Abstract

Arid and semiarid soils of southern Iran may fix a large content of applied potassium (K), but the fixed K may be gradually supplied to plants. Sixteen representative soils under orange cultivation (Citrus sinensis (L.) Osbeck) from arid and semiarid regions of southern Iran were selected and K fixation capacity of the soils were calculated. Then, the K-treated and control soil samples were extracted for K during 10 stages with 0.01 M CaCl₂. Results indicated that the studied soils were able to fix 25 to 280 mg K kg^–1. Mean contents of cumulative K released ranged 48–262 and 8–512 mg kg^–1 for the control and K-treated soils, respectively, with significant difference (p < 0.05). The control soils released 42–69% (mean of 57%) of K during the first three stages of extraction, and this was significantly (p < 0.05) lower than that for the K-treated soils (55–86% with mean of 69%). No significant difference was found between the control and K-treated soils in K release during 4 to 10 stages of extraction. The fixation of added K is occurred in more available sites (wedge zone) of clay minerals and the fixed K may be released easily during the K extraction experiment. Thus, the availability of the fixed K (originated from chemical fertilizers) is considerably more than the native non-exchangeable K ions due to its fixation in the mineral edges. Generally, calcareous soils in arid environments had a high proportion of K-bearing minerals and able to fix added K fertilizers, but the fixed K may be released easily during the plant growth season and it should be considered as a benefit process.

中文翻译：

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桔子栽培下部分石灰性土壤中钾的固定与释放

摘要

伊朗南部的干旱和半干旱土壤可能固定大量的施用钾（K），但固定的钾可能会逐渐提供给植物。从伊朗南部干旱和半干旱地区选择了16种代表性的橙色耕作土壤（Citrus sinensis（L.）Osbeck），并计算了土壤的K固定能力。然后，将K-处理的和对照的土壤样品中10个阶段用0.01M的CaCl提取对于K ₂。结果表明，所研究的土壤能够固结25至280 mg K kg ^–1。对照和经钾处理的土壤中累积释放的钾的平均含量分别为48–262和8–512 mg kg ^–1，差异显着（p<0.05）。在提取的前三个阶段，对照土壤释放出42-69％（平均57％）的钾，这显着（p<0.05）低于钾肥处理的土壤（55-86％，平均值为69％）。在提取的4到10个阶段中，对照土壤和K处理土壤的K释放量之间没有显着差异。添加的钾的固定发生在粘土矿物的更多可用位置（楔形区）中，固定的钾在钾提取实验中可能容易释放。因此，由于固定在矿物边缘，固定K（源自化肥）的可用性比天然不可交换的K离子高得多。通常，干旱环境中的钙质土壤中含钾矿物质的比例很高，并且能够固定添加的钾肥，但是固定的钾在植物生长季节可能容易释放，因此应视为有益过程。