Liu Meixia, Zhao Xueqing, Hossain Md Elias, Wang Shangwen, Dong Wenyi, Gopalakrishnan Subramaniam, Liu Enke
Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502324, India.
Plants (Basel). 2022 Jun 30;11(13):1748. doi: 10.3390/plants11131748.
Soil extracellular enzymes are pivotal for microbial nutrient cycling in the ecosystem. In order to study the effects of different nitrogen application rates under plastic film mulching on soil extracellular enzyme activities and stoichiometry, five nitrogen application levels (i.e., 0, 90, 150, 225 and 300 kg·hm) were set based on two treatments: plastic film mulching (PM) and no film mulching (LD). We measured the soil extracellular enzyme activities (EEAs) and stoichiometry (EES) of four enzymes (i.e., β-1,4-glucosidase (βG), leucine aminopeptidase (LAP), β-1,4-N-acetylaminoglucosidase (NAG) and alkaline phosphatase (AP)) involved in the C, N and P cycles of soil microorganisms in surface soil at five maize growth stages (seedling stage, jointing stage, trumpet stage, grout stage and harvest stage). The results showed that there were significant differences in soil EEA at different maize growth stages. The soil nutrient content and soil EEA were significantly improved under PM, and the stoichiometric ratio of extracellular enzymes (E) was closer to 1:1:1, which indicated that PM was beneficial to the balance of soil nutrients and the activity of microorganisms. At each stage, with the increase in nitrogen application levels, the soil EEA showed a trend of increasing first and then decreasing (or remained unchanged), and both LD and PM treatments reached their highest activity at the 225 kg·hm nitrogen application rate. When the nitrogen application level was less than 225 kg·hm, the soil enzyme activity was mainly limited by the N nutrient, and when the nitrogen application level reached 300 kg·hm, it was mainly limited by the P nutrient. RDA and correlation analysis showed that the soil C:P, C:N, N:P and pH had significant effects on soil βG, NAG + LAP and AP activities as well as E, E and E.
土壤胞外酶对生态系统中微生物养分循环至关重要。为研究地膜覆盖下不同施氮量对土壤胞外酶活性及化学计量比的影响，基于地膜覆盖（PM）和无地膜覆盖（LD）两种处理设置了五个施氮水平（即0、90、150、225和300 kg·hm）。我们测定了五个玉米生长阶段（苗期、拔节期、喇叭口期、灌浆期和收获期）表层土壤中参与土壤微生物碳、氮和磷循环的四种酶（即β-1,4-葡萄糖苷酶（βG）、亮氨酸氨肽酶（LAP）、β-1,4-N-乙酰氨基葡萄糖苷酶（NAG）和碱性磷酸酶（AP））的土壤胞外酶活性（EEAs）和化学计量比（EES）。结果表明，不同玉米生长阶段土壤EEA存在显著差异。地膜覆盖下土壤养分含量和土壤EEA显著提高，胞外酶化学计量比（E）更接近1:1:1，这表明地膜覆盖有利于土壤养分平衡和微生物活性。在每个阶段，随着施氮量增加，土壤EEA呈先增加后降低（或保持不变）的趋势，LD和PM处理在施氮量为225 kg·hm时均达到最高活性。当施氮量小于225 kg·hm时，土壤酶活性主要受氮养分限制，当施氮量达到300 kg·hm时，主要受磷养分限制。冗余分析（RDA）和相关性分析表明，土壤C:P、C:N、N:P和pH对土壤βG、NAG + LAP和AP活性以及E、E和E有显著影响。
