State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China; Laboratory of Integrated and Urban Phytopathology, Gembloux Agro-Bio Tech, University of Liège, Passage des déportés 2, 5030 Gembloux, Belgium; National Center of Technology Innovation for Comprehensive Utilization of Saline-Alkali Land, Innovation for Comprehensive Utilization of Saline-Alkali Land, Shandong 257000, China.
State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China; National Center of Technology Innovation for Comprehensive Utilization of Saline-Alkali Land, Innovation for Comprehensive Utilization of Saline-Alkali Land, Shandong 257000, China.
Sci Total Environ. 2024 Nov 10;950:174933. doi: 10.1016/j.scitotenv.2024.174933. Epub 2024 Jul 21.
Root exudation and its mediated nutrient cycling process driven by nitrogen (N) fertilizer can stimulate the plant availability of various soil nutrients, which is essential for microbial nutrient acquisition. However, the response of soil microbial resource limitations to long-term N fertilizer application rates in greenhouse vegetable systems has rarely been investigated. Therefore, we selected a 15-year greenhouse vegetable system, and investigated how N fertilizer application amount impacts on root carbon and nitrogen exudation rates, microbial resource limitations and microbial carbon use efficiency (CUE). Four N treatments were determined: high (N3), medium (N2), low (N1), and a control without N fertilization (N0). Compared to the control (N0), the results showed that the root C exudation rates decreased significantly by 42.9 %, 57.3 % and 33.6 %, and the root N exudation rates decreased significantly by 29.7 %, 42.6 %, and 24.1 % under N1, N2, and N3 treatments, respectively. Interactions between fertilizer and plant roots altered microbial C, N, P limitations and CUE; Microbial C and N/P limitations were positively correlated with root C and N exudation rates, negatively correlated with microbial CUE. Random Forest analysis revealed that the root C and N exudation rates were key factors for soil microbial resource limitations and microbial CUE. Through the structural equation model (SEM) analysis, soil NH content had significant direct effects on the root exudation rates after long-term N fertilizer application. An increase in root exudation rates led to enhanced microbial resource limitations in the rhizosphere soils, potentially due to increased competition. This enhancement may reduce microbial carbon use efficiency (CUE), that is, microbial C turnover, thereby reducing soil C sequestration. Overall, this study highlights the critical role of root exudation rates in microbial resource limitations and CUE changes in plant-soil systems, and further improves our understanding of plant-microbial interactions.
根系分泌物及其介导的氮（N）肥料驱动的养分循环过程可以刺激各种土壤养分的植物可利用性，这对微生物养分获取至关重要。然而，温室蔬菜系统中长期施用氮肥对土壤微生物资源限制的响应很少被研究过。因此，我们选择了一个 15 年的温室蔬菜系统，研究了 N 肥施用量如何影响根系碳和氮的分泌率、微生物资源限制和微生物碳利用效率（CUE）。确定了四种 N 处理：高（N3）、中（N2）、低（N1）和不施 N（N0）的对照。与对照（N0）相比，结果表明，N1、N2 和 N3 处理下，根系 C 分泌率分别显著降低了 42.9%、57.3%和 33.6%，根系 N 分泌率分别显著降低了 29.7%、42.6%和 24.1%。肥料和植物根系之间的相互作用改变了微生物 C、N、P 的限制和 CUE；微生物 C 和 N/P 限制与根系 C 和 N 的分泌率呈正相关，与微生物 CUE 呈负相关。随机森林分析表明，根系 C 和 N 的分泌率是土壤微生物资源限制和微生物 CUE 的关键因素。通过结构方程模型（SEM）分析，长期施氮后，土壤 NH 含量对根系分泌率有显著的直接影响。根系分泌率的增加导致根际土壤中微生物资源限制增强，这可能是由于竞争加剧所致。这种增强可能会降低微生物碳利用效率（CUE），即微生物 C 的周转，从而减少土壤 C 的固存。总的来说，本研究强调了根系分泌率在植物-土壤系统中微生物资源限制和 CUE 变化中的关键作用，并进一步提高了我们对植物-微生物相互作用的理解。
