1.Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Key Laboratory of Original Agro-environment Pollution Prevention and Control of Ministry of Agriculture and Rural Affairs;2.Agricultural and Pastoral Bureau of Karakqin Banner, Chifeng, Inner Mongolia , China
Supported by the Fundamental Cutting-edge Projects of Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, China (No. 2021-jcqyrw-xwm), the Scientific and Technological Innovation Project of the Chinese Academy of Agricultural Sciences and the Special Fund for Scientific Research on Agricultural Public Causes of China (No. 201503121-04)
长期施用化肥所致的不利影响严重威胁到环境和人类的健康，已引起全世界的广泛关注。将生态友好的作物秸秆归还农田是减少化肥投入和缓解环境问题的极具潜力的农业管理措施。原生生物是土壤中丰富且多样的真核生物，是土壤微生物组的重要组成部分。为研究氮肥配施秸秆对原生生物群落的影响，设置了2 × 4（2个秸秆还田组×4个氮梯度）全因子交互田间定位试验，采用Illumina高通量测序技术研究了8种不同施肥处理下土壤原生生物群落多样性、组成和潜在功能的变化，并结合土壤理化性质分析探究驱动土壤原生生物群落变化的关键环境因子。结果表明：绿藻门（Chlorophyta）、锥足亚门（Conosa）、丝足虫门（Cercozoa）和纤毛虫门（Ciliophora）是所有处理中的优势类群。氮肥施用降低了土壤原生生物的多样性，而配施秸秆提升了土壤原生生物的多样性，并且在高施氮水平提升效果更为显著。绿藻门（Chlorophyta）的相对丰度随氮肥施用量增加呈下降趋势。丝足虫门（Cercozoa）和纤毛虫门（Ciliophora）的相对丰度在秸秆还田组中随氮肥施用量的增加而升高。捕食类原生生物（phagotrophs）在所有处理中均为绝对优势类群。与单施化肥处理相比，配施秸秆提高了捕食类原生生物的相对丰度，但降低了光养类原生生物（phototrophs）的相对丰度。单施化肥情况下，寄生类原生生物（parasites）表现出对高施氮量的偏好。土壤有机质和pH是土壤原生生物群落变化的重要驱动因子。总之，本研究证明了氮肥施用耦合秸秆还田措施能够影响土壤原生生物群落，同时明确了对农业管理措施变化反应敏感的原生生物类群。
Long-term chemical fertilization (especially nitrogen fertilization) under intensive land-management practices in agriculture is of great concern globally due to its adverse influence on the environment and human health. Returning the eco-friendly crop residues to farmland is a promising way of reducing chemical fertilizer input and alleviating environmental problems.【Objective】Protists are unicellular eukaryotes with enormous abundance and diversity, and play versatile functional roles to improve soil fertility and agricultural productivity. Thus, they comprise an integral component of soil microbiota in the agroecosystem. However, little is known about the responses of the soil protist community to nitrogen fertilization in combination with straw incorporation.【Method】Here, a fixed field trial with 2 × 4 full-factor interaction was performed to examine the variations in diversity, composition, and potential function of the protistan community using Illumina high-throughput sequencing under eight different fertilization treatments (2 straw returning groups × 4 nitrogen gradients)，Also, the key forces driving the variation in soil protistan community were determined in combination with edaphic property analysis.【Result】The phyla Chlorophyta, Conosa, Cercozoa and Ciliophora were dominant in the soils for all treatments. Nitrogen fertilization diminished the diversity of soil protists, whereas straw returning in general modified such impacts, with more pronounced effects under higher nitrogen application rates. Regardless of whether straw was added, the relative abundance of Chlorophyta exhibited an overall decrease with increased nitrogen gradient. Cercozoa and Ciliophora presented an increase in proportion with the amount of nitrogen fertilizer in the straw returning group. In the current study, the protistan functional community was predominated by phagotrophs in all treatments. Compared to treatments without straw addition, the implementation of straw returning enhanced the relative abundance of phagotrophs, but suppressed the proportion of phototrophs. Protistan parasites preferred a high nitrogen input under exclusive nitrogen fertilizer, with highest proportion in N300 treatment, which was significantly higher than those in all other treatments,. Soil properties were important environmental factors determining the shifts in soil protist community, with soil organic matter and pH exhibiting the most intensive influences as revealed by redundancy analysis (RDA) and Pearson’s correlation analysis.【Conclusion】This study provides experimental evidence that nitrogen fertilization coupled with straw incorporation have consequences for the soil protist community, It also shows that the phylogenetic and functional taxa of protists are responsive to such agricultural management regime alterations. Future studies should aim at deciphering the trophic associations among microorganisms, as well as constructing agricultural soil microhabitat beneficial for crops based on reasonable fertilization regimes and utilization of biotic resources like protists.
LI Shengjun, LI Yujie, ZHAO Jianning. Effects of Nitrogen Fertilization Combined with Straw Incorporation on Soil Protist Community[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202111090520,[In Press]