ABSTRACT

The main Brazilian soil testing laboratories use Mehlich-1 solution for the determination of available potassium in the soil. However, this procedure has chemical and operational limitations. In search of alternatives for Mehlich-1, this study was to compare different extraction solutions, vis: Mehlich-1 and 3, and 1.0 mol L⁻¹ ammonium chloride (NH₄Cl) and 1.0 mol L⁻¹ ammonium acetate (NH₄OAc), as soil-K index to predict K availability to corn plants in southern Brazilian soils. The greenhouse pot experiment consisted of 30 soils grown with 2 corn crops. All soil-K index presented high correlation and determination coefficients between K uptake by corn plants and the K extracted from the soil. The Mehlich-1 solution was consistently better correlated with K uptake by corn plants than NH₄OAc and NH₄Cl but extracted less exchangeable K of the soils. Grouping soils with similar mineralogy and physicochemical properties enhances and improves the prediction of K availability for corn plants. Moreover, the K saturation index can be used as a sole indicator of K availability to plants. Overall, the results indicate that it is feasible to replace the traditional solution Mehlich-1 in the extraction of soil exchangeable K by solution of NH₄Cl mol L⁻¹ in laboratories that have an Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).

摘要

巴西主要的土壤测试实验室使用 Mehlich-1 溶液来测定土壤中的有效钾。然而，该程序具有化学和操作限制。在寻找 Mehlich-1 的替代品时，本研究比较了不同的萃取溶液：Mehlich-1 和 3，以及 1.0 mol L ^-1氯化铵 (NH ₄ Cl) 和 1.0 mol L ^-1乙酸铵 (NH ₄OAc)，作为土壤钾素指数，用于预测巴西南部土壤中玉米植物的钾素可用性。温室盆栽试验包括 30 块土壤，种植 2 种玉米作物。所有土壤钾素指数在玉米植株吸收钾素与从土壤中提取的钾素之间都表现出高度相关性和决定系数。与 NH ₄ OAc 和 NH ₄相比，Mehlich-1 溶液始终与玉米植物吸收钾的相关性更好Cl 但提取的土壤交换性 K 较少。将具有相似矿物学和物理化学特性的土壤分组可增强和改进对玉米植物钾含量的预测。此外，钾饱和指数可用作植物对钾可用性的唯一指标。总体而言，结果表明，在具有电感耦合等离子体发射光谱法 (ICP-OES) 的实验室中，用 NH ₄ Cl mol L ^-1溶液代替传统溶液 Mehlich-1 提取土壤可交换钾是可行的.