不同浓度石灰氮对黄瓜连作土壤微生物生物量及酶活性的影响

为分析比较不同浓度石灰氮对连作黄瓜田土壤环境的作用效果，通过2年温室定位试验，在黄瓜秸秆还田的基础上以不施石灰氮为对照(CK)，研究施用\高浓度石灰氮1350 kg·hm^-2(CaCN₂ 90)、中浓度石灰氮900 kg·hm^-2(CaCN₂ 60)、低浓度石灰氮450 kg·hm^-2(CaCN₂ 30)\]对连作黄瓜土壤微生物生物量碳(SMBC)、微生物生物量氮(SMBN)及酶活性的影响.结果表明：与其他处理相比，CaCN₂ 90显著降低苗期0～10 cm 土层SMBC，但增加了初瓜期后0～20 cm土层SMBC.施用石灰氮处理均显著提高了末瓜期0～20 cm土层SMBC及盛瓜期至末瓜期0～10 cm土层SMBN，但第1年（2012年）不同石灰氮用量间无明显规律，第2年(2013年)盛瓜期后SMBN随着石灰氮施用浓度的增加而升高.施用石灰氮有利于秸秆的腐熟，提高土壤有机质含量，且石灰氮浓度越高越有利于秸秆的腐熟.相比对照，施用石灰氮能有效提升土壤脲酶、过氧化氢酶和多酚氧化酶活性，其中脲酶活性随石灰氮浓度的增加升高，而多酚氧化酶活性随石灰氮浓度的增加而降低，CaCN₂ 60可有效提高过氧化氢酶活性.相关分析表明：土壤有机质、脲酶及过氧化氢酶活性与SMBC、SMBN呈极显著正相关，多酚氧化酶活性与SMBC、SMBN呈显著负相关.表明黄瓜秸秆还田后施用石灰氮900 kg·hm^-2能够改善温室黄瓜连作田土壤环境，有效减缓温室黄瓜连作障碍.

Effects of different application rates of calcium cyanamide on soil microbial biomass and enzyme activity in cucumber continuous cropping.

A 2 year field experiment was conducted to study the effects of CaCN₂ combined with cucumber straw retention on soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN) and soil enzyme activities under cucumber continuous cropping system. Four treatments were used in this study as follows: CK (null CaCN₂), CaCN₂ 90 (1350 kg CaCN₂·hm^-2), CaCN₂ 60 (900 kg CaCN₂·hm^-2), CaCN₂ 30 (450 kg CaCN₂·hm^-2). The results indicated that, compared with the other treatments, CaCN₂ 90 treatment significantly decreased SMBC in 0-10 cm soil layer at seedling stage, but increased SMBC in 0-20 cm soil layer after early fruit stage. Compared with CK, CaCN₂ increased SMBC in 0-20 cm soil layer at late fruit stage, and increased SMBN in 0-10 cm soil layer at mid and late fruit stages, however there was no significant trend among CaCN₂ treatments in the first year (2012), while in the second year (2013) SMBN increased with the increasing CaCN₂ amount after mid fruit stage. CaCN₂ increased straw decaying and nutrients releasing, and also increased soil organic matter. Furthermore, the CaCN₂ 90 could acce lerate straw decomposition. Compared with CK, CaCN₂ effectively increased soil urease, catalase and polyphenol oxidase activity. The soil urease activity increased while the polyphenol oxidase activity decreased with the increase of CaCN₂, and CaCN₂ 60 could significantly improve catalase activity. Soil organic matter, urease activity and catalase activity had significant positive correlations with SMBC and SMBN. However, polyphenol oxidase activity was negatively correlated to SMBC and SMBN. Our findings indicated that CaCN₂ application at 900 kg·hm^-2 combined with cucumber straw retention could effectively improve soil environment, alleviating the soil obstacles under the cucumber continuous cropping system.