Relation between Early Season–Measured Agronomic Variables and Sugar Yield Responses to Nitrogen

Several studies have demonstrated the use of early‐season plant response to N as a basis for determining N fertilizer requirements in cereal crops. In sugarcane ( Saccharum spp. hybrids) production, the relationship of early‐season growth and responses to N fertilization to sugar yield at harvest has not been pursued. The objective of this study was to evaluate and relate the early‐season response to N fertilization (RI) of select agronomic variables to RI of measured sugar yield at harvest of three sugarcane varieties (HoCP 96‐540, L 01‐283, and L 99‐226). A variety × N (0, 45, 90, and 135 kg N ha −1 ) trial was established at two LSU AgCenter research stations: the Sugar Research Station in St. Gabriel and the Iberia Research Station, Jeanerette, LA, from 2010 to 2012. The positive correlations between RIs of agronomic variables collected at 4 and 5 wk after nitrogen application (WKN) and RIs at harvest were considered notable with RI biomass at 5 WKN obtaining the highest r value (RI sugar = 0.69 and RI cane = 0.68). Sugar and stalk yield increases due to N were also correlated to RI N% and RI Nuptake at 4 to 6 WKN. The findings of the present study demonstrated that RIs of agronomic variables measured early in the season were related with RI at harvest, suggesting the potential use of response to N early in the season as a basis for in‐season determination of sugarcane N rate requirements. Core Ideas Determining seasonal N requirement in sugarcane is essential. High spatial and temporal variability in sugar and stalk yield to applied N were observed. Agronomic variable at early season can be used to predict N response of sugar yield.