| In order to study the contribution and mechanism of interactions of interspecific root?corresponding to the part of aboveground interactions?and nitrogen addition on the formation of nodule and nitrogen fixation and forage population yield in mixed planting of legume and gramineae artificial grassland,the mixed planting of alfalfa and smooth brome was taken as the research object in this study and the"root separated microzone experiment"was established by using the 3×2 split zone experiment design.To set up three root separated treatment:non separation?NB?,the roots are separated by nylon nets?MB?,and the roots are separated by PVC plates?SB?.The treatment which roots are separated by PVC plates is contrast.The plant growth status,grassland population yield and alfalfa nodules nitrogen fixation in artificial grassland were measured and analyzed at two nitrogen levels:0 and 150 N kg·hm-2(the actual addition amounts were urea 0 and 1.28 g·pot-1,writed for N0 and N150),for the sake of deepen the understanding of the mechanism of root interaction between legume and gramineous forages.It provides some helpful explanations for the improvement of forage yield and quality and the sustainable utilization of artificial grassland with mixed planting of legume and gramineae.The main research consequences are as follows:?1?Treatment separated by nylon nets significantly increased the aboveground biomass of alfalfa?P<0.05?,and the proportion of alfalfa in the total production of mixed pasture was increased.Treatment separated by nylon nets significantly reduced aboveground biomass compared to smooth brome of non separation smooth brome?P<0.05?,but this was not different from the effect of treatment separated by PVC plates on biomass of smooth brome.In addition,the root biomass,nodules and nitrogen fixation of alfalfa separated by nylon net were significantly higher than those treated by non separation or separated by PVC plates?P<0.05?.At the same time,the nitrogen content in part of aboveground of alfalfa and smooth brome and the nitrogen accumulation in mixed mixed planting grassland were significantly increased?P<0.05?.The plant growth,tiller number and the growth of aboveground and belowground biomass and root-shoot ratio of smooth brome were significantly increased by non-separation?P<0.05?,and therefore,to increase the proportion of smooth brome in the total production of mixed planting grassland.However,the plant growth and branching of alfalfa were significantly and negatively affected,and the growth of the aboveground part and root system of alfalfa was significantly inhibited?P<0.05?.?2?The total yield of mixed grassland,plant growth,tiller number and aboeground biomass,underground biomass of smooth brome were significantly increased,and the root-shoot ratio of smooth brome was significantly reduced with nitrogen addition?P<0.05?.The plant growth and underground biomass of alfalfa had no significant response to nitrogen addition,but The root-shoot ratio of alfalfa was significantly increased and the branch number,nodule number and nodule weight of alfalfa were reduced significantly?P<0.05?.?3?There was an interaction between root separation and nitrogen addition on alfalfa branch number,aboveground biomass,total yield of mixed planting grassland and aboveground nitrogen accumulation:The addition of nitrogen significantly reduced the number of branches of alfalfa on treatment of separated by nylon nets as well as increased the total yield of mixed planting grassland on non separation?P<0.05?.Treatment separated by nylon nets significantly increased the number of alfalfa branches and aboveground biomass under N0 treatment,along with the total production and nitrogen accumulation of mixed planting grassland?P<0.05?.In summary,among the three root separation treatments in this study,the semi-interspecific root interaction of nylon net separation could promote the proportion of alfalfa in total grassland production,and the efficiency of biological nitrogen fixation was improved and the nitrogen content and nitrogen accumulation in mixed planting grassland were increased.The addition of nitrogen could increase the total yield of mixed planting legume and gramineae grassland. |
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