A comparison of methods for measuring water-stable aggregates: implications for determining environmental effects on soil structure

doi:10.1016/0016-7061(93)90102-Q

Geoderma

Volume 56, Issues 1–4, 15 March 1993, Pages 87-104

https://doi.org/10.1016/0016-7061(93)90102-Q Get rights and content

Abstract

This paper describes the effects of different pretreatment conditions and wet-sieving procedures on water-stable aggregate distributions of sandy and clayey textured soils (Cecil, Pacolet, and Hiwassee Series) from the Piedmont of the southern Appalachian mountains of Georgia, USA. Four soil pretreatment procedures were compared: (1) air-dried, capillary wetted (AD-CW), (2) air-dried, tension wetted (AD-TW), (3) air-dried, slaked (AD-SL), and (4) field-moist, capillary wetted (FM-CW). Air-drying soils resulted in a greater quantity of aggregates in the coarser fractions (> 250 μm), as compared to field-moist soils, with a consequent reduction in the finer fractions (> 250 μm). Differences between methods of wetting air-dried soils were more pronounced for the clayey soils where both AD-CW and AD-SL resulted in a greater proportion (22–24%) of the soil mass in the finer fractions (> 250 μm), as compared with AD-TW (4.5%). The FM-CW procedure had the lowest coefficients of variation (2–8%) for repeated measurements.

The AD-CW and FM-CW procedures were also used to compare the effects of cropping systems [conventional tillage (CT) (soybean/fallow), CT (sorghum/fallow), and no-tillage (NT) (sorghum/clover)], erosion classes (slight, moderate, and severe) and irrigation (drip-irrigated or nonirrigated) on water-stable aggregates (> 250 μm). In general, water-stable aggregates increased with decreasing intensity of cultivation, increasing severity of erosion and irrigation. Air-drying soils resulted in less differences in water-stable aggregates between treatments, but provided more detailed information on the interactive effects of cropping system and irrigation as compared with the field-moist condition. Similar differences were observed in aggregate disruption rates that were calculated from the aggregates recovered after wet-sieving for intervals of 1–32 min. Although water-stable aggregates were lower by FM-CW, this procedure showed greater separation of treatment means (e.g. erosion classes) than the AD-CW procedure.

We also compared single versus multiple-sieve techniques for describing the effects of pretreatment conditions on aggregate distributions. For the clayey Pacolet soil, a fine fractionation into eleven aggregate size classes revealed the greatest differences (P > 0.05) between the FM-CW and AD-CW procedures, while a coarse fractionation into macro- (> 250 μm) and micro- (> 250 μm) aggregates showed no differences. However, for the sandy Hiwassee soil differences in aggregate distributions between the FM-CW and AD-CW procedures were found at most levels of fractionation, but were not detected by comparing the calculated mean weighted diameters. In general, our findings emphasize the value of comparing soil specific responses to different pretreatment conditions, particularly those that compare the distributions of aggregates among size classes, as a means for describing environmental influences on soil structure.

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Contributed paperA comparison of methods for measuring water-stable aggregates: implications for determining environmental effects on soil structure

Abstract

Soil Biol. Biochem.

Adv. Agron.

Modification of soil characteristics of degraded soil surfaces by biomass input and tillage affecting soil water regime

Soil cohesion as affected by freezing, water content, time and tillage

Soil Sci. Soc. Am. J.

Comparison of four prewetting techniques in wet aggregate stability determination

Can. J. Soil Sci.

Microaggregates in soil

J. Soil Sci.

Aggregate structure and carbon, nitrogen and phosphorus in native and cultivated soils

Soil Sci. Soc. Am. J.

Particle-size analysis

Aggregate stability of an eroded and desurfaced Typic Argiustoll

Soil Sci. Soc. Am. J.

Generation of microcracks in moulded soils by rapid wetting

Aust. J. Soil Res.

Carbon mineralization in soil size fractions after various amounts of aggregate disruption

J. Soil Sci.

Aggregate stability of soils from Western United States and Canada

Soil cohesion as affected by time and water content

Soil Sci. Soc. Am. J.

Aggregate stability and size distribution

Contributed paper
A comparison of methods for measuring water-stable aggregates: implications for determining environmental effects on soil structure