ABSTRACT

Top soil burning may occur in shifting cultivation in hills, forest fire or burning of agricultural straw. It may affect the mechanisms of potassium (K) release by different extractants. Cumulative K release from six calcareous soils before and after heating (at 350°C) during 10 times extraction with 0.025 M CaCl₂, HCl, oxalic and citric acids was determined. Initial K release was increased from 8–23 mg kg⁻¹ to 13–47 mg kg⁻¹ by heating the soils. Citric acid extracted more K than other solutions in the initial stage of K release. Cumulative K release ranged from 61 mg kg⁻¹ for Torriorthents (containing high calcium carbonate and low clay) to 248 mg kg⁻¹ for Haploxererts (containing low calcium carbonate and high illitic clay). Citric and oxalic acids extracted more K than CaCl₂ and HCl. Heated soils released more K than unheated soils to the different extractants (62, 86, 112 and 105% increase for CaCl₂, HCl, oxalic and citric acids, respectively). It is concluded that presence of calcium carbonate in soil affects the mechanisms of K release; in highly calcareous soils, exchange reactions were the main mechanism, while in slightly calcareous soils, exchange reactions and mineral dissolution were involved in the K release.

摘要

山地轮耕、森林火灾或焚烧农作物秸秆等都可能发生表土烧毁。它可能会影响不同萃取剂释放钾 (K) 的机制。_{测定了用 0.025 M CaCl 2}、HCl、草酸和柠檬酸提取 10 次期间六种石灰质土壤在加热（350°C）前后的累积钾释放量。通过加热土壤，初始钾释放量从 8–23 mg kg ^-1增加到 13–47 mg kg ^{-1 。}在钾释放的初始阶段，柠檬酸比其他溶液提取更多的钾。累积的 K 释放范围从Torriorthents（含有高碳酸钙和低粘土）的61 mg kg ^{-1到 248 mg kg -1}用于 Haploxererts（含有低碳酸钙和高伊利石粘土）。柠檬酸和草酸比 CaCl ₂和 HCl提取更多的 K。加热的土壤比未加热的土壤向不同萃取剂释放更多的钾（CaCl ₂、HCl、草酸和柠檬酸分别增加 62%、86%、112% 和 105%）。结论是土壤中碳酸钙的存在会影响钾的释放机制；在高钙质土壤中，交换反应是主要机制，而在轻钙质土壤中，交换反应和矿物溶解参与了钾的释放。