Using waste soil to rehabilitate degraded agricultural lands: environmental burden as resource

The global expansion of infrastructures is generating vast amounts of waste soil (soil excavated from construction sites that cannot be used on-site); the amount of waste soil accumulated in the European Union in 2014 was estimated at 463 x 10⁶ tons. The regulation and management of waste soil disposal are currently limited to: (1) local use for various engineering projects; (2) stockpiling on-site for future use; (3) transferal to landfills, which are currently overfilled, as padding material or for disposal. Despite a number of permitted actions for handling waste soil, a significant portion of it is disposed of in the area surrounding the construction site, thus raising the risk of pollution and landscape spoilage. Waste soils are commonly excavated from deep layers, and are therefore saline, sodic, and lack organic matter, preventing their use without pre-treatment. Moreover, due to the intensification of crop production, one-third of the global agricultural land area is susceptible to soil loss by erosion, constituting ~50% of total estimated soil erosion. Here we show a new approach for environmentally, agronomically and economically sustainable use of reclaimed waste soil to rehabilitate degraded agricultural land. In a 3-year field experiment under rain-fed conditions in a semi-arid region of Israel, we found that waste soil ploughed into agricultural soil had low erodibility, similar to that of the original agricultural soil, despite its high sodicity. Waste soil application tended to decrease the soil organic carbon concentration but had no detrimental effect on wheat hay yield or wheat grain yield or quality in the second and third year, respectively. The economic analysis suggested an average reduction of 8.7 million USD in waste soil disposal costs if 50% of the waste soil produced in Israel annually were to be utilized in agricultural fields. Thus, waste soil can be utilized successfully in degraded agricultural lands; this opens a new route to land reclamation and provides land managers and stakeholders with a sustainable way to reduce costs while transforming an environmental burden into a resource.