a Satellite view (Googlemap) of low-N fields at the CIMMYT Harare station, b Spectral reflectance of wheat plants grown at high density on the low-N fields prior to booting. (filled purple square and filled pink square indicate very low nitrogen and relatively higher nitrogen levels, respectively). The fields were depleted of soil N for (1) 5 years and (2) 4 years by growing maize without any N application. c Multispectral images showing management related field variability of low-N fields at the CIMMYT Harare station planted with maize trials. A, a High variation in a poorly managed field and B, b well-managed field.