The yield gap is the difference between the actual productivity of a given area of farmland and the maximum productivity that could in principle be achieved using agricultural practices, resources, and technologies that are currently available. The best yields that can be obtained locally depend on the capacity of farmers to access and use, among other things, land, seeds, water, nutrients, pest management, soils, biodiversity, and knowledge. Yield gaps are studied and measured at various scales - from the farm through to the national and global levels.