Reflectance indices with precision and accuracy in predicting cotton leaf nitrogen concentration

• Published in: Crop science 2000-11, Vol.40 (6), p.1814-1819
• Main Authors: Tarpley, Lee, Reddy, K. Raja, Sassenrath-Cole, Gretchen F.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Cotton; Cotton growing; Crops and nitrogen; Fertility; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Growth chambers; Leaves; Nitrogen; Nitrogen fertilization; Nitrogen in agriculture; Nitrogen, phosphorus, potassium fertilizations; Optical properties; Reflectance; Soil-plant relationships. Soil fertility. Fertilization. Amendments
• ISSN: 0011-183X; 1435-0653
• DOI: 10.2135/cropsci2000.4061814x

Diagnostic methods assaying leaf optical properties can aid rapid site‐specific screening of crop nitrogen status. A set of calibration curves relating many 1.5‐nm band reflectance ratios to cotton (Gossypium hirsutum L.) leaf N concentration was established from plants grown in sunlit growth chambers and at a range of nitrogen levels. Predicted and actual concentrations were compared by regression for a validation set of field‐grown leaf samples from diverse genotypes. Only those ratios that combined a red‐edge measure (700 or 716 nm) with a waveband of high reflectance in the very near infrared region (755–920 and 1000 nm) provided good precision (correlation) and accuracy (one‐to‐one relationship between predicted to actual values). Other indices that included a chlorophyll‐based reflectance feature also had good precision but were less accurate than those obtained from the red‐edge/very‐near‐infrared reflectance ratios.