Interactive Effects Of Alfalfa Cultivars Rhizobia Inoculation And Soil Nutrient On The Rrowth And Nodulation Of Alfalfa

During the cultivation of alfalfa, the technique of rhizobia inoculation can significantly increase the fresh yield, and improve soil nitrogen content. However, different rhizobia may be suitable to parasitize different cultivars of alfalfa, which can make the yield of alfalfa contrasting. Therefore, it’s of great importance to screen the suitable combinations of alfalfa and rhizobia which owe the high ability to reproduce root nodule and fix nitrogen. To study the growth and root nodule of different Medicago materials under different soil conditions, we planted six Medicago materials(Medicago falcate L. cv. Hulunbeier, M. ruthenica (L.) Sojak. cv. Zhilixing, M. varia Martin, cv. Caoyuan No.3, M. sativa L., M. lupulina L and M. truncatula cv. Jamelong) in two types of soils with contrasting available N and P content in greenhouse experiment, and measured the plant height, above-ground biomass, branch number, root nodule number and weight of alfalfa. Meanwhile, to compare the growth of alfalfa under infection of different rhizobium, we selected three varieties of Medicago (M. sativa L. cv. Aohan, M. varia Martin, cv. Caoyuan No.3, M. sativa L) which were then inoculated different rhizobia (CK, Dormal and native variety) in field experiment. Soil nutrient content (total nitrogen, total carbon, available nitrogen, available phosphorous and total sulfur content) were also determined to analysis the changes in soil nutrient under different treatments. The main results were as follows:1. The results showed that except the M. ruthenica, the biomass of all other five materials was higher under the soil condition with higher available N and P content. In addition, except the M. varia Martin, cv. Caoyuan No.3, the root nodule number and weight of other five materials were larger under more fertile soil condition. Furthermore, at soil condition with higher N and P availability, the biomass of plants had significantly positive correlation with number and weight of root nodule for all Medicago materials at branching stage.2. There was no significant difference in above-ground biomass among the three varieties of Medicago at early stages. However, the above-ground biomass of two cultivated varieties of Medicago (M. varia Martin, cv. Caoyuan No.3 and M. sativa L) were significantly higher than the native variety (M. sativa L. cv. Aohan) at late stage. In addition, after induced by native rhizobium, the three varieties grew better than that induced by Dormal. Furthermore, we found that the Medicago increased soil available N and decreased soil total K and S content.