Vali Rasooli Sharabian - Assistant Professor, Department of Mechanical of Biosystem Engineering,University of Mohaghegh Ardabili
Elmira Ghazanfari Jajin - B.Sc in Department of Mechanical of Biosystem Engineering,University of Mohaghegh Ardabili
Asma Kisalaei - M.Sc in Department of Mechanical of Biosystem Engineering,University of Mohaghegh Ardabili
Fatemeh Gholmohammadzadeh - M.Sc in Department of Mechanical of Biosystem Engineering,University of Mohaghegh Ardabili

A ground-based sensor embedded on a tractor for monitoring the growth of winter wheat using a couple plant nutrition active sensors (CropSpec) and RTK-GPS was investigated in this study. In order to consider the reliability of the results, the winter wheat was cultivated. Four levels of N fertilizer were applied to make differences in crop conditionsand growth information was acquired at four growth stages. A strong correlation (R2>0.70) for Nitrogen SufficiencyIndex (S1 value) and ground truth data was found in the second stage of data collection. Also, a strong relationship(R2>0.90) between in-season estimation (INSE) of S1 value and other vegetation indices acquired using a spectroradiometer as a passive sensor demonstrated good performance of CropSpec. However, for diagnosis of crop growth condition for variable rate application, use of the S1 value without elimination of different measurement times is recommended.

remote sensing, active sensor, passive sensor, SPAD value , NDVI,winter wheat