Promoting Effect of Natural Humic Material on the Release of Water-soluble Phosphorus from Low-grade Phosphate Rock Powder
[Objective]The objective of this study was to disclose the structural characteristics and the relationship with phosphorus validity in the promoted phosphate rocks(PPR),which were made by mixing low-grade phosphate rock powder and natural humic material materials.[Method]Continuous water extraction,X-ray diffraction(XRD),fourier transform infrared spectrometry(FTIR),and pot experiment were carried out to explore the phosphorus validity mechanism of PPR from dynamic release,structural characteristics and fertilizer effects.[Result]The results showed that the release of water-soluble phosphorus showed an increasing trend with the increase of activator addition.After five leachings,the total water-soluble phosphorus released was 1.54 and 1.72 times higher than that of the control treatment when the mass ratio of natural humic material or HNO3-treated natural humic material mixed with low-grade phosphate rock powder was 20∶80.X-ray diffraction analysis showed that the characteristic diffraction peaks corresponding to P2O5 and Ca(PO3)2 showed a significant decrease after five leaching of natural humic material or HNO3-treated natural humic material mixed with low-grade phosphate rock powder.The results of FTIR spectral analysis showed that the disappearance of the PO43-symmetric stretching vibration v1 at 966 cm-1 was evident after five leaching cycles of natural humic material or HNO3-treated natural humic material mixed with low-grade phosphate rock powder,while the intensity of the PO43-asymmetric stretching vibration v3,H2PO4-associated absorption peaks,and HPO42-associated absorption peaks at 1 127,673 and 612 cm-1 were significantly decreased.The pot experiment further showed that natural humic material or HNO3-treated natural humic material as a high-quality organic material applied at 6 g·kg-1 or 9 g·kg-1 while mixed with low-grade phosphate powder at a 20∶80 mass ratio could significantly increase the available phosphorus content of the soil,while rapidly increasing the soil organic matter content.When natural humic material was applied at 9 g·kg-1 and mixed with low-grade phosphate powder at a mass ratio of 20∶80,soil available phosphorus was increased by 29.86％,29.47％,and 36.48％while soil organic matter was increased by 34.16％,8.05％,and 47.40％,respectively,compared to control treatment on days 14,30,and 60 after sowing.Also,when HNO3-treated natural humic material was applied under similar conditions,soil available phosphorus was increased by 36.97％,94.44％,and 34.51％while soil organic matter was increased by 27.29％,14.57％,and 45.41％,respectively,compared with control treatment on days 14,30,and 60 after sowing.[Conclusion]Natural humic material or HNO3-treated natural humic material with acidic pH,high specific surface area,high humus content and a high number of active functional groups were responsible for enhancing the water-soluble phosphorus content of low-grade phosphate rock powder and soil available phosphorus.
万方数据
维普
