Optimizing foliar N‐fertilization in sugarcane depends on plant genotype and nitrogen concentration

Abstract Foliar N‐fertilization (FNf) has emerged as a promising approach to synchronize plant nitrogen (N) demands and application timing, reducing the N losses to the environment associated with traditional soil‐based fertilization methods. However, limited information exists regarding the effectiveness of FNf in sugarcane. This study aimed to optimize FNf in sugarcane by evaluating N‐fertilizer recovery by the plant (NRP) and assessing potential toxicity effects. Four sugarcane genotypes were subjected to FNf using 15 N‐urea at five nitrogen concentrations. NRP was assessed at five time points for roots, stalk, old leaves, 15 N‐urea‐fertilized leaves ( 15 NL), and unexpanded leaves (UEL). Leaf scorching, indicating FNf toxicity, was analyzed using morpho‐anatomical and histochemical techniques. The results showed that FNf promoted high NRP, with an average recovery of 62.3%. Surprisingly, the redistribution of 15 N‐urea did not follow the nitrogen uptake rate by sugarcane leaves, with an average of 41.3% of the total‐NRP. The stalk emerged as the primary sink for 15 N‐urea, followed by the UEL. Genotypes differed in the leaf scorching intensity, which increased with higher concentration of 15 N‐urea. Genotypes also differed in the 15 N‐urea uptake rate, down‐regulated by the N content in the 15 NL. These findings emphasize that by carefully choosing the appropriate genotype and nitrogen concentration, FNf can significantly enhance N‐fertilizer uptake, resulting in potential environmental and economic benefits.