Effects Of Fertilization And Rhizobium Inoculation On Growth And Soil Nutrient Changes Of Medicago Varia Martin.cv.Caoyuan No.3

During the cultivation of alfalfa,in addition to the constraints of climate,soil,and water,fertilization strategies(fertilization,frequency of fertilization,and inoculation of rhizobium)have become key factors affecting modern intensive and standardized production of alfalfa.In combination with local industrial practices,13 foreign and domestic alfalfa cultivars were selected for variety adaptability tests on long-time abandoned sandy land in 2015.The results showed that the Caoyuan No.3 was excellent in plant height,yield,and wintering rate.Therefore,further research on fertilization strategies of Caoyuan No.3 was carried out in 2016.Rhizobium inoculation(inoculation and non-inoculation of rhizobium)was set at the time of construction in 2016;based on the rhizobium inoculation,five fertilization rates(40,50,60,70,80 kg/mu)and 3 fertilizations frequencies(4,6,8 times)were performed in 2017.The after-effects of fertilization strategies continued to be observed in 2018.By analyzing the effects of different fertilization rates,fertilization frequency and rhizobium inoculation on alfalfa's above-ground biomass,growth rate,quality,nutrient distribution,soil stoichiometry,and subsequent yield,regreening,etc.,the response laws of alfalfa planted to fertilization in sandy land were summarized,which provide theoretical basis for alfalfa production and management mode in this area.The main results are as follows:1.Above-ground biomass,stem weight,growth rate and other indicators related to alfalfa yield were mainly affected by the linear and secondary effects of fertilization,and the interaction of rhizobium and fertilization frequency.The aboveground biomass was most affected by the amount of fertilization,and was less affected by the interaction between Rhizobium and the number of fertilization.Aboveground and underground biomass allocation is mainly negative affected by the interaction between rhizobium and fertilization frequency.The interaction of rhizobium × fertilization amount has a greater effect on the aboveground material allocation.2.The stem NDF,leaf NDF and leaf RFV were mostly affected by the interaction of Rhizobium and fertilization times.Leaf ADF is mainly affected by fertilization frequency,and stem ADF is mainly affected by rhizobium.Stem RFV and leaf protein content are mainly affected by the interaction of rhizobium and fertilization frequency.Stem protein content was mainly affected by secondary effects of fertilization frequency,interaction of rhizobium and fertilization amount,and interaction of fertilization amount and fertilization frequency.3.The soil inorganic carbon and NO3-N in alfalfa cultivated grassland were affected by the fertilization times,the secondary effects of rhizobium,the secondary effects of fertilization times,and the interaction of Rhizobium and fertilization times,among which the fertilization times were the most important.And soil NH4-N was most affected by the interaction between Rhizobium and fertilizer application times.There was typical correlativity among the Rhizobium,fertilization rate,fertilization frequency,soil total N and soil nutrients(inorganic carbon,NH4-N and NO3-N).The order of influence degree from large to small was as flows:rhizobium,fertilization rate and fertilization frequency and the ratio was 3.64:1.95:1.Notably,the influence coefficient of Rhizobium was 0.8581.4.The medium level of fertilization and rhizobium inoculation could significantly increase the aboveground biomass of alfalfa.In the second year,the combination with the largest aboveground biomass was rhizobium inoculation and fertilizer application rate of 60 kg/mu,and the combination with 6 times of fertilization was 17228.3 kg/hm2.Rhizobium could promote the growth rate of alfalfa before the last cutting,increase the root-shoot ratio of alfalfa,and underground biomass of alfalfa and decrease the content of ADF and NDF.After inoculation with rhizobium,the wintering rate of alfalfa increased significantly(10.8%),and at the same time,it helped the greening of alfalfa.The inoculation of rhizobium can reduce the amount of fertilizer used;the contribution of fertilization amount,rhizobium and fertilization frequency to soil characteristics is 60.10%,the contribution to alfalfa growth is 39.58%,and the contribution to alfalfa quality is 17.09%.5.Based on comprehensive consideration of Alfalfa yield,quality,regreening and soil nutrient utilization,the best fertilization strategy were rhizobium inoculation,fertilizing amount with 60 kg/mu and 6 times fertilized.