中国农业科学

• 土壤肥料·节水灌溉·农业生态环境 • 上一篇    

腐植酸磷肥中的腐植酸对磷迁移的影响及机理

景建元,袁亮,张水勤,李燕婷,赵秉强   

  1. 中国农业科学院农业资源与农业区划研究所/农业农村部植物营养与肥料重点实验室,北京 100081
  • 收稿日期:2020-12-05 接受日期:2021-04-21 发布日期:2021-05-12

Effects and Mechanism of Humic Acid in Humic Acid Enhanced Phosphate Fertilizer on Fertilizer-Phosphorus Migration

JING JianYuan, YUAN Liang, ZHANG ShuiQin, LI YanTing, ZHAO BingQiang   

  1. Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture and Rural Affairs, Beijing 100081
  • Received:2020-12-05 Accepted:2021-04-21 Online:2021-05-12

摘要: 【目的】比较腐植酸增值磷肥中的腐植酸(PHA)与常规腐植酸(HA)对肥料磷迁移、Ca2+及磷酸盐吸附特征的差异,明晰腐植酸在磷肥增效过程中的作用。【方法】实验室分别制备腐植酸、腐植酸磷肥及普通磷肥,利用腐植酸“碱溶酸析”的原理,通过调节腐植酸磷肥溶液pH分离得到PHA。研究土壤表层磷肥配施两种添加量HA或PHA对肥料磷迁移状况的影响,HA或PHA的配施量分别为施磷量的0.5%与5%,代号分别为0.5HA+P、0.5PHA+P、5HA+P及5PHA+P,同时设置单施磷肥(P)及不施肥(CK)两个处理。并通过HA或PHA对Ca2+及磷酸盐的吸附特征解释二者对肥料磷迁移存在差异的原因。【结果】HA或PHA配施磷肥,肥料磷的迁移距离与迁移量均高于P处理:P处理肥料磷可以迁移到距施肥层垂直距离42 mm处,而配施HA或PHA处理可以分别到达距施肥层46 mm与50 mm处,这与HA或PHA对土壤Ca2+存在较高的吸附容量,进而减少土壤对磷的固定有关。距施肥层42 mm以后,土壤速效磷总量占总施磷量的累积百分数基本趋于不变,且0.5 HA+P ≈ 5PHA+P > 5HA+P > 0.5PHA+P > P处理。PHA对肥料磷迁移的促进作用会随其添加量的提高而增强,而提高HA用量反而会减弱其对肥料磷迁移的促进作用,这与PHA移动性强于HA,对磷酸盐的吸附弱于HA有关。HA与PHA对Ca2+的吸附均是膜扩散与颗粒内扩散综合作用的结果,但是与HA相比,Ca2+向PHA颗粒表面扩散的难度降低,在PHA颗粒内部扩散的难度变大。Langmuir等温吸附模型可以很好地拟合HA或PHA对Ca2+的等温吸附曲线,且HA对Ca2+理论最大吸附量高于PHA,然而PHA对Ca2+的吸附以化学吸附为主。【结论】腐植酸磷肥中的腐植酸与普通腐植酸均对Ca2+存在一定的吸附能力,因此均可以促进肥料磷的迁移,但是磷肥配施腐植酸磷肥中的腐植酸,肥料磷的迁移距离大于常规腐植酸,这可能是腐植酸磷肥中腐植酸增效磷肥的一个原因。

关键词: 腐植酸磷肥, 腐植酸, 肥料磷迁移, 钙离子, 吸附

Abstract: 【Objective】The difference between HA (raw humic acid) and PHA (humic acid which extracted from humic acid enhanced phosphate fertilizers (HAP)) on fertilizer-phosphorus migration, Ca2+ and phosphate adsorption characteristics was systematacially compared to provide the theoretical basis for the study on high-efficiency mechanism of humic acid enhanced phosphate fertilizer.【Method】In this study, HA, HAP, and conventional phosphate fertilizer were prepared in the laboratory, and PHA was extracted by adjusting the pH of HAP’s solution based on the method of alkali-extraction acid-precipitation. Effects of HA and PHA applicated with phosphate fertilizer on the migration of fertilizer-phosphorus in soil was investigated. The addition of HA or PHA accounted for 0.5% and 5% of the application amount of phosphate fertilizer, and marked with 0.5HA+P, 0.5PHA+P, 5HA+P, and 5PHA+P, respectively. Only phosphate fertilizer application (P) and no fertilizer application (CK) were arranged at the same time. In addition, the adsorption characteristics of HA or PHA on Ca2+ and phosphate were studied to reveal the mechanism that HA and PHA showed different performance on phosphorus migration. 【Result】Both HA and PHA could promote the migration of fertilizer-phosphorus. Phosphorus could migrate to 42 mm vertical distance from the fertilizer layer under the treatment of P, while it could reach 46 mm and 50 mm away from the fertilizer layer, respectively, when phosphate fertilizers application combined with HA and PHA. This result resulted from the fact that HA or PHA had a higher adsorption capacity on soil Ca2+, and the application of HA or PHA reduced phosphorus fixation. The cumulative percentage of soil available P in total P application tended to be stable after 42 mm away from the fertilizer layer, and 0.5 HA+P ≈ 5PHA+P > 5HA+P > 0.5PHA + P > P. The promotion effect of PHA on fertilizer-phosphorus migration would be enhanced with the addition of PHA increase, while HA was the opposite. Which might be related to the stronger mobility and the weaker phosphate adsorption of PHA than that of HA. The adsorption of Ca2+ by HA and PHA was the result of membrane diffusion and intra-particle diffusion. However, the difficulty of Ca2+ diffusion to the surface of PHA particles was lower than that of HA, and the difficulty of Ca2+ diffusion in the interior of PHA particles was higher than that of HA. Langmuir isothermal adsorption model could well fit the isothermal adsorption curves of HA or PHA on Ca2+, and the theoretical maximum adsorption capacity of HA on Ca2+ was higher than that of PHA, but the adsorption of PHA on Ca2+ was mainly chemical adsorption.【Conclusion】Both raw humic acid (HA) and humic acid extracted from humic acid enhanced phosphate fertilizers (PHA) have certain ability to adsorb Ca2+, so they can promote the migration of fertilizer-phosphorus in the soil. However, the migration distance of fertilizer-phosphorus of PHA was longer than that of HA, when phosphate application was combined with HA or PHA. This may be one reason why PHA can improve the use efficiency of phosphate fertilizer.

Key words: humic acid enhanced phosphate fertilizer, humic acid, fertilizer-phosphorus migration, calcium ion, adsorption