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首页> 外文期刊>Soil Research >Genesis of cohesive soil horizons from north-east Brazil: role of argilluviation and sorting of sand
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Genesis of cohesive soil horizons from north-east Brazil: role of argilluviation and sorting of sand

机译：巴西东北部粘性土壤层的成因：沙化作用和沙粒分选的作用

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Cohesive horizons are widespread along the Brazilian coastal tablelands and, despite their importance to soil management under intensive cultivation, their genesis remains, in many aspects, controversial. Studies diverge and indicate the participation of different mechanisms in the formation of these soil horizons. Although clay illuviation has been considered as one of the processes determining the formation of this soil attribute, recent studies suggest a limited participation of this soil process. The aim of the present study was to evaluate the relative contribution of argilluviation and sorting of sand to the genesis of cohesive horizons in an Ultisol toposequence from a toposequence from north-east Brazil. Soil samples were collected from cohesive and non-cohesive horizons from four soil profiles. We determined bulk soil density (BD), penetration resistance (PR), particle size distribution and the percentage of different sand fractions. The sand fractionation data were treated statistically to obtain different grain size parameters, such as mean grain size, sorting and kurtosis. An additional micromorphological study was performed on cohesive and non-cohesive horizons. The lowest BD and PR were recorded in non-cohesive horizons (1.53Mgm(-3) and 0.74MPa, respectively), whereas significantly higher values of BD (1.66-1.80Mgm(-3)) and PR (2.61-7.71MPa) were observed in cohesive horizons. Thin sections of cohesive soil horizons showed a significant reduction in void sizes and interconnecting pores compared with non-cohesive soil horizons. The higher values of BD and PR observed in the cohesive horizons are apparently related to this poorly interconnected void network. Textural pedofeatures observable with optical microscopy, which indicate argilluviation, were only found in one cohesive horizon. Sand fractionation showed a predominance of medium and fine sand fractions and indicated the dominance of poorly selected sand in cohesive horizons, probably causing the higher BD and PR values. However, the presence of textural pedofeatures (clay coatings) in one of the cohesive horizons studied may indicate a combined contribution of sand heterogeneity and argilluviation in the genesis of these horizons. Overall, the results of the present study showed that subtle variations in the distribution of basic soil components (i.e. particle size fractions) may determine the formation of cohesive horizons and thus must be taken into account in future studies aiming to predict their spatial distribution and to establish more efficient management strategies.
机译：粘性地带分布在巴西沿海平原上，尽管它们在集约耕作下对土壤管理具有重要意义，但其成因在许多方面仍存在争议。研究存在分歧，并表明不同机制参与了这些土壤层的形成。尽管黏土照射被认为是决定这种土壤属性形成的过程之一，但最近的研究表明这种土壤过程的参与有限。本研究的目的是评估从巴西东北部到北部的Ultisol北部到北部的Ultisol北部到南部的凝聚作用和沙粒分类对粘性层位成因的相对贡献。从四个土壤剖面的粘性和非粘性层收集土壤样品。我们确定了散装土壤密度（BD），抗渗透性（PR），粒度分布以及不同砂级分的百分比。对砂分馏数据进行统计处理以获得不同的粒度参数，例如平均粒度，分选和峰度。在内聚和非内聚水平上进行了另外的微形态学研究。 BD和PR最低记录是在非粘性层中（分别为1.53Mgm（-3）和0.74MPa），而BD（1.66-1.80Mgm（-3））和PR（2.61-7.71MPa）明显更高在凝聚的视野中被观察到。与非粘性土层相比，粘性土层的薄部分显示出孔隙大小和相互连通的孔隙显着减少。在凝聚层中观察到的较高的BD和PR值显然与该不良互连的空隙网络有关。光学显微镜可观察到的纹理性状特征，表明藻状体化，仅在一个凝聚的视野中发现。砂分馏显示出中等和精细的砂分占优势，表明在粘性层中选择不佳的砂占优势，可能导致较高的BD和PR值。但是，在研究的一种粘性地层中存在纹理特征（粘土涂层）可能表明，这些地层的成因是砂的非均质性和泥沙化作用的共同贡献。总体而言，本研究的结果表明，基本土壤成分（即粒径分数）分布的细微变化可能决定了凝聚层的形成，因此在未来的研究中必须考虑这些因素，以预测其空间分布并建立更有效的管理策略。

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