土壤-作物系统中有机结合态磷肥的高效机理研究

Developing new phosphorus (P) fertilizers with enhanced property and function is a fundamental way to solve the current bottleneck problems within the agronomy and soil-environmental science. Organically-bonded P fertilizers with low sorption capacity show high activity and mobility in soils after application, and thus become popular in the field of enhanced P fertilizer development. Clarifying the fate and turnover of organically-bonded P fertilizers in soils after application is critical to improve fertilizer efficiency, decrease soil P accumulation, and control agricultural non-point pollution. However, research in this field is not well-documented until now. In this program based on pot experiment, we intend to measure the distribution of organically-bounded P fertilizers between the soil labile/non-labile P fractions, growing crops and microbial P pools as well as its spatial-temporal features by P-33 isotope tracer technique. Cutting-edge spectroscopes at the molecular level, including P-31 NMR, bulk/μ-XANES, μ-XRF, are combined to probe P speciation of organically-bonded P fertilizer, as well as the P turnover and transformation after its application. Results will reveal the deep mechanisms of the enhanced efficiency for the organically-bonded P fertilizers, which provide forward-looking basis for sustainable development of agriculture, optimized management of agricultural soil P, and controlled agricultural non-point source discharge.

新型高效磷肥的研发是从根本上解决当前农学与土壤环境学发展瓶颈的新思路。有机结合态磷肥施入土壤后抗固定性能强，反应活性高，是当今磷肥改性增效技术发展的主流方向。阐明有机结合态磷肥输入土壤后的归趋特征及赋存形态转化，对提高磷肥利用率、降低农田磷素富集及农业面源污染至关重要。但目前该方面的研究尚不多见。本项目拟基于室内模拟盆栽试验，利用磷-33同位素示踪技术追踪有机结合态磷肥在土壤不同活性磷库-微生物-作物系统中量化归趋的时空特征，结合液相磷-31核磁共振、同步辐射X射线吸收近边结构谱（bulk/μ-XANES）、微区X射线荧光光谱（μ-XRF）等前沿技术从分子水平上表征有机肥料磷初始形态及施入土壤后赋存形态的转化特征，揭示有机结合态磷肥高效性的深层机制，为农业可持续发展、农田土壤磷素优化管理、农业面源污染减排提供前瞻性理论依据。

当前，化学磷肥不合理施用引发的资源危机和环境问题日益凸显，鉴于有机结合态磷肥不易被土壤组分固定，在土壤中移动性强，潜在作物有效性高，研制新型磷肥、提高磷肥利用率是保障农业生产、环境安全及可持续集约化的关键。阐明新型磷肥输入土壤后的归趋特征及赋存形态转化对理解其高效机制至关重要。本项目基于土壤室内培养与小麦盆栽试验，实验设置不施磷肥、无机磷肥（磷酸二氢钠）、淀粉基磷肥、淀粉与磷酸二氢钠简单混合四个处理，各处理总磷添加等量设置，分析不同时段外源添加不同磷肥在土壤活性/非活性磷库、微生物、植物间周转归趋及量化分配的动态特征，结果表明施用无机磷肥短时间内大幅提高活性组分NaHCO3提取态磷（Ca2-P）含量，其半衰期较短，同时可较快的向较稳态磷组分转化，其后续作物有效性可能较低；无机磷与淀粉配施，一定程度上更易加速以上过程；而施用淀粉基磷肥后，其添加磷可贡献到多种磷组分上，活性磷组分向较稳态磷组分的转化速率更低，推测其具有一定的缓释作用，可在较长时间内供给作物生长，同时，活性组分Ca2-P含量的增加较无机磷肥处理更少，并表现出更长的半衰期，可以推测其施用后短期内可能的环境风险较低。应用同步辐射X射线吸收近边结构谱、液相磷-31核磁共振等现代分析技术从分子水平上表征有机磷肥本身形态及施用于土壤后赋存形态的转化特征，发现了第八周淀粉基磷肥处理土样中铁磷含量高于其他处理土样的直接证据，印证了之前的磷组分分析结果，同时，针对有机磷形态转化特征的研究显示相比于无机磷肥处理，淀粉基磷肥施用表现出更强的正磷酸二酯对作物的供给作用。本研究通过探讨新型磷肥施用后在土壤中的形态转化，有助于深入理解有机结合态磷肥的高效机制，为新型高效磷肥的改性增效提供前瞻式理论依据。