条件下玉米‖蚕豆间作作物根系间距对玉米磷吸收的影响

为探究不同根系间距下禾本科作物玉米(生长和磷吸收)受相邻作物玉米或蚕豆的影响，本研究以玉米为目标作物，通过圆柱形根箱培养试验，设置单株玉米、单作玉米、玉米‖蚕豆间作并改变相邻作物根系间距，探究低磷条件下，不同根系间距的相邻作物对目标玉米的生长、磷吸收和根际过程的影响。结果表明:1)与单株玉米相比，目标作物玉米与相邻作物玉米和蚕豆之间均以竞争为主，当作物根系间距较近时，单作玉米的生物量、磷含量分别下降21%、33%，间作玉米分别下降34%、31%；当作物根系间距较远时，单作玉米的生物量、磷含量分别下降10%、15%，间作玉米分别下降29%、29%。2)当根系间距较近时，蚕豆的根际pH低于玉米，且间作玉米和蚕豆之间的根际pH存在显著差异，而在根系间距较远的处理中两作物的根际pH无差异；相邻作物根系间距较远时，间作玉米的根际有机酸浓度显著高于单作玉米，间作玉米与单作玉米的根际有机酸浓度在根系间距较近时无差异。3)不同处理中单作和间作玉米的总根长、总根表面积无差异。综上所述，在低磷条件下，单作玉米的种内竞争强度随根系间距的增大而降低；而在不同根系间距下，间作玉米与蚕豆的种间竞争强度相似且无种间磷吸收促进作用。因此，种间根际互作形成的磷吸收竞争作用或促进作用依赖于适度的土壤磷供应。

Effects of root distances between intercropped maize and faba bean on the phosphorus uptake of maize under low phosphorus conditions

This study aimed to explore the effects of different root distances between maize and neighboring maize or faba bean on maize(growth and phosphorus(P)uptake). The target maize was planted in a cirlindrical rhizo-box in single or monocropped with maize or intercropped with faba bean with different root distances under low P conditions. The P content, biomass and rhizosphere process of plants in different treatments were determined. The results showed that: 1)Compared with the single maize, there was competition between the target maize and neighboring plants regardless of the neighbouring plant species was monocropped maize or intercropped faba bean. When the root distance between the monocropped maize was close, the biomass and P contents of monocropped maize decreased by 21% and 33%, respectively, while that of intercropped maize decreased by 34% and 31%; respectively. When the distance between neighboring plants was large, the biomass and P contents of monocropped maize decreased by 10% and 15%, respectively, while that of intercropped maize decreased by 29% and 29%, respectively. 2)When the root distance between maize and faba bean was close, rhizosphere pH of faba bean was significantly higher than maize, but there was no significant difference between plants in intercropped treatments with large distance. Moreover, when the root distance between maize and faba bean was large, the rhizosphere carboxylates concentration of intercropped maize was higher than monocropped maize, while there was no significant difference in the treatments with close root distance. 3)There were no significant differences in total root length and total root surface area of monocropped and intercropped maize under different treatments. In conclusion, under low P condition, the intraspecific competition intensity of monocropped maize decreased with the increase of root distance; but the intensity of interspecific competition between maize and faba bean was similar among different root distance treatments and there was no facilitative P uptake. The competitive and facilitative P uptake through interspecific rhizosphere interaction could depend on moderate soil P supply.