Effects Of Tetracycline Contained Organic Fertilizers On Soil Miceobe And Pakchoi Growth

At present, antibiotics represented by tetracycline (TC) were employed as growthpromoters in livestock raising, and most of the TC uptake was eliminated in the forms oforiginal antibiotics and antibiotic metabolites by defecating and urinating, so that the composthas high contents of TC. TC is a broad-spectrum antibiotic, and the effects of organicfertilizer containing TC on ecological security after plowing soil is an important problem ofits applications in agriculture. In this paper, through the soil culture experiment and thepakchoi pot test, we studied the effects of TC contained organic fertilizers on soil microbecommunities, soil enzyme activities, soil nutrient and pakchoi growth. The results obtainedmainly were:1. Effects of TC contained organic fertilizers on soil microbe communities(1) The organic fertilizer made from pig waste with the average TC content (commonly,pig wastes have a TC content of5.22mg/kg) and wheat straw by composting could providesoil microbes with abundant nutrients, thereby increasing their vigor and then modifying theircommunity diversities. How much the TC contained organic fertilizer affected soil microbeswas related to its TC contents. By the hormesis of TC, the organic fertilizer with high TCcontents (2.5-5.0mg/kg) could significantly increase the capabilities of soil microbes to usethe four carbon sources: carbohydrates, amino acids, carboxylic acids and polymers (P<0.05).(2) The TC contained organic fertilizer could modify growing environments for soilmicrobes, and microbe populations capable of efficiently utilizing organic fertilizer nutrientsand being activated by TC could grow more vigorously, with consequence that differentexploiting capacities on carbon sources ensued.2. Effects of TC contained organic fertilizers on soil enzyme activities and soil nutrient(1) The organic fertilizer containing85mg/kg TC inhibited the soil invertase activitysignificantly (P<0.05). In the germination stage, the organic fertilizer containing TC couldimprove the soil alkaline phosphatase activity. Along with the extension of time, thepromotion of TC was not significant. The organic fertilizer containing0~85mg/kg TC couldimprove the urease activity, restrain the hydrogen peroxide enzyme activity, but the effect ofTC in it was not obvious. (2) The organic fertilizer containing0~85mg/kg of TC could significantly improve thesoil available nutrients (P <0.05). In the seventh day after fertilization, TC in the organicfertilizer reduced the soil available phosphorus. But along with the extension of time,difference was smaller. In seedling stage and rosette period, soil available potassium of5,45and85mg/kg treatment was significantly higher than0mg/kg treatment. In addition, TC inthe organic fertilizer improved soil ammonium nitrogen content.3. Effects of TC contained organic fertilizers on pakchoi growthThe effects of the organic fertilizer containing TC on the pakchoi growth relied on theconcentration of the TC in it. The higher the content of TC in0，5，45and85mg/kg treatmentswas, the lower the content of chlorophyll in pakchoi was; there was a striking negativecorrelation between the root vigor and the concentration of TC in fertilizers. If theconcentration of the TC was below45mg/kg, the fertilizer could promote the pakchoi growthand was suitable for the planting of pakchoi. When the concentration of the TC was as highas85mg/kg, it could restrain the root growth of the pakchoi, reduce the plant height andweight.