Long-term Experiment On The Loess Plateau Soil Enzyme Activities

This paper reported the results of two long term experiments in dry land of loess plateau about soil enzyme activities including calatase, invertease, uresae, alkaline phosphatase, protase. Numbers of Bacteria, fungi, Actinomycetes, and microbial biomass carbon, nitrogen of same soil samples were analyzed. The effect of fertilization and rotation on soil biological properties were studied, especially soil enzyme activities and soil enzymatic factors expressed the influence of fertilization and rotation on soil biochemical quality.Soil nutrient content in the soil surface (0~20cm) were significantly affected by the long -term (15-16year) fertilization and rotation practices; organic fertilizer increased the soil organic carbon content and biological activities, which give a better environment to the growth of plants. Soil enzyme activities increased because not only the enzyme were put in soil along with organic fertilizer but also organic fertilizer give a better environment to soil microbe. Microbe can secrete a lot of enzyme, which is important to dry land agriculture of organic fertilizer efficiency.Long term fertilization and rotation increased the content of soil microbial biomass carbon and microbial biomass nitrogen. Increased Bc is as 62.3%~270% and increased BN is as 41.2%~353.1% as that of fallow land. Microbial biomass related to soil enzyme activities significantly, but microbe numbers of Bacteria, fungi, Actinomycetes do not related to soil enzyme activities, as the methods of microbe plate counts can not give that of actual field.Soil enzyme activities along with winter wheat bearing time had a little change, soil mobilized urease and alkaline phosphatase activities is 1 percent as total activity as its. With an increase in soil depth, there was a rapid decrease in invertase, urease, alkaline phosphatase and protase activities in the alfalfa continuous crop.Soil catalase activity was reduced by long-term fertilization remarkably, but fertilization increased invertase, urease, alkaline phosphatase and protase activities. According to correlation and path analysis, calatase activity was inversely related to soil organic carbon content and available P and alkaline phosphatase activity was inversely related to soil available P content, but soil organic carbon, total nitrogen, C/N were related to invertase, urease, alkaline phosphatase, protease activities; winter wheat yield was related to invertase, urease, alkaline phosphatase, protase activities and soil enzyme activities influenced the release of nutrients for plant and microbial growth, so it can indicated soil production.Different plants and rotation influenced soil enzyme activities because the amount and component of plant residue; effect degree of alfalfa, pea, sainfoin on soil enzyme activities was more than that of wheat, maize, potato.According to the results of Principal Components Analysis, soil enzymatic factors expressing soil fertility is consistent with that of soil chemical and microbe factors, which proved that soil enzyme activities is a index of dry land soil fertility and the information expressed by urease, alkaline phosphatase, protase activities was more than that of calatase and invertase activities.