赤红壤常年菜地磷库特征及供磷机制研究

Research will be conducted in the perennial vegetable field system in latosolic red soil zone. Soil phosphorus speciation in vegetable field will be analyzed by using chemical fractionation technique in combination with solution 31P nuclear magnetic resonance (NMR) spectroscopy and the labile phosphorus form will be revealed. Phosphorus supply potential and capacity will be evaluated through the conversion process of organic phosphorus mineralization, adsorption and desorption and diffusion of inorganic phosphorus in bulk soil and the rhizosphere based on laboratory incubation experiment and pot experiment. The X-ray diffraction will be used to identify the mineral type and composition of soil. Furthermore, relationship between phosphorus (distribution, conversion and diffusion of different phosphorus speciation) and the main soil properties (e.g. oxide of Fe, Al and Mn as well as other physicochemical properties) will be established and the dominant influencing factors will be recognized. Results obtained above-mentioned can contribute to elucidate the characteristics of phosphorus pool and its supply mechanisms, which will provide scientific basis for phosphorus efficient use in vegetable field of latosolic red soil zone.

以赤红壤常年菜地系统为研究对象，采用连续提取和液体核磁共振波谱技术（31P NMR）分析土壤有机、无机磷含量和形态分布，明确土壤活性磷赋存形态；基于室内培养和盆栽试验研究土壤有机磷矿化、无机磷吸附、解吸等形态转化特征及磷在根-土界面扩散特点，评价土壤磷供应潜力和供应能力；结合土壤矿物类型和成份的X射线衍射表征结果，系统分析土壤铁、铝、锰氧化物及主要理化性质与磷形态分布和转化及磷迁移之间关联性，探明影响赤红壤磷赋存和供应的主要土壤因子，揭示赤红壤磷库特征及供磷机制，为赤红壤区菜地磷素高效利用提供科学依据。

常年菜地具有化肥施用量大、种植茬数多、周年生产等特点，加之广东地带性赤红壤富含铁铝氧化物，导致赤红壤常年菜地成为磷素面源污染高风险区。研究阐明菜地土壤磷库特征及其供磷机制，有助于制定更为精确的磷素养分管理方案，从而为降低区域菜地面源污染提供理论依据。本项目采集大量常年菜地土壤样品(190份）基础上，结合室内培养试验，采用土壤磷素连续分级提取和31PNMR分析技术、定量PCR方法及扫描电镜能谱（SEM-EDS）分析，探明了赤红壤常年菜地土壤全磷和有效磷盈余现状，明确了菜地土壤磷以无机磷为主要赋存形态，生物有效性高的活性磷占比较高（平均占总磷含量25%）、中等活性磷和有机磷是潜在有效磷供应源等磷库基本特征，阐明了土壤全磷、络合态和游离态铁氧化物、有机质、CaCO3含量和电导率等是影响活性磷含量的直接作用因子。探究了土壤残留磷的矿化潜力和外源氮对残留磷矿化的促进效应以及土壤具有吸附能力强、解吸能力弱的特点，明确了土壤pH值、磷酸酶活性等是影响土壤磷转化的主要因素。研究明确土壤残留磷扩散主要发生在培养的前10天内、施磷显著提高土壤磷的扩散量及扩散持续时间等特点；研究发现了根际土壤水溶性磷低于非根际土壤的分配特点及施磷增加根际和非根际土壤磷生物有效性、降低非根际土phod基因丰度，明确了土壤pH值、有效磷、水溶性磷以及phod基因丰度是影响植株根系P吸收量的主要因素。