滨海盐碱地不同棉花秸秆还田量和深松对棉花产量形成的调控机理

Straw returning and subsoiling are important practices in soil amelioration, and directly influence crop growth and yield. Salinity is a major limiting factor for higher cotton productivity. However, in the perspective of reducing soil salinity and improving soil fertility, we have little knowledge on regulation mechanism of yield formation when cotton straw is fully or partially returned to the field in relation to a deep tillage practice in Coastal Saline-alkali Region. The objectives of this research are to quantify soil salinity and nutrient dynamics and distribution; and to address the regulation mechanism of root morphology on soil salinity and nutrient distribution; and to quantify accumulation and distribution of salinity and nutrient in cotton; and to quantitatively explore photosynthesis, dry matter accumulation and partitioning, and to address the mechanism of crop growth and yield formation in relation to returning different amount of cotton straw and subsoiling. To do so, field experiments are conducted to determine the soil physical properties, spatial and temporal distribution of soil salinity and nutrient, dynamics of salinity and nutrient of absorption and distribution in cotton growth stages, root growth and morphological traits, leaf photosynthesis traits, dry matter accumulation and distribution with cotton straw returning and subsoiling under coastal saline-alkali soil. The results would provide a theoretical basis and technical support for soil amelioration and yield improvement of cotton in Coastal Saline-alkali Region.

秸秆还田和深松均是土壤改良的重要措施，影响作物生长和产量。盐分是限制滨海盐碱地棉花高产的关键因素，但是，从降低土壤含盐量和提高肥力的角度，采用棉花秸秆还田系统研究该地区秸秆还田量和深松对棉花产量形成的调控机理尚缺乏。本项目拟通过对滨海盐碱地试验田棉花秸秆还田量和深松下土壤物理性质、土壤盐离子和养分分布特征以及被棉株吸收后的积累分配动态、根系生长和形态、叶片光合特性和干物质积累分配动态的研究，阐明不同秸秆还田量和深松对土壤结构的影响规律，揭示根系形态对土壤盐离子、养分分布的调控机制，明确棉株体内盐离子和养分的积累分配规律，明确棉花光合产物积累和分配动态规律，从而揭示秸秆还田量和深松对棉花产量形成的调控机理。这方面的研究结果将为滨海盐碱棉区的土壤改良和棉花高产提供理论依据和技术支撑。

棉花是盐碱地改良的大田先锋作物，随着粮棉争地矛盾加剧，内陆棉花种植逐渐向滨海盐碱地集中。针对滨海盐碱地盐离子和养分失衡的特点，如何有效降低棉田含盐量和提高土壤肥力，是减轻棉花盐害和实现高产的关键。秸秆还田和深松是土壤改良的重要措施，影响作物生长和产量。但是，采用棉花秸秆还田，系统研究该地区秸秆还田量和深松对棉花产量形成的调控机理尚缺乏。本项目通过对滨海盐碱地试验田棉花秸秆还田量和深松下土壤物理性质、土壤盐离子和养分分布特征以及被棉株吸收后的积累分配动态、根系生长和形态、叶片光合特性和干物质积累分配动态的研究，揭示了秸秆还田量和深松对棉花产量形成的调控机理。通过研究发现：秸秆还田和深松主要通过增加铃数、铃重和养分利用效率进而增加棉花产量；秸秆还田降低0-20cm土层土壤容重，增加了大团聚体含量，深松降低20-40cm土层土壤容重；秸秆还田降低0-20cm土层土壤pH、含盐量、Na+、Cl-含量，深松降低20-40cm土层土壤容重、Na+、Cl-含量；秸秆还田增加0-40cm土层土壤根系生物量、根系总根长、根表面积和根体积，深松改变了20-40cm土层中根系形态特征；秸秆还田增加群体光合速率、生殖器官干物质积累分配、养分吸收、K+、Ca2+含量，降低Na+、Mg2+含量；深松增加了棉花花铃期叶片中Na+含量，降低了苗期、蕾期和初花期茎枝的Mg2+含量。我们的研究结果表明，棉花秸秆全量还田配合深松具有提高棉花产量的潜力，在滨海盐碱区域可以作为一项有效的应用措施，从而为滨海盐碱棉区的土壤改良和棉花高产提供理论依据和技术支撑。