Ecological intensification of agriculture in drylands

Drylands, which represent the world largest biome and support approximately 38% of the global human population, offer harsh climate and poor soil for agriculture. These environmental conditions are expected to get even harsher with climate change, challenging the potential to close the yield gap in these areas. In this short review, we focus on ecological intensification, which aims to replace external agricultural inputs (e.g. inorganic fertilizer) with fanning practices optimizing ecosystem services beneficial for crop yield. We first highlight important management goals for dryland agriculture sustainability, then identify two practices of ecological intensification (conservation agriculture and intercropping) that can help to meet such goals, and finally propose guidelines for future research. The temporal stability of crop yield and its nutritional diversity, besides total yield, are key components of crop production in dryland agriculture. Conservation agriculture and intercropping seem adequate to foster crop yield in drylands, via increased soil carbon accumulation, water and nitrogen retention, if they are adapted to the particular climatic and socioeconomic conditions found in these areas. Yield stability is not affected by conservation agriculture, and there are not enough studies conducted in drylands to evaluate the stabilizing role of intercropping. To move this field forward in dryland areas, we propose multi-functional approaches integrating trade-offs between crop yield and ecosystem services, long-term studies addressing the independent contribution of the different conservation agriculture components, and identification of crop mixtures with an optimal distribution of plant functional traits.