Effect of planting density and nitrogen fertilization on grain yield of hybrid maize

Abstract:

Korean maize yields have stagnated near 5.3 t ha⁻¹ for a decade, even as newer hybrids with higher genetic yield ceilings enter the market. One common explanation is that farmers plant too few seeds per hectare and under-fertilise with nitrogen. This research tested that idea by growing hybrid maize (cv. Kwangpyeongok) at four planting densities (55,000, 65,000, 75,000, and 85,000 plants ha⁻¹) crossed with three nitrogen rates (120, 180, 240 kg N ha⁻¹) in a split-plot design at two locations — Daejeon and Jeju — during 2023. Grain yield peaked at 75,000 plants ha⁻¹ and 180 kg N ha⁻¹ (9.42 t ha⁻¹ at Daejeon; 8.87 t ha⁻¹ at Jeju). Pushing density to 85,000 plants ha⁻¹ lowered yield by 4-7%, while 240 kg N gave no meaningful gain over 180 kg. These results suggest that moderate density increases paired with 180 kg N ha⁻¹ can lift Korean maize productivity without raising input costs.