Soil organic amendments for restoring degraded drylands: strategies, recommendations and challenges for large-scale application

Soil is an essential and non-renewable resource in natural and agricultural ecosystems with extremely slow formation and regeneration potential. In dryland areas, many ecosystems are being seriously affected by degradation processes because of an excessive use of agro-chemicals, deep tillage and intensive irrigation, among many other factors. The decline in soil organic matter is also becoming a major cause of soil degradation, particularly in dryland regions where low soil fertility cannot always maintain a sustainable production. The use of organic amendments in ecosystem restoration programs can be an effective technique for promoting soil restoration processes in degraded drylands and several studies have shown their benefits for improving soil physical, chemical and biological properties. This recovery is a result of the rapid increment of organic matter and clay contents in the soil in the short term. In the long-term, soil structure becomes more stable and water holding capacity, permeability and infiltration are improved, whereas surface runoff and erosion are reduced. Nevertheless, there are many research gaps in the knowledge of the effects of climatic conditions on their application, as well as the adequate types of amendment and doses and decomposition rates. In this presentation, we evaluate the role of organic amendments as an effective strategy in dryland restoration, highlighting the effects of different amendment types, doses and application rates. We will specifically address: (1) type of amendments and benefits arising from their use, (2) application methods and more appropriate doses and, (3) potential risk derivates for their application. We also showcase some recent case studies using organic amendments in degraded dryland areas from Spain and Australia.