Narrowing the ecological yield gap to sustain crop yields with less inputs

Sustainable production of sufficient and healthy food requires efficient use of agricultural inputs. In many regions of the world with intensive agriculture and relatively small yield gaps, this calls for a reduction of external inputs (fertilizers and pesticides) while maintaining yields. Ecological intensification, defined as the use of practices that enhance on-farm ecosystem services to reduce external input requirements, has been proposed as a strategy to help achieve this. However, the effects of ecological intensification are context- and input-dependent, creating uncertainty on its effectiveness and feasibility. Here, we introduce the concept of an ‘ecological yield gap’ to provide a common analytical framework to strengthen collaboration between agronomists and ecologists in assessing the contribution of ecosystem services within the wider array of inputs, management practices, technologies, and biophysical limits that determine on-farm crop yields. We define the ecological yield gap as the yield increase that could be achieved in a given context (climate x soil x cropping system), and at a given input level, by increasing the delivery of ecosystem services via ecological intensification practices that support crop growth and substitute external inputs. We provide empirical examples of such practices, including crop diversification, service crops, and organic amendments that can increase the use efficiency of mineral fertilizers and suppress pests, weeds and diseases. The potential of these practices to narrow the ecological yield gap and their feasibility at farm level depend on how the ecosystem services they provide interact with other aspects of the farming system and requires analysis at farm level. This perspective paper aims to facilitate a shared research agenda among agronomists and ecologists to develop complementarity between ecosystem services and inputs at field and farm levels.