Estimation of foliar nitrogen using remotely sensed data: A quantitative review

Several ecosystems have been significantly altered by anthropogenic nitrogen inputs. The timely estimation of nitrogen concentration is essential for ensuring environmental sustainability. Academic publications between 1966 and 2016 were reviewed to assess the potential of remotely sensed information to estimate nitrogen concentrations for various applications. A discriminatory keyword search and a set of inclusion criteria was used to develop a representative sample (n = 100). Results revealed that the global distribution of academic publications is skewed towards the Northern Hemisphere with the largest research gap occurring within Africa. Moreover, prior to 2006, research into the remote estimation of nitrogen had a minor presence in literature, with the agricultural sector being the most extensively researched (56%). Freely available, high spatial and temporal resolution imagery has afforded research into the remote estimation of nitrogen in the African continent, particularly in the subject area of policy and management, the capacity to grow.