Detecting nitrogen deficiency on irrigated cash crops using remote sensing methods

Early detection of nitrogen deficiency on annual agricultural crops can assist the management of N-fertilization to improve crop yields. Low altitude aerial photography is an inexpensive means to assess crop canopy radiation in the near infrared range. In this study, different Nitrogen experiments were laid out on cotton, tobacco and wheat. Nitrogen rates on the tobacco and cotton were 0.50, 100, 150 and 200 kg N ha1. On a wheat experiment the rates of N were 0.60, 120 and 180 kg N ha−1 with 4 times of application after planting. All these experiments were conducted in 1992 and 1996. Infrared aerial photographs and multi spectral videography were taken of the experiments at certain times using remotely piloted aircraft. These images were processed on a computer and classified into classes of high- and low-N categories using image processing software. A portable spectrometer operating in the 770 nm to 920 mn range was also used to assess N deficiency by measuring the reflected radiation of wheat canopies 7...