Soil Carbon And Nitrogen Fractions And Soil Microorganism Activities In Lucerne-crop Rotation Systems On The Loess Plateau

By setting long-term positioning experiments in Town of Lee's,Dingxi City,Gansu Province,research on the loess plateau in western rainfed agriculture perennial alfalfa ploughing up after rotation crops on soil carbon and nitrogen form and its related enzyme activity,the influence of which includes clover and alfalfa hay crop rotation system(L-L),alfalfa-leisure(L-F),alfalfa-wheat(L-W),alfalfa-corn(L-C),alfalfa-potato(L-P)and alfalfa-millet(L-M).The paper through the analysis to investigate the different crop rotation system and its related enzyme activity of soil carbon and nitrogen form different characteristics,hope the paper reveals the evolution law of soil fertility,crop rotation system in the region of alfalfa management measures,tillage system stability,sustainable utilization and upland crops production to provide scientific basis for the effective theory.Research conclusions are as follows:(1)The alfalfa-crop rotation model is not conducive to the accumulation of total organic carbon in the soil,while the alfalfa can maintain a higher level of organic carbon after the fall of the alfalfa.Compared with the alfalfa continuous cropping,the soil organic carbon of the alfalfa grain cropping pattern The total nitrogen content of alfalfa was the highest,and the total nitrogen content of alfalfa was the lowest,which indicated that long-term planting alfalfa could effectively maintain and balance soil nitrogen,so as to maintain and improve soil surface fertility.(2)Under the rotation mode,the soil total nitrogen content of the soil was only significantly higher than that of the alfalfa-crop rotation,while the soil non-acidolysis organic nitrogen was not significantly different between treatments The ratio of total nitrogen to non-acid-hydrolyzable nitrogen> acid hydrolysis unknown nitrogen> amino acid nitrogen> ammonia nitrogen> amino sugar nitrogen.(3)Soil acidolytic ammonia nitrogen and acid-hydrolyzed amino acid nitrogen in the soil were different from 0-10 cm and 0-30 cm in the soil,respectively.The results showed that alfalfa continuous cropping was higher than that of alfalfa-Crop rotation and leisure,soil acid hydrolysis of unknown nitrogen in the surface layer 0-10 cm showed alfalfa continuous cropping and leisure was significantly higher than alfalfa-crop rotation,soil acid hydrolysis of amino sugar nitrogen in the treatment there was no significant difference.(4)Compared with alfalfa continuous cropping,alfalfa grain cropping pattern reduced soilcatalase and protease activity,and increased soil nitrate reductase activity.Soil catalase activity and protease activity decreased by 5.20% 12.30% and 15.03% ~ 43.43% respectively,and the activity of nitrate reductase increased by 1.26% ~ 28.79%.There was no significant difference in soil urease activity between alfalfa continuous cropping and alfalfa-grain cropping pattern,but higher than that of alfalfa-leisure treatment.The correlation analysis showed that soil urease activity was positively correlated with soil organic carbon and total nitrogen,and could be used as an index to measure soil fertility.(5)Different rotation mode 0-24 h AWCD are lower,the carbon source is basically not used.With the prolongation of culture time,the utilization ability of microorganisms to carbon source was enhanced,and the surface layer 0-10 cm showed that the soil microbial metabolic ability was strong in alfalfa-leisure mode,and the soil microbial metabolic capacity was stronger in 10-30 cm soil layer.