Despite the well-documented role of biochar in promoting soil quality and crop productivity, the underlying biological mechanisms remain poorly understood. Here, we explored the effects of straw biochar on soil microbiome in the rhizosphere from wheat using metagenomic sequencing. Our results showed that straw return decreased the yields of wheat, while the straw biochar return increased the wheat yields. Further, both the richness and community composition confirmed different effects of the straw return and straw biochar return. The straw biochar return also resulted in greater rhizosphere effects from wheat, represented by resource availability, including soil organic carbon, soil total nitrogen, available phosphorus, and available potassium. The rhizosphere effects from wheat, represented by microbial metabolism genes involved in carbon, nitrogen, phosphorus, and potassium cycling, however, were decreased by straw biochar returning. In addition, the rhizosphere effects from nitrogen content and the nitrogen cycling genes showed negative relationships with wheat yields. Together, these results revealed that straw biochar enhanced soil resource availability but suppressed microbial metabolism genes in the rhizosphere from wheat, supporting the idea that straw biochar serves as a nutrient pool for crops.

秸秆还田是提高作物氮肥利用率的有效途径之一.但由于作物的氮肥利用率受到环境条件和管理方式的影响,且多数研究只在某一特定区域或条件下进行,对于全国不同区域秸秆还田对氮肥利用率影响的研究缺乏系统分析和比较.为了探明我国农田主要粮食作物氮肥利用率对秸秆还田的响应及其关键调控因素,基于 77份文献的数据,开展了整合分析(Meta-analysis).结果表明,与秸秆不还田相比,秸秆还田条件下NUE(氮肥利用率)和PFPN(氮肥偏生产力)的效应值分别显著增加 10.0%和 6.14%(P<0.05).秸秆还田方式是影响NUE效应的关键调控因子,覆盖还田NUE提升幅度是翻压还田提升幅度的 2倍左右.土壤全氮、土壤酸碱性及气候类型是秸秆还田调控PFPN的关键因子.当土壤全氮含量>1.25 g·kg-1 或在中性土壤条件下时,PFPN提升幅度显著高于该因子的其他水平.在亚热带季风气候和温带季风气候条件下,秸秆还田对PFPN提升效果显著.回归分析发现,秸秆还田对PFPN的影响因土壤全氮含量上升而提高(P<0.05);随土壤pH的增加而先上升后下降;年均温和降雨量与PFPN之间均呈非线性相关关系(P<0.000 1).秸秆还田可以显著提高我国主要粮食作物的氮肥利用率,但不同表征指标对于秸秆还田的响应程度及其关键调控因素存在显著差异.

为探明安徽沿淮地区麦秆粉碎还稻田时配施不同的腐秆剂对土壤养分以及活性有机碳的影响,遴选出适合该区域使用的腐秆剂,通过安徽省霍邱县的秸秆促腐还田定位试验,比较了秸秆还田+优化平衡施肥+不施腐秆剂(SF)、秸秆还田+优化平衡施肥+腐秆剂 1 号(SFD1)、秸秆还田+优化平衡施肥+腐秆剂 2 号(SFD2)和秸秆还田+优化平衡施肥+腐秆剂 3 号(SFD3)4 个处理在耕层土壤养分、总有机碳、活性有机碳、微生物生物量碳、不同形态碳素有效率和碳库管理指数等方面的差异.结果表明,配施腐秆剂处理中SFD1 和SFD2 的土壤碱解氮含量显著高于不施腐秆剂处理SF(P<0.05),分别增加了 14.3%和 15.6%;SFD1 和SFD2 处理较SF处理活性有机碳、微生物生物量碳、活性有机碳有效率和微生物生物量碳有效率分别显著提高了 18.8%、48.0%、6.5%、33.3%和 18.0%、51.0%、5.2%、37.5%(P<0.05),SFD3 较SF处理微生物生物量碳及有效率显著降低了 52.2%和 41.7%(P<0.05);配施腐秆剂SFD1 和SFD2 处理的土壤碳库管理指数(CPMI)值整体显著高于不施腐秆剂处理SF,均增加了 22.4%(P<0.05);土壤总有机碳能够表征土壤养分及碳素动态变化.综上可知,安徽沿淮稻田秸秆还田配施1 号或 2 号腐秆剂均有利于提高土壤养分,提升土壤碳库管理指数.

Although straw-decomposing microbial inoculants (SDMI) are capable to generally promote the fertility of straw-amended soils, their impact on the release of individual soil major nutrients remains controversial. Additionally, the combined effects of SDMI and environment/management on various forms of nutrients remain poorly documented. To fill these research gaps, we conducted a meta-analysis study using 1214 paired observations from 132 field trials in China. Our results showed that SDMI significantly increases the total and available concentrations of nitrogen, phosphorus, and potassium in soil (p < 0.05), although increases in nutrients varied with different conditions. Moreover, mean annual precipitation (MAP) had significant correlations with the effects of SDMI-amended straw on soil total nitrogen (p = 0.008) and available nitrogen (p = 0.0006). The effect of SDMI-amended straw on soil total phosphorus and soil available potassium was mainly correlated with soil organic matter (p = 0.032) and MAP (p = 0.049), respectively. Our findings indicate that SDMI-amended straw can have a measurable impact on the status of soil major nutrients. In particular, the application of SDMI-amended rice straw with an initial C/N ratio of ≤15 to neutral soils in temperate and subtropical monsoon climates is a promising strategy.