Effects of Sheep Urine Nitrogen on Biomass and Nitrogen Utilization in Alfalfa and Tall Fescue Mixed Grassland
To investigate the utilization of nitrogen in sheep urine in alfalfa(Medicago sativa L.)and tall fescue(Festuca arundinacea Schreb.)mixed grassland,the experiment set up three kinds of grassland types:alfalfa mono-sowing,tall fescue mono-sowing and alfalfa+tall fescue mixed sowing,and two types of sheep urine:addition or not,and combined into a total of 6 treatments.The changes of above-ground biomass,nitrogen recovery rate,bio-logical nitrogen fixation rate and nitrogen transfer of sheep urine with stable isotope 15 N labeling were studied.The results showed that the above-ground biomass of mixed sowing was significantly higher than that of single sowing tall fescue,the above-ground biomass of mixed sowing and single sowing tall fescue was significantly increased after adding sheep urine,and the nitrogen accumulation per plantlet for alfalfa and tall fescue was increased by sheep u-rine.The biological nitrogen fixation efficiency of alfalfa decreased after the application of sheep urine.9.42％of nitrogen was transferred from alfalfa to tall fescue without sheep urine,but no nitrogen was transferred between two plants when sheep urine was applied.The recovery rate of sheep urine nitrogen in mixed sowing was signifi-cantly higher than that of alfalfa and tall fescue mono sowing,and the recovery rate of sheep urine nitrogen in mixed sowing was significantly higher than that of alfalfa.Mixed sowing grassland grazing utilization could be beneficial to the high efficiency production and environmental protection,is a sustainable grassland utilization mode.
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