酸性紫色土上紫花苜蓿的结瘤性能与养分吸收

盆栽试验表明,在pH.5.45的酸性紫色土接种苜蓿根瘤菌,可显著提高紫花苜蓿地上部和地下部生物量。根瘤菌不同株系的结瘤性能和对宿主生长的影响存在显著差异,且不同紫花苜蓿品种的结瘤性能也存在显著差异。结瘤性能良好的菌株显著提高地上部氮、磷和钙的含量,而降低地上部钾含量和铝含量。紫花苜蓿地上部的氮、磷、钾和钙含量高于地下部,镁含量差异不大,而铝含量在接种后地下部含量高于地上部。相关分析表明,紫花苜蓿根瘤重和根瘤数与地上部生物量和地上部氮含量之间存在显著正相关关系;而地下部铝含量与地上部生物量、结瘤性能和植株氮含量呈显著负相关关系。说明酸性土壤良好的结瘤性能可提高生物固氮效率、促进紫花苜蓿生长,但根系铝的过量吸收影响紫花苜蓿的生长、结瘤与氮素吸收。

Nutrients absorption and nodulation ability of alfalfas in acid purple soil

Soil acidity is the main factor affecting plant production all over the world.Alfalfa cultivation in southern China also confronts this problem.In order to screen suitable alfalfa varieties and rhizobium for acid soil,5 months pod experiment was carried out to analyze the nodulation ability of different varieties and rhizobium in acid purple soil in three gorges reservoir.The purple soil was selected from hilly arable land in Beibei,Chongqing.Soil acidity was pH 5.45.Alfalfa was not cultivated in the land for the past ten years.Six Medicago sativa varieties used in trial were Zhongmu 1(A),Gannong 1(B),Gannong 3(C),Sandtti(D),Eureka(E) and Defi(F).The results showed that the root and shoot biomass of alfalfa were significantly increased by inoculating Sinorhizobium melilotii.Different rhizobia had significant difference in nodulation ability and their effects on plants,and different alfalfa varieties also had different nodulation abilities.The rhizobium with better nodulation ability increased the content of nitrogen,phosphorus and calcium in shoot,while decreased the content of potassium and aluminum in shoot.The content of nitrogen,phosphorus,potassium,calcium and magnesium in shoot were significantly higher than those in root,while the content of aluminum in root with inoculating rhizobia was significantly higher than that in shoot.Nodule weight and number were significantly correlated with shoot biomass and nitrogen content in shoot,while root aluminum content was negatively correlated with shoot biomass,root biomass,nodule weight,nodule number and nitrogen content.It indicated that good nodulation ability increased biological nitrogen fixation and growth of alfalfa.But over absorption of aluminum by root in acid purple soil constrained the nodulation and nutrient absorption of alfalfa,and thus influence the adaptation of alfalfa in acid soil.It was suggested in the paper that more alfalfa varieties and efficient rhizobia should be screened before the alfalfa were successfully planted in acid soil.