Effect-of Different Rhizobium Dosages On Growth Of Alfalfa In Kubuqi Sandland

Poor soil fertility is one of the most critical influences on ecological restoration of vegetation on decertified land.Alfalfa(Medicago sativa L.)planting in Sandland of Northwest China will promote economic development as well as improve soil quality,making use of land effectively.However,the growth and quality of alfalfa are limited by the poor soil of Sandland.Rhizobium inoculation enhances nitrogen fixation,promoting alfalfa growth with less fertilizer,lower cost.It is more environmental friendly.Rhizobium incolation will be an effective way to increase alfalfa yield and quality.The main soil type of Kubuqi Sandland is aeolian sandy soil.Low organic matter content and poor fertility cause difficulty on restoration of vegetation.To explore alfalfa with high yield,nutrition quality and nitrogen fixation in Kubuqi Sandland,the effect of rhizobium dosage on the growth and nodule characteristics of alfalfa was investigated there in 2016.The seeds of Alfalfa 'BR4010 ',' Junengll 'and 'BL103' were mixed with Rhizobium Dormal at the ratio of 0g·kg-1,10g·kg-1 and 20g·kg-1 and sown.Each treatment had three duplicates.The index of growth,nodules,yield and nutrient was measured periodically.The results showed that:(1)Rhizobium significantly increased growth rate and plant height.The difference of plant height with three rhizobium treatments was greatest in early bloom stage.Treatment 20g·kg-1 resulted in the greatest value and it made the plant 15.4cm taller than the plant without rhizobium.(2)Rhizobium promoted alfalfa nodulation and caused a significant increase in nodule number at the beginning of growth.The nodule number with rhizobium was 20 times more than nodule number without rhizobium.The nodule number without rhizobium increased slightly and never exceeded nodule number with rhizobium.The results of treatment 20g·kg-1 and 10g·kg-1 had not significant difference.Effective number of nodules and lateral root nodule number accounted for a large proportion of total root nodule number and showed a similar variation trend.(3)Hay yield increased as rhizobium dosage increased.Hay yield with rhizobium was 1505.3 kg·hm-2 higher than without rhizobium.Alfalfa 'BR4010' under treatment 20g·kg-1 had the maximum yield.Rhizobium decreased stem-leaf ratio.Treatment 10g·kg-1 caused the minimum stem-leaf ratio and the stem-leaf ratio without rhizobium was 26.9%higher than the minimum.(4)Rhizobium promoted nutrition quality.Treatment 10g·kg-1 often caused the best nutrition quality.CP content increased 23.6%,ADF and NDF content decreased 12.5%and 10.9%;and RFV and TDN with rhizobium increased 17.2%and 5.4%respectively.Nutrition content was significantly associated with stem-leaf ratio.All of the three cultivars were suitable to grow in Kubuqi Sandland,but the influence of rhizobium appeared somewhat different.In order to gain the maximum yield,alfalfa with treatment 20g·kg-1 was the best choice.But the best nutrition quality often caused by treatment 10g·kg-1.In practical production,factors including the cost also need to be taken into account to determine the best alfalfa cultivar and rhizobium dosage.