Rapid assessment of soil compaction damage I. The SOILpak score, a semi-quantitative measure of soil structural form

Agricultural land evaluation is hampered by inadequate procedures for assessing the severity of soil compaction. Therefore, the ‘SOILpak scoring procedure’ has been developed within the Australian cotton industry to allow semi-quantitative assessment of soil structural form. It allows compaction severity in Vertisols to be separated into as many as 20 categories on a scale of 0.0 (severely compacted) to 2.0 (excellent structure for root growth). The procedure is based upon visual assessment of soil samples in the field as they are pulled apart by hand. The SOILpak scoring system is well accepted by advisory staff because of its speed and simplicity. However, there have been some problems with operator bias, and an inability to deal with continuity of vertical macropores, degree of encroachment of under-furrow compaction into the ridges where cotton is planted, and the presence of thin smeared layers. This paper presents a modified SOILpak scoring procedure that addresses these problems. Also, the SOILpak scoring procedure has been integrated with terminology in the ‘Australian Soil and Land Survey Field Handbooks’ so that it can be used by soil surveyors in other areas.