“苗带紧行间松”合理耕层土壤结构特征及其调控机制

It is well known that soil structure is the basis of soil function and influenced on it. However, the aims of soil tillage create good structures and motivate the function advantages in order to offer the comfortable soil environments for the growth of crop roots by means of adopting the optimal tillage methods. Therefore, the crop growths are enhanced and the crop yields are improved because of heath roots in soil environment. Meanwhile, the soil is protected for the views of sustainable agricultural development.. At present, available soil tillage layers become shallow, tillage pan layers become hardness, soil quantity is significantly reduced, black soil layer become thinner and thinner, soil organic matter is declined quickly, soil quality is lower and lower and make soil keep soil water and fertilizer worse. For those reasons, soil qualities are declined, soil structures are damaged and functions are disappeared. Those conditions produce adverse effect on the crop growth and restrained the increase of yield. However, the best way to solve the problem is that the optimal tillage layer structure is designed and created through adopting the good and benefit tillage method.. The objectives of our experiment will assess the soil structure characteristics under compact seedbed and loose ridge furrow alternative tillage (CSLRFAT) through the Micro area experiment, located experiment and field experiment by means of adopting the CT and SRμ-CT Scan Devices. The relationship of soil structure, physical and chemical properties and root characteristics will be studied. The mechanisms of tillage layer regulated under CSLRFAT will be revealed from the views of soil structure and function. Mechanisms of soil structure-function-root interaction will be revealed on basis of the system experiments. The study results will offer the theoretical basis for constructing the optimal tillage layers and designing the useful tillage methods. Meanwhile, those will offer the scientific basis for enhancing the sustainable agricultural development.

土壤结构是土壤功能的基础，决定土壤功能。而土壤耕作的目的是通过采取合理的耕作方式创造良好的土壤结构，充分发挥土壤功能优势，为根系提供良好的生长环境，进而促进作物生长发育，提高作物产量，同时保育土壤。但目前东北生产上长期由于不合理的耕作方式导致土壤耕层“浅、实、少、薄、低、弱”，土壤“体质”下降，结构恶化，功能失衡，影响作物生长发育，制约产量的提高。然而，通过耕作措施创建合理耕层结构是解决这一问题的有效途径之一。本研究通过微区试验（人工模拟）、定位试验（1983年）和大田试验，采用医用CT和SRμ-CT分别扫描土体和团聚体结构，深入研究“苗带紧行间松”耕层土壤结构特征，明确与土壤理化性质及根系生长特性之间的关系，从土壤结构与功能层面揭示其对耕层调控作用，进一步探明土壤结构—功能—根系之间的互作机理，为构建合理耕层结构与创制适宜的耕作方法提供理论基础，为促进农业的可持续发展提供科学依据。

东北是我国重要的粮食生产基础，但经过长时间不合理的耕作管理后，出现了水土流失、土壤结构退化等问题，严重影响土壤生产力能的发挥和高效生产。特别是传统翻耕破坏了土壤结构，恶化了土壤养分和水分运移与传导，形成了不利于作物生长的土壤环境。因此，本项目依托长期定位试验，采用大田试验与微区模拟相结合的方法，运用现代CT扫描技术，通过原位静压法，分析了原始土体的孔隙度、孔隙分布及微结构形成特征，探明了0-30cm原状土体结构特征，发现0-30cm原状土体结构免耕处理的孔隙数量最少，而孔隙大多为土壤动物（特别是蚯蚓）和植物根系形成的粗大孔隙；揭示了1-2mm团聚体内部孔隙度、孔隙分布及微结构形成特征，探明了1-2mm团聚体结构特征为免耕最优。 同时，通用皮尔森相关分析表明不同粒径团聚体有机碳与土壤有机碳均存在极显著相关性，而且2-1mm和1-0.25mm粒级是有机碳贮存的主要场所，也是土壤碳库饱和的重要指标，对土壤有机碳的积累和富积具有重要的贡献，对土壤碳库的平衡起关键作用。而且，进一步证实了0.25-1mm、1-2mm团聚可以作为指示耕作方式对团聚体特征长期影响的指标，分形维数（D）也可作为评估土壤团聚体稳定性的较好指标。此外，阐明验证了“苗带紧行间松”耕作调控土壤环境，改善土壤物理性质，提高土壤养分含量，丰富土壤微生物数量，降低土壤呼吸速率，提高土壤中稳定性大团聚体的数量，增强土壤结构稳定性，促进土壤有机碳的积累和富积，对土壤碳库的平衡起关键作用。同时，本研究表明深松耕作提高土壤含水量促进保苗率提高12.7%，促进苗期生长发育，改善茎部性状，提高根系生长质量，优化作物冠层结构，改善植株生理状况延缓衰老，提高叶片光合能力，促进生育期间干物质的积累，产量显著提高15.0%。另外，本研究重点解析了土壤结构、功能与根系之间的关系及其互作机制，而且明确“苗带紧行间松”耕作优化了耕层结构，有效解决耕层构造与作物多样性需求间的矛盾，为东北农田合理耕层构建提供了理论支撑。