Physical and Chemical Properties of Soil Aggregates in a Brunizem Soil

Abstract

A surface sample of Sharpsburg silty clay loam was separated into aggregate fractions of diameters 4760 to 2380µ, 2380 to 1190µ, + … +, 37 to 18.5µ by means of rotary sieves and elutriators. A similar separation was made for primary particles. Each fraction of aggregates was analyzed for chemical and physical properties. The physical properties of aggregates were compared with those of primary particles. Data on water stability of aggregates show that as the diameter of aggregates decreased the stability increased. Particularly, aggregates of diameter 74 to 37µ and 37 to 18.5µ were different from the other fractions. Some of the differences in properties were: higher degree of aggregation, percentage of primary particles, available phosphorus, and exchangeable Ca++; lower moisture retention, percentage of organic matter, total nitrogen content, and exchangeable H+. At complete water saturation, aggregates and particles wetted under partial vacuum held greater amounts of water on a volume basis than did aggregates and particles wetted under atmospheric pressure. However, as tension was applied, more water was released from the aggregates and particles wetted under partial vacuum than under atmospheric pressure. At increased tensions, the differences between the two methods of wetting were less marked. At tensions of 0.33 atm. and higher, the moisture contents were nearly identical. Aggregates treated with VAMA soil additive, under both vacuum‐wetting and atmospheric‐wetting, released more water at successive tensions than did those without the additive.

Use of the Quantitatively Transformed Field Soil Structure Description of the US National Pedon Characterization Database to Improve Soil Pedotransfer Function

“…Their results are different than those in this study, but results in Rawls and Pachepsky (2002) comprised a subset of the data (weak grade and soft/dry Kay and Dexter (1990) also found that clay content increased as aggregate size increased. On the other hand, results in this study are different than in previous ones that reported a positive correlation between aggregate sizes and water retention (Tamboli et al 1964), and a negative correlation between aggregate size and bulk density (Wittmuss and Mazurak, 1958). However, the cited studies considered aggregates smaller than 2 cm, whereas in this study aggregates were as large as 10 cm.…”

The pore–solid fractal model of soil density scaling

“…The first set comes from the study of Chepil (1950) and provides aggregate densities for three soils of different texture over a range of aggregate sizes, and appears in Table 1. The second set provides aggregate densities for Sharpsburg soil (Wittmuss & Mazurak, 1958), and appears in Table 2.…”

Morphology, lacunarity and entropy of intra-aggregate pores: Aggregate size and soil management effects

“…Compaction from tillage together with rewetting and drying cycles homogenize the spatial distribution of mass within large size aggregates (Utomo and Dexter, 1981;Hadas, 1987;Lipiec and Hatano, 2003), and can alter the hierarchical arrangement of pores. Measurements on aggregate density have confirmed a decrease in total aggregate porosity with decreasing aggregate size (Wittmuss and Mazurak, 1958;Giménez et al, 2002). On the other hand, there are almost no direct observations of pore systems in soil aggregates.…”

“…Investigations of aggregate properties across sizes have been on water retention (Tamboli et al, 1964;Amemiya, 1965), aggregate stability/tensile strength (Wittmuss and Mazurak, 1958;Blanco-Canqui et al, 2005), organic matter content (Wittmuss and Mazurak, 1958;Rogowski and Kirkham, 1976;BlancoCanqui et al, 2005), particle size distribution (Tamboli et al, 1964;Rogowski and Kirkham, 1976) and chemical properties (Wittmuss and Mazurak, 1958;Kirchhof and Daniel, 2003). More recently, studies on carbon sequestration and soil microhabitats have renewed the interest on characterizing the property of soil aggregates (Beare et al, 1994;Blanco-Canqui and Lal, 2004).…”