The ‘Invisible’ Subsoil: An Exploratory View of Societal Acceptance of Subsoil Management in Germany

Abstract

Subsoil, commonly defined as horizons below the working depth of 30 cm, has traditionally received little explicit attention in policy discussions on soils. Recently, however, there has been growing recognition among scientists of the issues of subsoil (re-)compaction and of the role of subsoil as a resource that can offer valuable nutrients and water for plants. Subsoil management could provide an option to sustainably maintain yields in the context of climate change and resource scarcity, and it is a central question in addressing subsoil compaction. Yet how socially acceptable are different methods for subsoil management? Drawing on in-depth interviews with farmers and stakeholders in Germany, we show that biophysical conditions, the timing of operations, economic considerations, and awareness of subsoil functions are key factors in the acceptance of management methods. Views towards methods involving mechanical intervention are more diverse and in some cases more critical because the benefits are not always certain, the costs can outweigh the benefits, and/or because they entail risks for soil structure and functions. Alfalfa cultivation is seen to be beneficial for yields without risks for soil structure and functions; however, economic barriers limit its uptake. Awareness of multiple subsoil functions is associated with more critical views of mechanical interventions.

Root-restricting layers in German agricultural soils. Part II: Adaptation and melioration strategies

“…About 5% of German agricultural land has been deep ploughed at least once in history. Considering that many of today's landowners are highly sceptical about deep ploughing (Frelih-Larsen et al 2018), this share seems relatively large. Many deep-ploughed sites are clustered in northwest Germany close to the Dutch-German border.…”

“…Cultivation of alfalfa and other tap-rooted crops provide a biological alternative to mechanical deep tillage and can improve the plant-availability of water and nutrients in compacted subsoils. Despite of this knowledge, the current share alfalfa in crop rotations is only minor because economic barriers limit its uptake (Frelih-Larsen et al 2018). Financial incentives could help to overcome these barriers.…”

“…The latter has often been neglected in the past, which may explain why many practitioners consider mechanical deep-loosening effects as short-lived while controlled field experiments, which avoided traffic and promoted biological stabilisation show that mechanical loosening can indeed be long-lived (Schneider et al 2017). Traffic-induced re-compaction of loosened soil might be slowed down by incorporating compost and other organic matter-rich substrate into the subsoil (Frelih-Larsen et al 2018;Jakobs et al 2017). However, this management option is still in its test phase.…”

Assessment and Governance of Sustainable Soil Management

“…The utilization of subsoil for root growth and water and nutrient utilization is another key factor of soil-improving agricultural practices [36]. Frelih-Larsen et al [33] analyze determining factors for farmers' decision-making on the implementation of subsoil-improving management practices. These include biological measures such as integrating deep-rooting crops and mechanical practices.…”

Improved Protocol for DNA Extraction from Subsoils Using Phosphate Lysis Buffer

“…In agricultural systems, the distinction between top-and subsoil is made based on the present or historical tillage depth, which is commonly around 20 to 30 cm [1,2]. Although subsoil accounts for the vast majority of agricultural soil [2] and its management becomes increasingly important in light of resource scarcity, [3] our knowledge on soil processes and microbial communities in subsoils is scarce compared to topsoils. Fortunately, however, the number of scientific studies investigating both top-and subsoils is steadily increasing, as the methodologies for such studies become more refined and reliably reproducible.…”