潮土团聚体对磷素转化与蓄供过程的作用机制研究

Phosphorus (P) is the most important limiting element of fluvo-aquic soil in the Huang-Huai-Hai Plain. To achieve high yields, a lot of P fertilizers have to be applied into soils in this region. Thus, it is very important to improve P availability in fluvo-aquic soil for agricultural production in this region. The previous researches has demonstrated that increasing soil aggregation can promote phosphorus activation, however, its mechanism is still unclear. Based on long-term fertilization experiment and conservation tillage experiment, a series of laboratory control and culture experiments will be conducted in this proposed project. Some modern methods and techniques such as oxygen isotope of phosphate and 31P nuclear magnetic resonance spectroscopy will be applied to quantify P forms and storage in the different fractions of soil aggregates, to investigate the effect of soil aggregates on P adsorption-desorption and mineralization-immobilization processes and the long-term cycle path of P, and to build up the relationship between soil aggregate properties and P dynamics and find the drive factors of the P transformation. The aim of this study is to elucidate the influence mechanism of aggregate on P availability and transformation in fluvo-aquic soil and to provide theoretical basis and technical support for the soil fertility cultivation and agricultural P management in the Huang-Huai-Hai Plain.

磷素是黄淮海平原潮土区的重要限制营养元素，该区域一直依靠磷肥的大量投入来维持高产，因此，提高潮土磷素有效性对黄淮海平原农业生产至关重要。研究证明提升土壤团聚化水平可促进磷素活化，但其作用机制尚不明确。本项目以中国科学院封丘农业生态试验站肥料长期试验和耕作与秸秆还田长期试验为平台，通过田间试验和室内控制培养实验相结合，借助磷酸盐氧同位素、31P核磁共振波谱等技术手段，定量解析不同粒级团聚体对潮土磷素形态和蓄供的贡献；探索不同团聚体对磷素吸附解吸、矿化固定过程的影响；深入研究不同团聚体对磷素长期循环路径的作用机制；分析团聚体孔隙及理化特性与磷素转化过程的关系，明确潮土磷素转化过程的驱动因子。以期阐明潮土团聚体对磷素有效性及其循环过程的作用机制，为黄淮海平原地区土壤地力培育和农田磷素管理提供理论基础和技术支持。

提高潮土磷素有效性对黄淮海平原农业生产至关重要，研究证明提升土壤团聚化水平可促进磷素活化，但其作用机制尚不明确。本项目以中国科学院封丘农业生态试验站肥料长期试验和耕作与秸秆还田长期试验为平台，研究潮土团聚体对磷素转化与蓄供过程的作用机制。结果表明：有机肥部分或全部替代化肥可以改善土壤团聚结构，同时提高了活性无机磷库、磷酸单酯和磷酸二酯的含量，从而提高了磷的供应能力。少免耕和秸秆还田显著增加了大团聚体中活性磷库的磷含量，进而提高磷素有效性。通过磷素等温吸附解吸试验，阐明了物理结构和化学性质共同影响着不同管理措施下潮土的磷素吸附解吸过程。保护性耕作和有机肥施用促进了土壤有机质和磷素的累积，降低了土壤pH和Al氧化物含量，同时改善了团聚体结构，进而促进了磷素释放。通过外源活性有机物料矿化培养试验，明确了微生物群落改变特别是真菌和细菌之间的相互作用主导了不同团聚化潮土磷素矿化固定过程。采用磷酸盐氧同位素标记室内培养试验，研究了长期不同施肥条件下潮土的磷素长期循环路径，证实了生物转化过程是化肥磷在潮土中主要转化途径，且有机质含量高、团聚体结构好的土壤生物作用在化肥磷转化过程中的贡献更高。本项目初步阐明了潮土团聚体对磷素有效性及其循环过程的作用机制，为黄淮海平原地区磷素管理提供了科学依据。