WHEAT YIELD RESPONSE TO POTASSIUM FERTILIZATION UNDER DIFFERENT NITROGEN AND PHOSPHORUS REGIMES

Rezumat

This study evaluated the effect of potassium fertilization applied under different nitrogen and phosphorus regimes on the grain yield of wheat grown after pea under rainfed conditions at the S.C.D.A 2022-2026. The experiment comprised 16 treatments resulting from the combination of four N-P fertilization regimes (N0P0, N60P0, N60P80, and N120P80) with four K fertilization rates (K0, K40, K80, and K120). Grain yield was determined annually from 2022 to 2026. The topsoil had low inherent fertility and contained 12.5 mg available K₂O per 100 g soil. Meteorological data indicated precipitation deficits in the 2021-2022, 2023-2024, and 2024-2025 agricultural years, whereas 2022-2023 and 2025-2026 received precipitation above the reference average. The unfertilized control produced a mean grain yield of 1.80 t ha⁻¹. The main effect of K was positive, although its magnitude depended on the N-P regime. The highest five-year mean grain yield, 6.86 t ha⁻¹, was recorded for N120P80K80; at the highest N-P regime, K40 and K80 produced nearly identical yields, while K120 provided no additional yield benefit. Five-year mean yields were used to characterize the multi-year response. The results support the need for balanced N-P-K fertilization adapted to soil fertility status and year-to-year variability in environmental conditions.