旱作农田膜秸双覆盖耦合土壤解磷及固碳效应

Straw incorporation contributes significantly to the phosphorus (P) supply and its availability in dry-agricultural system. However, the coupling effect of plastic film mulch ridge-furrow tillage with topsoil straw incorporation on soil phosphorus availability and carbon sequestration in soil are not completely understood. For test these a 4–year fixed field experiment with chemical phosphorus and nitrogen fertilizer input plus topsoil straw incorporation is designed and planned to be conducted in dry alkaline phosphorus deficit soil in a semiarid region, Northwest China. The advanced techniques of modified soil phosphorus sequential extraction procedure, integrated physical and chemical carbon fractionation, Illumina CSPro-HiSeq high-throughput sequencing and ecosystem stoichiometric analysis method are employed to investigate the concentration of carbon and phosphorus pools and their turnover patterns; the activity of soil microbial, soil pH and alkaline (AlP) and acid phosphatase (AcP) involved in the P turnover as affected by the P dynamics in soil. Three aspects of questions on the characteristics of the soil phosphorus and carbon pools and their turnover patterns in crop-soil -microbial continuum caused by soil available phosphorus content changes, coupling phosphorus solubilizing mechanism of crop-soil pH- microorganisms in soil and soil carbon and phosphorus cycle stoichiometric feature are being systematic researched. The purpose is to reveal the regulation of soil carbon and phosphorus and their availability dynamics, the relationship between soil phosphorus content and carbon sequestration; the feature of soil pH, functional microorganism diversity and phosphatase activity and its coupling effect on soil available phosphorus. Furthermore, to clarify the biochemical and molecular ecology mechanism of soil phosphorus mobilization, soil carbon and phosphorus balance feature and phosphorus driving carbon sequestration effect. So that，to provide scientific support for regulation and controlling crop soil water consummation, chemical fertilizers application ratio and use efficiency and farmyard manure, crop straw and plastic film mulch patterns to reduce the negative effect of soil and rural environment pollution so as to boost green agriculture development.

针对旱作碱性土壤全膜双垄沟播与膜下耕层秸秆混入还田耦合对土壤磷解磷机制及其固碳效应这一科学问题，设置田间定位试验，采用不同形态磷顺序提取、有机碳物理-化学-粒径联合分级、微生物rDNA内转录间隔2区（ITS2）Illumina CSPro-Hiseq高通量基因测序、解磷酶活性分析、土壤pH动态分析和C:P生态化学计量分析等方法，开展作物-土壤-微生物连续体碳/磷库特征及其转化规律、作物—微生物—土壤pH—解磷酶耦合解磷机制和土壤碳磷循环特征研究；揭示土壤碳、磷组分含量及其有效性变化规律；土壤碳、磷含量变化的相关关系；有机添加驱动土壤pH+微生物+解磷酶活性特征及其解磷机制；阐明作物-土壤pH值-土壤微生物耦合磷活化的生化及分子生态学机理，作物—土壤—微生物连续体碳、磷元素含量平衡特征和磷驱动固碳效应。为“一控、两减、三基本”土壤面源污染防控，绿色农业增效发展提供科技支撑。

1999-2022年布置田间定位试验与大田辅助试验研究，探索旱作农田膜秸双覆盖耦合土壤解磷及固碳效应。结果表明，膜秸双覆盖显著提高0–40cm土层土壤有机碳（SOC））、土壤活性碳（LOC）、全量及有效氮磷钾（TN，TP, TK, AN, AP, AK）的含量及其贮量。加速SOC、LOC，TN，TP, TK, AN, AP, AK向0–60cm表层聚集。SOC及NPK养分层化指数（Stratification ratio）（即，0-5cm:5-10cm, 10-20cm, 20-40cm和40-60cm）多数大于2。显著改善土壤质量和肥力。膜秸双覆盖减氮控磷显著影响SOC, TP,AP，有机磷(Organic-phosphorus, OP), 无机磷(Inorganic phosphorus, IP), 易活性磷(LabileP), 中活性磷(Slow cycling P), 铁、铝结合态P(Fe-P 和AI-P)，以及碱性磷酸酶(Alkaline phosphatase, ALP) 和酸性磷酸酶(Acid phosphatase, ACP) 的含量。对闭蓄态磷(Occluded P)，结合磷(Bound phosphorus), 钙结合态磷(Ca-P)及树脂磷(Resin-P) 含量影响较小。特别明显地提高了SOC、TP、AP、及碱性磷酸酶(Phosphatase)的含量。磷素含量的增加对促进作物根系生长、下扎汲取土壤水分、养分，抗旱增产具有重要意义。膜秸双覆盖选择性地增加了厚壁菌门（Firmicutes）、芽单胞菌（Gemmatimonadetes）和酸菌门（Acidobacteria）的相对丰度。并促使三者加强正向合作，形成了一个有效的秸秆腐解功能群落。促进还田秸秆充分腐解、养分释放，因抵消了本土C,N,P，K矿化损失而显著提高土壤养分含量。减氮控磷显著提高Sphingomonas，Rhodospirillum，Nitrospira，Candidatus_Nitrosotenuis，Niastella 的丰度，明显提高Lysobacter，Chryseolinea， Bradyrhizobium 丰度。Sphingomonas（鞘氨醇单胞菌属，属变形菌门）具有强大的代谢降解许多芳香族化合物的能力，属磷溶解细菌，是调动作物磷营养的重要菌群； Nitrospira