| As high value crops planting area gradually expanded in China in the past years, farmers found soil borne disease became more and more serious. This has prompted the development of Chinese fumigation agent industry and Chinese farmers began to slowly familiar with fumigant. Through lab incubation experiments, we would to make sure the effect of soil fumigation on N nitrification and mineralization, the goal was to provide theoretical basis for scientific fertilization and improve nitrogen use efficiency. Through this experiment we got the following conclusions:1)The results of lab incubation presented that soil microbial biomass carbon and nitrogen all decreased sharply, soil organic nitrogen increased markly in the soils fumigated by different fumigants (Pic,1,3-D, DMDS and MS). This may be caused by microbial cells released by dead bacteria body and converted into organic nitrogen in the soil. Seven days after fumigation, the content of soil soluble amino acids rose to the highest value, and the mount of soil soluble amino acids in all of the fumigated soil were more than the unfumigated control(5.74mg·kg-1). We found that Pic treatment group was the highest(12.87mg·kg-1), followed by MS(10.56mg· kg-1), DMDS(10.35mg·kg-1) and1,3-D (9.54mg·kg-1) treatments.2)Through4fumigants indoor experiment, we found the concentration of ammonium nitrogen was increased significantly within a short-term period after treated with Pic,1,3-D, DMDS and MS. The soil nitrification was inhibited at least4weeks after treated with Pic,1,3-D and about2week treated with DMDS and MS. Soil fumigation could obviously influence the activity of soil enzyme:Pic significantly increased the soil protease activity, contrary, significantly decreased the soil protease activity, and1,3-D has no obvious effect. Fumigation decreased glutaminase and asparaginase activity in a certain extent, even if lifting of fumigation, soil enzyme activity is still relatively low.3)Adding a certain amount of Dazomet has significant effect on soil nitrogen loss by runoff when fertilize the soil with urea. After the conventional application of urea, in addition to the existence of a large number of soil ammonium nitrogen and nitrate nitrogen in the soil, there was also lots of nitrate nitrogen, the percent of nitrite nitrogen to total inorganic nitrogen was about15.7%-18.2%. However, the soils fumigated by Dazomet only had a little nitrite nitrogen, and it can also make the content of nitrogen in the soil existed mainly in the form of ammonium nitrogen for a long-term. This effect could reducing pollution of groundwater after application of nitrogen fertilizer.4)The biological characteristics on soil nitrification process in different fumigated soils were evaluated through the kinetic model of nitrification in soil. The results indicated that the4fumigats treatments all depressed nitrification for a short time. Soil fumigation retard the rate of conversion of ammonium to nitrate nitrogen significantly. The parameter tmax indicated Dazomet fumigation had the strongest inhibition of nitrification on Shanxi soil(tmax=8.78), and the least inhibition on Beijing soil(tmax=4.87). |
