Effect of potassium and sulphur nutrition on growth and oil content of sunflower

Abstract:

Sunflower oil quality hinges on two nutrients that many fertiliser programmes overlook: potassium and sulphur. This research examined how four potassium levels (0, 40, 80, 120 kg K₂O ha⁻¹) and three sulphur levels (0, 20, 40 kg S ha⁻¹) affected growth, seed yield, and oil content of sunflower (cv. LS-234) on an alluvial loam near Nanjing, China. The experiment followed a factorial randomised block design with three replications during the 2023 spring season. Seed oil content rose from 31.2% in the unfertilised control to 42.3% at the highest K-S combination (K₃S₄₀), a 35.6% relative increase. Seed yield peaked at 80 kg K₂O + 40 kg S ha⁻¹ (2.86 t ha⁻¹), beyond which additional potassium gave only marginal returns. The K × S interaction was significant for oil content (p = 0.008) but not for seed yield (p = 0.17), suggesting that the two nutrients influence oil biosynthesis through complementary metabolic pathways. These data support including both potassium and sulphur in balanced fertiliser recommendations for oilseed sunflower in the lower Yangtze region.