长期施肥下苹果园土壤团聚体特征及其稳定机制研究

Apple is the most important economic tree species in Northern China. In order to increase apple yield, the long-term application of excessive chemical fertilizers has brought a series of problems such as soil consolidation, soil acidification, soil quality decline and so on. Apple Orchard has the characteristics of concentrated fertilization position and fertilizer amount, and the centralized fertilization pattern of the apple orchard is completely different from that of the farmland. Soil aggregates are the basic unit of soil structure, so how to change the stability of soil aggregates in apple orchard under long-term fertilization and the mechanism of soil aggregate stability and its relationship with organic carbon transformation and composition are not clear. In order to find out the stabilization mechanism of soil aggregates under this special fertilization model, the soil of apple orchard under long-term fertilization experiment will be studied by long term fertilization experiment, pot experiment and laboratory culture experiment. Using synchrotron radiation microscopic CT and phospholipid fatty acid (PLFA) analysis, the differences of soil aggregate composition, pore structure and organic carbon composition in apple orchard under different fertilization conditions will be analyzed. The effect of centralized fertilization on aggregate stability of microzone soil will be investigated. The composition of microbial community which plays a key role in the mineralization of organic carbon with different particle size aggregates will be defined. The results will improve the understanding of soil aggregate response and organic carbon storage mechanism of apple orchard after fertilization, and provide theoretical support for rational fertilization, improving soil structure and sustainability of apple industry in apple orchard.

苹果是我国北方最重要的经济树种，果农为提高苹果产量，不断过量施用化肥导致土壤板结、酸化、土壤质量下降等问题。苹果园施肥位置集中且施肥量大，苹果园的集中施肥方式完全不同于农田。土壤团聚体作为土壤结构的基本单元，那么在长期施肥，尤其是集中施肥方式下苹果园土壤的团聚体含量、组成和孔隙结构如何变化，以及土壤团聚体稳定机制及其与有机碳转化和组成的关系均不清楚。因此，本项目以苹果园土壤为研究对象，通过长期定位试验、盆栽试验和室内培养试验，运用同步辐射显微CT和磷脂脂肪酸(PLFA)图谱分析等技术，分析不同长期施肥条件下苹果园土壤团聚体组成、孔隙结构特征和有机碳组分的差异；探明集中施肥方式对微域土壤团聚体稳定性的影响；明确各粒径团聚体有机碳矿化过程中起关键作用的微生物群落组成。研究结果将增进对苹果园施肥后土壤团聚体响应及其稳定性机制的了解，为苹果园合理施肥、改良土壤结构以及苹果产业的可持续提供理论支持。

施肥是影响土壤团聚体稳定性的重要因素。然而，苹果园集中施肥方式下，施肥对苹果土壤团聚体组成和稳定性的影响机制仍不明确。本研究以苹果园土壤为研究对象，通过盆栽试验、长期定位试验和室内培养试验，开展了以下三个方面的研究：（1）研究集中施肥方式下不同施肥处理对土壤团聚体形成和稳定性影响；（2）长期不同施肥措施下苹果园土壤团聚体稳定性及其影响因素；（3）不同施肥措施下苹果土壤各粒径团聚体有机碳转化过程。研究结果表明：（1）施用大颗粒活化腐植酸肥（LAF）能显著增加土壤水稳性大团聚体含量和提高土壤团聚体稳定性，全量施用LAF提高效果最显著；化肥减施各处理虽能提高土壤水稳性大团聚体含量和稳定性，但提升效果不显著。（2）施LAF能显著提高土壤各粒径团聚体有机碳含量，提高土壤大团聚体有机碳贡献率。（3）施LAF能显著提高苹果产量，提高土壤有机碳和速效养分含量。相关分析表明，土壤团聚体稳定性指标与土壤总孔隙度、有机碳、硝态氮、铵态氮、有效磷、速效钾呈极显著正相关，与土壤容重呈极显著负相关。（4）全量施LAF处理能显著提高土壤有机碳累积矿化量，不同施肥处理下土壤大团聚体有机碳累积矿化量显著高于微团聚体。本研究结果可为全面理解土壤团聚体稳定性机制、苹果园合理施肥提供理论依据。