三种硝化抑制剂抑制土壤硝化作用比较及用量研究

Inhibition of DCD, DMPP and Nitrapyrin on soil nitrification and their appropriate use dosage

【目的】硝化抑制剂是调控土壤氮素转化与硝化作用微生物群落结构的有效途径。本文通过室内模拟试验对3种硝化抑制剂在不同剂量下的硝化抑制效果进行研究,旨在筛选出效果最佳的剂型与剂量,为石灰性土壤硝化抑制剂的合理应用提供依据。【方法】培养试验在生长箱内进行,25℃黑暗条件培养;盆栽试验在温室内进行。供试硝化抑制剂为双氰胺(DCD)、3,4-二甲基吡唑磷酸盐(DMPP)和2-氯-6-三氯甲基吡啶(Nitrapyrin),DCD和DMPP用量均设定为纯氮(N)量的0(CK)、1.0%、2.0%、3.0%、3.5%、4.0%、4.5%、5.0%、6.0%和7.0%;Nitrapyrin用量分别为纯氮量的0、0.1%、0.125%、0.2%、0.25%、0.3%、0.35%、0.4%、0.45%和0.5%,三种硝化抑制剂均设10个水平,每个水平3次重复。盆栽试验氮加入量为每公斤风干土0.50g,三种硝化抑制剂用量分别为纯氮用量的5%、1%、0.648%。调查比较了三者的硝化抑制效果及对土壤氮素转化的影响及其对小青菜鲜重的生物学效应;采用变性梯度凝胶电泳(DGGE)法分析了不同硝化抑制剂对土壤AOA、AOB群落结构的影响。【结果】DCD、DMPP、Nitrapyrin均可显著抑制土壤硝化作用(P<0.05),各硝化抑制剂处理土壤的NH_4^+-N含量分别较对照提高了46.2~256.1 mg/kg、291.8~376.7 mg/kg、3.68~372.9mg/kg。DCD与DMPP处理的硝化抑制率分别为49.3%~79.4%和96.4%~99.4%,DCD表现出明显的剂量效应,但DMPP在1%~7%浓度范围内的剂量效应不明显。Nitrapyrin在0.1%~0.2%浓度范围内有明显的剂量效应。0.25%~0.5%Nitrapyrin的硝化抑制率为98.9%~99.9%,其硝化抑制效果与DMPP处理相同。DCD、DMPP、Nitrapyrin处理的小青菜地上部分鲜重分别比氮肥处理(ASN)提高了12.7%、11.1%、17.6%。施用硝化抑制剂可改变土壤AOA和AOB群落结构,且对AOA群落结构的影响大于AOB,不同硝化抑制剂之间对AOA和AOB群落结构的影响无差异。【结论】3种硝化抑制剂的硝化抑制效果表现为Nitrapyrin≥DMPP>DCD,均对AOA与AOB群落结构产生明显影响。各硝化抑制剂处理均可提高小青菜地上部鲜重、叶片Vc含量及可显著提高小青菜叶片氨基酸含量(P<0.05)。综合比较,Nitrapyrin硝化抑制效果好于DMPP,DCD效果最差,推荐用量为基于纯氮0.25%的Nitrapyrin添加量。

【Objectives】Nitrification inhibitors are effective in regulating the transformation of soil nitrogen and the community structure of microbes which involve in the N nitrification process. Incubation and pot experiments were conducted to compare nitrification effects of 3 common used nitrification inhibitors, and to study the dosage for practical use in calcareous soil.【Methods】The incubation experiment was carried out in a plant growth chamber at 25℃ in dark condition, and the pot experiment was conducted in greenhouse. The tested three inhibitors were dicyandiamide（DCD）, 3,4-dimethylpyrazole phosphate（DMPP） and chloro-6-trichloromethyl-pyridine（nitrapyrin）. The dosage of DCD and DMPP designed as 0（CK）, 1.0%, 2.0%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0% and 7.0% of the N addition, those of nitrapyrin were 0, 0.1%, 0.125%, 0.2%,0.25%, 0.3%, 0.35%, 0.4%, 0.45% and 0.5%. N 0.50 g per kg of dry soil was added in pot experiment, and the dosages of three inhibitors were all 5%, 1%, 0.648% of the N addition. The nitrate inhibition rate and the biomass of pakchoi were investigated; the soil microbial community structures of AOA and AOB were analyzed using the method of denaturing gradient gel electrophoresis（DGGE）.【Results】Soil nitrification was significantly inhibited by DCD, DMPP and nitrapyrin（P 0.05）. Compares with the CK, soil NH_4＋-N concentrations were increased by 46.2–256.1 mg/kg with DCD, by 291.8–376.7 mg/kg with DMPP and by 3.68–372.9 mg/kg with nitrapyrin, respectively. The nitrification inhibition rates were 49.3%–79.4% with DCD and 96.4%–99.4% with DMPP. The DCD addition exhibited an obvious dose effect, namely, the nitrification inhibition rates were increased significantly with DCD dose increasing, the DMPP did not in the addition range of 1.0%–7.0%,Although nitrapyrin only showed dose response in low concentrations from 0.1% to 0.2%, the inhibition rate had reached 98.9%–99.9% when nitrapyrin concentration raised over 0.25%. The inhibition ability followed the order of nitrapyrin ≥ DMPP DCD. A significant impact of all three NIs on AOA and AOB community structure alteration was found, but there was no significant difference among the three inhibitors. The pakchoi above-ground weight, the contents of Vitamin C and amino acid were significantly improved by DCD, DMPP and nitrapyrin addition（P 0.05）, with the increase of pakchoi biomass of 12.7% with DCD, 11.1% with DMPP and17.6% with nitrapyrin, respectively.【Conclusions】Briefly, DCD, DMPP and nitrapyrin showed significant role in retarding nitrification in calcareous soil and exerted an obvious influence on AOA and AOB community structure（P〈0.05）. Comparatively, nitrapyrin was superior over DMPP and DCD on the soil inhibition, and the addition dose of 0.25% based on pure N was recommended for nitrapyrin application.