Mar 10, 2017

Agronomy & physiology WCRC Agro-physio-australia WCRC1
Abstract                                                                         Back to Table of contents

Techniques for assessing the severity of soil compaction were evaluated, mostly under commercial conditions, at twelve sites with contrasting degrees of damage.  The soils at each site are Vertisols used to produce irrigated cotton.  The reference technique for soil structural assessment was clod shrinkage analysis.  This procedure is prone to sampling bias, but until recently it was widely regarded to be the best available method.  We combined a number of the shrinkage parameters to provide a soil structural index (SSI).  A broad range of mostly cheaper soil structural and plant measurements were regressed against the SSI.  There was no single technique that accounted for more than 49% of the variation in the SSI.  Groups of alternative structural form measurements accounted for substantially more of the variation, but their routine use by cotton managers was considered to be impractical.  There was a lack of correlation between cotton lint yield and SSI when all the data were considered together.  Sites with poor soil structure frequently had high yielding crops, due to high nitrogen application rates and frequent irrigations, which appear largely to have compensated for the adverse effects of soil compaction on crop growth and yield.  However, such an approach to farming is inefficient, and may lead to off-site pollution, so the search for adequate procedures to measure the degree of compaction must continue.  Associated research carried out since our study was undertaken has demonstrated the potential of image analysis procedures, and of an improved version of the SOILpak scoring system.

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