Canopy reflectance, stalk sugar and juice yields in specialty corn hybrids as affected by nitrogen management strategies

BACKGROUND The newly developed sugarcorn is conceived for dual‐purpose use as a potential biofuel feedstock and a high‐energy silage crop. Its agronomic traits are, however, not fully appraised under the umbrella of nitrogen (N) management and with canopy reflectance indicator. A 3‐year field study was conducted to examine the responses of silage biomass, stalk sugar concentration, sugar and juice yields to various N applications; and determine the quantitative relationships between canopy reflectance, expressed as the normalized difference vegetation index (NDVI), and stalk sucrose or other sugar measures in a dual‐purpose sugarcorn (cv. ‘CO384xC103’), in comparison with a commercial leafy silage‐specific hybrid (cv. ‘Pride A5892G3 EDF’). RESULTS The moderate N rate, 125 kg ha −1 , produced similar stalk sucrose, silage and grain yields, compared to the high rate (250 kg N ha −1 ), regardless of application methods. The NDVI signatures measured at the V8–V10 stage exhibited significant ( P  < 0.01) and exponential relationships with stalk sucrose concentrations, sucrose and juice yields at the R3 stage, and with silage yield at approximately 65% whole‐plant moisture, the optimum silage‐harvest window. CONCLUSION The results indicate that the moderate N rate, 125 kg ha −1 , which is recommended for conventional grain corn production in the region, was likely close to the economic optimum N rate for leafy silage‐specific and sugarcorn. Canopy reflectance, measured at the early growth stages, can be used as a potential indicator of sugar and silage production, and this quantitative relationship necessitates further evaluation with more genotypes and under wide environmental conditions. © 2019 Her Majesty the Queen in Right of Canada Journal of The Science of Food and Agriculture © 2019 Society of Chemical Industry