Potassium application timing to improve corn K-fertilizer use in the oat-corn sequence: a tracer study for high yielding corn

Corn performance is often unchanged by modifying the potassium fertilizer application timing, especially when soil K is not a limiting factor. Consequently, there is no literature reporting K timing on K-fertilizer contribution (or use) in high-yielding corn fields. We evaluated corn performance and K-fertilizer use based on timings of K-fertilizer application in the oat-corn sequence at subtropical environment with highly weathered soils. Additionally, we propose a timing strategy to ensure high corn use of fertilizer. The crop sequence study was conducted in two field experiments to investigate corn performance with respect to K-leaf, K uptake, and yield. Additionally, we evaluated K-fertilizer use by rubidium as potassium derived from fertilizer and potassium use efficiency. Application timings were two before and three during corn growth and development. Timings did not change corn performance even for late K application, and this was attributed mainly to soil K sufficiency levels. Corn K-fertilizer use, on the other hand, was different and higher for timings before (versus during) corn growth and development. Importantly, timing of K application similar to 22 days before corn sowing improved corn K-fertilizer use approximately 2-fold versus the two late timings. Timings in oat or during corn sowing were identical for corn K-fertilizer use. We link our rainfall data with literature K-fertilizer movement (positional aspect), and the corn ability to acquire it. Application of K at 3-weeks before corn sowing constituted the optimal timing for fertilizer supply. This finding will assist farmers in large-scale areas to manage K-fertilizer application to promote higher efficiency.