Integrating satellite data with a Nitrogen Nutrition Curve for precision top-dress fertilization of durum wheat

The present study developed a method to use RapidEye satellite information for N management in durum wheat cultivation. The estimation of the N status was based on the development of Nitrogen Nutrition Index (NNI), referred to as the ratio between actual N concentration (N-ac) and the minimum N content required to obtain maximum biomass (critical N concentration (N-c)). N-c was then calculated by means of a N-c dilution curve, which was calibrated through the use of durum wheat experimental fields (the number varying per year) in Val D'Orcia area (Tuscany) over three consecutive growing seasons from 2009/2010 to 2011/2012, respectively. The data (N-ac and biomass) to produce estimated NNI were obtained by matching the available field samples with information obtained from remote sensing. Statistical analysis indicated that both modified chlorophyll absorption in reflectance index (MCARI) and enhanced vegetation index (EVI2) were the best vegetation indices (VIs) for estimating N-ac and biomass, respectively. The validation, attained using the 2012/2013 experimental field data, showed that the proposed model was very reliable. This could be an effective method in advising farmers on the application of midseason N fertilization treatments, through precision farming operations.