4种熏蒸剂处理对土壤可溶性有机氮和微生物量碳氮的影响

采用室内恒温通气培养法,以北京大棚蔬菜地土壤为研究对象,以未使用熏蒸剂土壤为对照,研究4种熏蒸剂氯化苦(Pic)、1,3-二氯丙烯(1,3-D)、二甲基二硫(DMDS)和威百亩(MS)]对土壤可溶性氮素和微生物量碳、氮的影响。结果表明,4种熏蒸剂处理均能增加土壤中可溶性有机氮的含量,熏蒸处理后敞气0 d时,Pic、MS、DMDS和1,3-D处理的土壤可溶性有机氮累积量分别为47.55 mg·kg-1、42.15 mg·kg-1、40.34 mg·kg-1和32.02 mg·kg-1,较对照(29.97 mg·kg-1)分别增加58.67%、40.65%、34.61%和6.87%。敞气后14~84 d,Pic、DMDS和MS处理DON含量仍持续上升,1,3-D和对照变化不大,各处理之间DON含量差异显著。4种熏蒸剂处理后短时间内,土壤中可溶性氨基酸(DAA)与对照相比大幅上升,在熏蒸后7 d达到最大值,其中Pic处理的上升幅度最大,为12.87 mg·kg-1,对照DAA含量最低,为5.74 mg·kg-1。4种熏蒸剂处理之后,土壤中微生物量碳和氮均呈现急剧下降的趋势,其中Pic处理对微生物的杀灭作用最强,敞气后0 d,Pic处理的微生物量碳和微生物量氮含量分别比对照下降69.39%和70.95%,MS和DMDS次之,1,3-D的杀灭作用最弱。

Effects of four fumigants on dissolved soil nitrogen transformation and microbial biomass

In a laboratory incubation under constant temperature and aerated conditions, the effects of 4 fumigants - chloropicrin (Pic), 1,3-dichloropropene (1,3-D), methyl disulfide (DMDS) and metham-sodium (MS) - on soil dissolved organic nitrogen (DON) transformation and microbial biomass under vegetable greenhouse conditions in Beijing area were investigated. The results revealed that DON concentration increased significantly after fumigant treatment. In 0 day after fumigation (DAF), cumulative DON under Pic, MS, DMDS and 1,3-D treatments were 47.55 mg·kg^-1, 42.15 mg·kg ^-1, 40.34 mg·kg^-1 and 32.02 mg·kg^-1, respectively. This represented a corresponding increase of 58.67%, 40.65%, 34.61% and 6.87% compared with 29.97 mg·kg^-1 of untreated soils. In the 14 84 DAF, the content of DON in Pic, DMDS and MS groups increased. A significant difference was noted in DON content in different groups. Fumigation also strongly increased the proportion of dissolved amino acid (DAA) in DON, which was important in the transformation process of soil N. DAA content increased greatly after fumigation, compared with CK, and peaked in 7 DAF. The highest DAA content (12.87 mg·kg^-1) was found under Pic treatment, while the lowest (5.74 mg·kg^-1) under CK. After fumigation, the content of soil microorganisms decreased sharply. Pic exhibited the strongest killing effect. Soil microbial biomass carbon and soil microbial biomass nitrogen contents decreased by 69.39% and 70.95%, respectively, under Pic treatment, followed by DMDS and MS treatments. Then 1,3-D had the least effect on microorganisms. While nitrification was inhibited for at least 2 weeks after treatment with Pic, 1,3-D and MS; it was inhibited for at least 1 week after DMDC treatment. Nitrification and mineralization gradually recovered under long-term incubation.