The Double Spade Method: a ‘mini-profile’ visual soil evaluation technique

Abstract

Visual Soil Evaluation (VSE) methods are established for soil quality assessment and focus on the examination of soil structure and associated anthropogenic impacts. VSE techniques, of which numerous types exist, are successfully used internationally both in soil research and as sustainable soil management tools. Techniques are generally categorised into profile and spade methods. Profile methods examine entire soil profiles in soil-pits to depths of ~ 1.5 m, exploring interactions between inherent soil features and anthropic management at specific sample points. Spade methods examine the upper soil profile, often by extracting sample blocks of topsoil by spade and focus on anthropic impacts. The VESS method (Guimarães et al., 2011) is a widely used spade method and involves assessment of soil sample blocks to 25 cm depth. However, in arable soils, important structural features may occur just below this depth such as plough pans, which VESS may not capture. The SubVESS method (Ball et al., 2015) follows principles of VESS but allows assessment to ~ 1 m depth. However, the later involves soil-pit excavation by mechanical means, which may be destructive, costly, time consuming and limit replication. When used in on-farm situations by farmers or advisors, full soil-pit excavation may not be desirable. Here we describe a method previously outlined (Emmet-Booth et al. 2018) called the Double Spade Method (DS) designed to examine miniprofiles in soil pits to 40 cm depth, therefore capturing potential structural features below the VESS assessment depth, without requiring full soil-pit excavation.