Soybean crops with short duration are prone to nitrogen limitation in high-yielding subtropical environments

The asynchrony between soil nitrogen (N) and biological N₂ fixation results in N limitation in soybean crops. The crop duration can potentially alter the asynchrony and N limitation. The objective of this study was to determine the effect of soybean crop duration on N limitation. Seventeen field experiments were conducted in subtropical environments in Brazil with different crop durations: short (102–114 ​d), medium (115–126 ​d), and long (>126 ​d). A full-N fertilizer treatment that synchronized crop N demand and supply throughout crop development was compared with zero-N treatment. Seed yield, protein and oil concentrations, and seed weight and number were determined. The short duration crop was the only one with seed yield response to N supply (0.74 ​Mg ​ha⁻¹; 15.5 ​%). When the long duration crop was fertilized with N, seed protein concentration increased without a trade-off in oil concentration. The N response on seed yield increased by ca. 48 ​kg ​ha⁻¹ per day, when crop duration was shorter than 123 ​d. While the protein yield response increased linearly from long to short crop duration, the oil yield response followed a bi-linear trend. We conclude that N limitation on seed yield in subtropical environments increased as the soybean crop duration decreased below 123 ​d, while the N limitation on seed protein concentration occurred across all crop durations. The intensification of the subtropical soybean-based cropping systems will require increasing soil N to avoid seed protein and yield reductions.