Biochar can be a soil amendment that increases nutrient retention and carbon (C) sequestration in rice paddy systems. However, biochar can lose nutrient during its production processes so modifications such as coating with the nitrogen (N) that can slowly release nutrients to soil following application are necessary. Dynamic changes in paddy soil microbial communities affect the biogeochemical cycling of soil nutrients; however, the effects of addition of N-enriched biochar on paddy soil microorganisms and nutrient stoichiometry are unclear. Here, we investigated the effects of N-enriched biochar on soil bacteria and fungi community structure and on carbon (C), N, phosphorous (P), and iron (Fe) stoichiometry in subtropical paddy soils. The soil concentrations of TC, TN and TP increased by 0.27–18.55%, 1.31–18.15% and 10.35–54.24% respectively under the nitrogen rich biochar treatment. Under N-enriched biochar application, ratios of N/P and C/P decreased, while P-fixation capacity increased; the decrease in N/P ratio indicated that rice productivity was N-limited. The quantity of soil fungi increased by 42.07% and 10.89% in early and late rice, respectively in the treatment group applying 4t ha⁻¹ of N-enriched biochar. Relative abundance of the bacteria Bacillus, Geobacter, and Sideroxydans decreased with N-enriched biochar, whereas that of Thiobacillus and Thermomonas increased; relative abundance of the fungi Spicellomyces and Crustoderma increased with biochar. Relative abundance of the bacteria Bacteroides was negatively correlated with TC and Fe³⁺ (P < 0.05) and Sideroxydans and Geoyhrx was negatively correlated with soil TP (P < 0.05). Relative abundance of the fungi genera Westerdykella, Synchytrium, Russula, and Orbilia was positively correlated with soil TC (P < 0.05), Trapelia, Leptosphaerulina, and Tremella was positively correlated with soil TN (P < 0.05), and relative abundance of Leucanium, Monoblepharis was positively correlated with soil TP (P < 0.05). Overall, application of N-enriched biochar to paddy soils affected the microbial community composition through changes in soil physicochemical properties that led to shifts in microbial community function and associated improvements in soil nutrient enrichment.

Biochar 可以是一种土壤改良剂，可增加稻田系统中的养分保留和碳 (C) 封存。然而，生物炭在其生产过程中可能会失去养分，因此需要进行修改，例如涂上氮 (N)，以便在施用后缓慢地将养分释放到土壤中。水稻土微生物群落的动态变化影响土壤养分的生物地球化学循环；然而，添加富氮生物炭对稻田土壤微生物和养分化学计量的影响尚不清楚。在这里，我们研究了富含 N 的生物炭对土壤细菌和真菌群落结构的影响，以及对亚热带稻田土壤中碳 (C)、N、磷 (P) 和铁 (Fe) 化学计量的影响。TC、TN和TP的土壤浓度增加了0.27-18.55%、1.31-18.15%和10.35-54。在富氮生物炭处理下分别为24%。富氮生物炭施用下，N/P和C/P比降低，固磷能力增加；N/P 比的降低表明水稻生产力受氮限制。施用4t ha处理组早稻和晚稻土壤真菌数量分别增加42.07%和10.89%^-1的富含 N 的生物炭。Bacillus、Geobacter和Sideroxydans细菌的相对丰度随着富含 N 的生物炭而减少，而Thiobacillus和Thermomonas 的相对丰度增加；真菌Spicellomyces和Crustoderma 的相对丰度随着biochar增加。细菌拟杆菌的相对丰度与TC和Fe ³⁺呈负相关（P  < 0.05），Sideroxydans和Geoyhrx与土壤TP呈负相关（P  < 0.05）。真菌属的相对丰度Westerdykella、Syncytrium、Russula、Orbilia与土壤TC呈正相关（P  <0.05），Trapelia、Leptosphaerulina和银耳与土壤TN呈正相关（P  <0.05），Leucanium、Monoblepharis的相对丰度与土壤TC呈正相关TP( P < 0.05)。总体而言，将富氮生物炭应用于稻田土壤通过改变土壤理化特性影响微生物群落组成，从而导致微生物群落功能的变化和土壤养分富集的相关改善。