Changes in dispersible clay content, organic carbon content, and electrolyte composition following incubation of sodic soil
Changes in dispersible clay content, organic carbon content, and electrolyte composition following incubation of sodic soil
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DOI：
10.1071/s98024
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发表时间：
1998
期刊：
影响因子：
1.6
通讯作者：
P. N. Nelson;J. Baldock;J. Oades
中科院分区：
文献类型：
--
作者：
P. N. Nelson;J. Baldock;J. Oades
可分散粘土的测定对土体结构稳定性问题的诊断具有重要意义。然而，粘土的分散性随着含水量和时间的变化而变化。本研究的目的是确定在不同含水量下的碱土培养如何影响粘土的分散性。从维多利亚州Kyabram的实验牧场收集了两种表层土壤（深度0- 0.1 m），一种是钠盐[交换性钠含量（ESP） 9.7]，另一种是非钠盐（ESP 3.8）；从南澳大利亚州Two Wells的农田收集了两种土壤，一种是钠盐表层土壤（深度0- 0.1 m, ESP 6.9）和相应的底土（深度0.2 -0 m, ESP 25.7）。采用分块设计培养264天。主要处理是土壤类型和培养含水量：连续风干、连续湿（-50 kPa）或湿/干循环。次处理为分析时的含水量：空气干或湿（-50 kPa）。在湿土上测定的粘土分散比在干土上测定的要大，而不管先前孵育期间的含水量如何。随着土壤湿润时间的延长，电导率增加，钠吸附比（SAR）、pH和有机碳含量降低。在湿润的Kyabram土壤中，易分散的粘土含量随着SAR的增加而增加。湿润/干燥状态下中等分散性粘土含量的减少与电解质成分无关，而归因于颗粒重排和胶结。尽管碳水化合物和脂肪类物质的净损失，但粘土的分散性随时间的推移而下降。这项工作的一个含义是，土壤有机质的分解，即使在没有新鲜添加物的情况下，也可能通过改变电解质的浓度和组成来减少粘土在碱土中的分散。
Measurement of dispersible clay is important for the diagnosis of structural stability problems in soil. However, clay dispersibility is known to change with water content and time. The purpose of the present study was to determine how incubation of sodic soil under different water content regimes influences clay dispersibility. Two topsoils (depth 0-0·1 m), one sodic [exchangeable sodium percentage (ESP) 9 · 7] and the other non-sodic (ESP 3·8), were collected from an experimental pasture at Kyabram, Victoria, and 2 soils, a sodic topsoil (depth 0-0·1 m, ESP 6·9) and the corresponding subsoil (depth 0·2-0 m, ESP 25·7), were collected from a cropped field at Two Wells, South Australia. The soils were incubated for 264 days in a split-plot design. The main treatments were soil type and incubation water content: continuously air-dry, continuously wet (-50 kPa), or with wet/dry cycles. The subtreatment was water content at analysis: air dry or wet (-50 kPa). Clay dispersion was greater when measured on wet soils than dry soils, irrespective of water contents during the prior incubation. Electrical conductivity increased, and sodium adsorption ratio (SAR), pH, and organic carbon content decreased as a function of the time for which the soils were wet. In the Kyabram soils that were wet when analysed, easily dispersible clay content increased with SAR. Decreases in moderately dispersible clay under the wetting/drying regime were not related to electrolyte composition, and were attributed to particle rearrangement and cementation. The decreases in clay dispersibility with time occurred despite net losses of carbohydrate and aliphatic materials. An implication of the work is that the decomposition of soil organic matter, even in the absence of fresh additions, may reduce clay dispersion in sodic soils by altering electrolyte concentration and composition.