典型作物残茬磷分子形态表征

作物残茬还田对农业绿色发展和地力提升意义重大。我国作物残茬产量大，种类多，研究典型作物残茬中磷的赋存形态是预测其还田后作物有效性的前提。目前，液相磷-31核磁共振(³¹P-NMR)是可在分子水平上表征磷素形态的主流分析技术。而利用该技术表征作物残茬磷素形态的已有研究有限，且主要采用不同磷化合物的化学位移进行图谱解析。由于某些有机磷的峰位置相邻，其化学位移受样品pH等化学条件影响较大，导致单纯依靠文献报道进行图谱解析存在较大不确定性，并且识别出的有机磷种类偏少。该研究进行加标实验，选取典型作物残茬(玉米、小麦、水稻、大豆、花生、棉花),利用液相³¹P-NMR技术表征了不同部位(茎叶、谷壳和种子)磷的分子形态及其含量。研究发现，所有供试作物残茬中总磷含量均为种子>谷壳>茎叶。NaOH-EDTA前处理对供试作物残茬总磷有较高的提取率(73%～139%),平均105%。根据加标试验的³¹P-NMR图谱，供试样品中检测出的无机磷形态包括正磷酸盐、焦磷酸盐、三聚磷酸盐，有机磷包括植酸、α/β-甘油磷酸盐、单核苷酸，首次在...

Molecular Characterization of Phosphorus in Typical Crop Residues

The returning of crop residues to agricultural soils are of great significance to the development of Green Agriculture and soil fertility improvement. In China, there are various types of crop residues with high abundance. It is essential to characterize phosphorus (P) speciation in typical crop residues to predict the crop availability after returning them to the agricultural fields. To date, liquid-phase phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy is a state-of-the-art technique for characterizing P species at the molecular level. However, there were limited investigations on the characterization of P speciation in crop residuals by 31P-NMR spectroscopy. Moreover, spectral peaks of different P forms, generally assigned based on the published literature, were significantly affected by sample properties (i.e pH), which resulted in large uncertainty and limited P forms to be identified. Therefore, with spiking experiments, this study used 31P-NMR spectroscopy to characterize molecular P species in different parts (straw, chaff and seed) of the typical crops, including corn, wheat, rice, cotton, soybean and peanut. The results showed that the total P content in all investigated crop residues was seed > chaff > straw. NaOH-EDTA extractable P ranged from 73% to 139% of total P, with an average value of 105%. Based on the spiking experiments, inorganic P forms (orthophosphate, pyrophosphate, tripolyphosphate) and organic P forms (phytate, α and β-glycerophosphate, adenosine monophosphate) were detected in the investigated samples. Additionally, as one type of orthophosphate diesters, deoxyribonucleic acid was first detected in this study. In all investigated straw and chaff samples, the major P species were orthophosphates, comprising 49.3%~71.6% of the NaOH-EDTA extracted P, while P in the seeds was mainly phytate (48.5%~82.9%). With correction for diester degradation, orthophosphate diester (17.1%~33.5%) was more than orthophosphate monoester (9%~13.5%) in crop straw samples. In contrast, the orthophosphate monoester and orthophosphate diester percentages in chaff samples were 8.8%~23.2% and 8.8%~24.6% respectively, and orthophosphate monoester was the main component in seed samples (57.6%~82.9%). It showed that the investigated crop residues, especially straw, probably release orthophosphate and orthophosphate diesters as labile P forms for subsequent crop uptake after returning to the soil. These results provide a significant scientific basis for crop residue returning and P fertilization management in agricultural lands.