Nitrogen Balance Approach to Sunflower Fertilization

There is very limited information on sunflower (Helianthus annus L.) response to nitrogen (N) fertilizer in comparison to other crops. The N‐balance method has been proposed to estimate fertilizer rates for many crops but this system has not been developed for sunflower fertilization and thus there is a lack of specific parameters for the use of the N‐balance method in sunflower fertilization. The objectives of this experiment were to analyze the response of sunflower yield and yield components to N fertilizer, and to estimate parameters needed to develop a working N balance method. A 2‐year study was conducted in Balcarce, Argentina. Five N fertilizer rates were broadcasted (0, 25, 50, 100, and 200 kg N ha− 1) when the crop reached three pairs of fully expanded leaves. Nitrogen fertilization increased sunflower grain and oil yields, but had no effect on grain oil concentration. A positive response of grain number and grain yield to crop N uptake at the end of flowering was found. In order to maximize yie...