渭北旱塬粮田长期保护性轮耕的土壤固碳减排效应与微生物多样性响应机制

Little rainfall and low soil fertility are main restraints of grain production on Weibei highland. Conservation tillage of dryland grain field can improve soil ecology, enhance soil fertility and cropland quality, and contribute to realize the strategy of “store grain in the land”. At present, most researches of conservation tillage on dryland grain field are about the effects of drought resistance and increase production, but mechanism of soil ecological effects of soil carbon and nitrogen content, microbial diversity and green house gas emission under long-term rotational conservation tillage on dryland grain field of Weibei highland are still lack systematic study. A long-term field experiment of rotational conservation tillage and fertilization on rainfed grain fields (which with cropping systems of winter wheat continuous cropping, spring maize continuous cropping and wheat-maize rotation separately) of Weibei highland, Shaanxi province, will be continuously conducted. The soil carbon and nitrogen content, microbial diversity and green house gas emission under different rotational conservation tillage patterns (which combined with no-tillage or subsoiling with crop residure mulching, and deep plowing with crop residure buried into soil) will be observed and measured. The mechanism of effects of crop rotation, rotational soil tillage and chemical fertilizer on soil microbial diversity, carbon sequestration and emission reduction on dryland grain fields will be analyzed. Based on exploration of soil ecological effects and soil fertility improvement of rotational conservation tillage, the optimal rotational patterns of conservation tillage for quality improvement of grain fields will be chosen, and it can supply scientific foundation for improvement of soil fertility and sustainability of yield increase on dryland grain fields of Weibei highland.

干旱少雨和土壤瘠薄是渭北旱塬粮田增产的主要制约因素。保护性耕作能够改善旱作粮田土壤生态，提升土壤肥力与耕地质量，有助于实现“藏粮于地”战略。目前，对旱作粮田保护性耕作抗旱增产效应研究较多，但对长期保护性轮耕下“微生物群落演变—土壤碳氮转化—温室气体排放”的土壤生态机理研究较少。延续渭北旱塬冬小麦连作田、春玉米连作田和麦玉轮作田长期保护性轮耕与施肥定位试验，研究不同保护性轮耕模式（秸秆覆盖免耕、秸秆覆盖深松和秸秆还田翻耕三者组合）下土壤碳氮含量、土壤微生物多样性和温室气体排放规律，分析作物轮作、土壤轮耕和化肥配施对粮田土壤微生物多样性与固碳减排效应的影响机制，揭示旱作粮田保护性轮耕模式的土壤生态效应和土壤培肥规律，筛选有助于耕地质量提升的最优保护性轮耕模式，能为渭北旱塬粮田土壤培肥和持续增产提供科学依据。

为了探明渭北旱作粮田长期保护性轮耕的土壤生态机理，揭示不同保护性轮耕模式的土壤固碳减排效应和微生物驱动机制，基于2007-2020年陕西渭北旱塬合阳县冬小麦连作田、春玉米连作田和麦玉轮作田长期保护性耕作与施肥定位试验，系统研究了由秸秆覆盖免耕、秸秆覆盖深松和秸秆还田翻耕等耕作措施组成的不同保护性轮耕模式和不同施肥方式下粮田土壤碳氮含量变化、微生物多样性与功能种群差异、土壤温室气体排放特征。通过对不同处理粮田土壤剖面碳氮含量测定、土壤细菌16SrDNA扩增子测序和宏基因组测序分析、田间温室气体静态箱采样与气相色谱法分析，结果表明：（1）“免耕-深松轮耕”模式能显著提高冬小麦连作田0-100 cm土层有机碳储量和0-30 cm土层速效氮含量，提高了土壤细菌多样性和碳代谢相关物种的丰度，降低土壤CO2和N2O排放量；（2）“免耕-免耕-深松轮耕”模式能显著提高春玉米连作田0-20 cm土层有机碳含量和全氮含量，提高了土壤细菌多样性和丰富度指数，驱动了与碳氮转化相关的功能微生物的丰度，同时降低了CO2和N2O的排放量；（3）“连续免耕”和“翻耕-免耕轮耕”模式分别显著提高了麦玉轮作田0-20cm和20-40 cm土层土壤有机质和全氮含量，显著增加了土壤细菌固碳相关物种，增强了土壤碳固定能力，降低了碳排放速率；（4）在3类粮田中，玉米连作田0-20cm土壤有机碳含量和细菌α-多样性最高，能有效降低周年CO2和N2O排放量。所筛选出的固碳减排型保护性耕作轮耕模式，为渭北旱塬粮田绿色可持续生产提供了科学依据。项目执行期间，发表期刊论文20篇和会议论文1篇，其中SCI论文15篇，EI论文1篇；培养研究生9人，其中博士生4人。