As environment pollution concerns, crop variable nitrogen (N) management in agriculture has been a critical topic in modern scientific world. For variable N management, crop N diagnosis is the core issue. Many parameters were suggested for indicating crop N status. Among them, it has been documented that Nitrogen Nutrition Index (NNI) can be a valuable candidate, recently. However, measurement of NNI relies on tedious sampling and laboratory analysis. Achieving its remote detection would be great help for variable N management, since such measurements are not invasive and can be repeated several times during the growth period.

A research group led by Dr. CHEN Pengfei and Prof. SUN Jiulin, from Institute of Geographic Sciences and Natural Resources Research (IGSNRR), CAS and other institute, has engaged in the study of NNI remote detection and its application in variable N management.

During recent study, the group developed a new nitrogen concentration index, named Double-peak Canopy Nitrogen Index (DCNI), using hyperspectal remote sensing data. Based on the use of a wide rang of corn date[4 years, different growth stages (V5-VT)], two crop species (corn and wheat), ground-based reflectance spectra, airborne imagery and the comparison of many spectral indices, DCNI was determined as the best index for estimating plant N concentration. It was the most sensitive to N concentration changes during the critical N management stage (V5-VT) of corn and can be used both for corn and wheat N concentration estimation. In conjunction with some indices designed for biomass estimation, DCNI may be instrumental in the evaluation of NNI by remote sensing.

In addition of above results, researchers have conducting field experiment to study the effects of using NNI for winter wheat variable N management. It is expected some good result will be obtained after next growth season.

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