土壤盐胁迫对紫花苜蓿磷素利用的影响

[目的] 为了研究土壤磷肥和盐分及其交互作用对紫花苜蓿生长、磷营养和耐盐性的影响。[方法] 通过向[XC<0.TIF>;% 102% 102]土中添加不同浓度梯度的磷肥(0,40,80,160 mg/kg,以KH₂PO₄的形式添加)和氯化钠(0,0.4,0.8,1.6 g/kg)进行温室盆栽试验,种植紫花苜蓿"甘农七号"。[结果] 紫花苜蓿地上部生物量和地下部生物量均随着磷肥施加水平的提高而增加,但随着盐分添加水平的提高而减少;施磷时植物的磷吸收量增加,当磷水平为160 mg/kg时,根、茎、叶的磷含量均达到最大。添加盐分抑制对磷的吸收,当盐水平为1.6 g/kg时,根、茎、叶的磷含量与不加NaCl时相比显著减少;与不加磷肥时相比,酒石酸含量随着磷肥水平升高而减少,外源盐分添加显著增加紫花苜蓿根际酒石酸的含量;大部分处理的根际pH与非根际pH相比均降低,在盐胁迫的情况下土壤pH的降低提高土壤磷的有效性和植物对磷的吸收;高剂量(160 mg/kg)的磷肥添加使紫花苜蓿的磷吸收效率、磷利用效率均显著降低。[结论] 土壤磷肥与盐分之间存在显著的交互作用,盐分增加加剧植物磷缺乏,适当施用磷肥可提高紫花苜蓿的耐盐性,并提高其在盐渍土壤中的生产力。

Effects of Soil Salt Stress on Phosphorus Utilization of Alfalfa

[Objective] In order to explore the effects of soil phosphorus (P) fertilizer and salt and their interaction on the plant growth, P nutrition and salt tolerance of alfalfa (Medicago sativa). [Methods] Alfalfa "Gannon Ⅶ" was planted by adding phosphate fertilizer (0, 40, 80, 160 mg/kg, in the form of KH₂PO₄) and NaCl (0, 0.4, 0.8, 1.6 g/kg) with different concentration gradients to the loess soil. [Results] The aboveground and underground biomass of alfalfa increased with the increase of P application level, but decreased with the increase of NaCl addition level. When P was added, P uptake by plants increased. When P was added at 160 mg/kg, P concentrations in roots, stems, and leaves all reached the maximum. However, the addition of salinity inhibited the absorption of P. When NaCl was added at 1.6 g/kg, P concentrations in roots, stems, and leaves all significantly decreased, when compared with that without NaCl. The content of tartrate in rhizosphere of alfalfa decreased with the increase of P compared with that without P, and the addition of exogenous salt significantly increased the content of tartrate in rhizosphere. The rhizosphere soil pH of most treatments was lower than that of non-rhizosphere pH, the decrease of soil pH under salt stress might increase the availability of soil P and P uptake by plants. A high-dose (160 mg/kg) of P significantly reduced the P-uptake efficiency of P-utilization efficiency of alfalfa. [Conclusion] In summary, there was a significant interaction between soil P fertilization and salinity, and the increase in salinity exacerbated plant P deficiency. Appropriate application of P-fertilizers can improve the salt tolerance of alfalfa and enhance its productivity in saline soils.