Search

Clay delving in strongly texture-contrast soils brings up subsoil clay in clumps ranging from large clods to tiny aggregates depending on the equipment used and the extent of secondary cultivation. Clay delving usually increases crop yields but not universally; this has generated questions about best management practices. It was postulated that the size distribution of the subsoil clumps created by delving might influence soil-water availability (and hence crop yield) because, although the clay increases water retention in the root-zone, it can also cause poor soil aeration, high soil strength and greatly reduced hydraulic conductivity. We prepared laboratory mixtures of sand and clay-rich subsoil in amounts considered practical (10% and 20% by weight) and excessive (40% and 60% by weight) with different subsoil clod sizes ( Additional keywords: aggregate size distribution, soil physical limitation, sandy soils, tillage. Received 22 April 2015, accepted 18 July 2015, published online 11 April 2016, Introduction Texture-contrast soils (Isbell 2002) dominate a significant proportion of the cropping lands in the Mediterranean parts of southern Australian and present a peculiar set of soil physical and chemical [...]

Abstract: Defining soil clay minerals as all inorganic particles < 2 µm would enhance their predictive power for soil functions. The future task is to unravel the prominent functional role of clay associations in the “ultimate particles” in soils–microaggregates. High energy techniques and decomposition of XRD patterns offer the prospect of understanding associations of silicates, oxides and organic matter within microaggregates. [ABSTRACT FROM AUTHOR]