Addition of Fe-humic acids to overcome analytical issues in measurements of isotopically exchangeable P in soil

IF 4 2区 农林科学 Q2 SOIL SCIENCE
Fien Degryse, William Tucker, Michael J. McLaughlin
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引用次数: 0

Abstract

Isotopic dilution has been widely used to measure isotopically exchangeable phosphorus (P) in soil (E value), as a measure of potentially plant-available P. However, in soils with low E values and/or strong P sorption, measurement of E values can be challenging due to very low solution concentrations and the interference of colloidal non-exchangeable species, thus confounding the measurements in the soils of most interest. The addition of a complexing compound could increase solution concentrations and reduce these analytical issues, as has been found in the case of metals. Therefore, we investigated the addition of Fe-humic acid (Fe-HA) as a P-complexing compound to the soil suspension prior to isotopic exchange. This results in the formation of P-Fe-HA complexes, thus increasing P solution concentrations by solubilizing P from the labile pool and reducing errors caused by suspended colloids. We used this method to measure E values in five soils with low P status, without or with the addition of carrier P. The addition of Fe-HA (at 50 or 200 mg Fe-HA/L to the equilibration solution) substantially decreased the measured E value without carrier P addition in four of the five soils, while there was no or little effect when carrier P was added. The higher Fe-HA rate increased solution concentrations of stable and radioactive P more than the lower rate, but there was no significant difference in measured E values between the two Fe-HA rates. The method was also applied to 15 subsoils with low P status. Overall, our results indicated that the addition of Fe-HA provides an easy and robust way to avoid analytical issues in the determination of E values in soils with low concentrations of P in solution.

添加铁-腐植酸以克服土壤中同位素交换性 P 测量中的分析问题
然而,在 E 值较低和/或 P 吸附性较强的土壤中,由于溶液浓度非常低以及胶体非交换性物种的干扰,E 值的测量可能具有挑战性,从而混淆了最感兴趣的土壤中的测量结果。添加络合剂化合物可以提高溶液浓度,减少这些分析问题,这一点在金属的研究中也有发现。因此,我们研究了在同位素交换之前向土壤悬浮液中添加铁-腐植酸(Fe-HA)作为钾络合化合物的方法。这将形成 P-Fe-HA 复合物,从而通过溶解易溶池中的 P 来增加溶液中的 P 浓度,并减少悬浮胶体造成的误差。在不添加载体 P 或添加载体 P 的情况下,在五种土壤中的四种土壤中添加 Fe-HA(在平衡溶液中添加 50 或 200 毫克 Fe-HA/升)会大大降低所测得的 E 值,而添加载体 P 则没有影响或影响很小。较高的 Fe-HA 加量比较低的 Fe-HA 加量更能增加溶液中稳定态 P 和放射性 P 的浓度,但两种 Fe-HA 加量之间的 E 值测量值没有显著差异。该方法还应用于 15 个低 P 状态的底土。总之,我们的研究结果表明,在测定溶液中 P 浓度较低的土壤中的 E 值时,添加 Fe-HA 是避免分析问题的简便而可靠的方法。
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来源期刊
European Journal of Soil Science
European Journal of Soil Science 农林科学-土壤科学
CiteScore
8.20
自引率
4.80%
发文量
117
审稿时长
5 months
期刊介绍: The EJSS is an international journal that publishes outstanding papers in soil science that advance the theoretical and mechanistic understanding of physical, chemical and biological processes and their interactions in soils acting from molecular to continental scales in natural and managed environments.
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