Rethinking soil water repellency and its management

Abstract

Soil water repellency (SWR) is a widespread challenge to plant establishment and growth. Despite considerable research, it remains a recalcitrant problem for which few alleviation technologies or solutions have been developed. Previous research has focused on SWR as a problem to be overcome, however, it is an inherent feature of many native ecosystems where it contributes to ecosystem functions. Therefore, we propose a shift in the way SWR is perceived in agriculture and in ecological restoration, from a problem to be solved, to an opportunity to be harnessed. A new focus on potential ecological benefits of SWR is particularly timely given increasing incidence, frequency and severity of hotter droughts in many regions of the world. Our new way of conceptualising SWR seeks to understand how SWR can be temporarily alleviated at a micro-scale to successfully establish plants, and then harnessed in the longer term and at larger spatial scales to enhance soil water storage to act as a "drought-proofing" tool for plant survival in water-limited soils. For this to occur, we suggest research focusing on the alignment of physico-chemical and microbial properties and dynamics of SWR and, based on this mechanistic understanding, create products and interventions to improve success of plant establishment in agriculture, restoration and conservation contexts. In this paper, we outline the rationale for a new way of conceptualising SWR, and the research priorities needed to fill critical knowledge gaps in order to harness the ecological benefits from managing SWR.

Developing extruded seed pellets to overcome soil hydrophobicity and seedling emergence barriers

“…Further investigation into the development of products to help ameliorate SWR at the micro‐scale is required (Ruthrof et al., 2019). With greater knowledge of this abiotic barrier arising, there are greater innovative opportunities to refine seed enhancement technologies.…”

“…In the process of making pellets, for instance, the dough that is formed can be created with a multitude materials, that depending on species and site conditions (i.e. clays, binders, inoculums, bio stimulants) can be tailored to aid in seed germination, seedling emergence and early plant growth (Madsen & Svejcar, 2016; Madsen et al., 2016; Ruthrof et al., 2019). From this initial pilot study, optimal testing of surfactants (e.g.…”

“…Despite considerable research, it remains a problem for which few mitigation technologies or solutions have been developed with success in agricultural or restoration activities (Ruthrof et al., 2019). Extruded pellets that contain soil surfactants is an emerging technology in restoration activities that is being developed to deploy and improve native plant establishment within degraded landscapes including overcoming SWR in North America's sagebrush biome (Davies, Boyd, Madsen, Kerby, & Hulet, 2018; Davies, Madsen, & Hulet, 2017; Madsen et al., 2016; Madsen et al., 2016).…”

“…High seedling mortality due to extremely water‐repellent soils and drought are key limiting factors of restoration success in Western Australia and other Mediterranean ecosystems (McGhie & Posner, 1980; Padilla & Pugnaire, 2007; Roberts & Carbon, 1972). SWR need only to be temporarily alleviated to ensure successful establishment of plants and then SWR can be utilized to provide natural ecological benefits such as improving soil water conservation (Ruthrof et al., 2019).…”

“…Soil water repellency (SWR) can be a major constraint to plant establishment and growth (Ruthrof et al., 2019). As a global phenomenon (Dekker, Ritsema, Oostindie, Moore, & Wesseling, 2009; Doerr, Shakesby, & Walsh, 2000), it can negatively affect the establishment of plants in agricultural systems (DeBano, 2000), particularly during restoration (Madsen et al., 2012).…”