Impact of Foliar and Soil Application of Potassium on Wheat Growth and Yield Under Full and Limited Irrigation

Wheat productivity in Pakistan remains below potential due to nutrient deficiencies and limited water availability. The comparative role of soil and foliar applied potassium (K) under different irrigation regimes is not well established. This study was conducted at the Agronomy Research Farm, The University of Agriculture Peshawar, during the 2023–2024 to evaluate the influence of K application on wheat growth and yield under full and limited irrigation. The experiment was arranged in a randomized complete block design with three replications. Two irrigation regimes were imposed: full irrigation (four irrigations at emergence, tillering, booting and grain filling) and limited irrigation (two irrigations at emergence and booting). Treatments consisted of soil-applied K (75, 100 and 125 kg ha-1), foliar-applied K (1, 2 and 3%) and a control without K for each replication under both fields, using sulfate of potash (SOP) as the source. Application of 125 kg K ha-1 improved emergence (91 m-2), plant height (86 cm), spike density (306 m-2), grains spike-1 (60), thousand grain weight (41.14 g), biological yield (11,322 kg ha-1), grain yield (3,377 kg ha-1) and harvest index (30 %) comparable with 100 kg K ha-1. Foliar K at 2–3% enhanced emergence, leaf area and yield traits with 2% producing maximum thousand grain weight (41.64 g). Full irrigation significantly outperformed limited irrigation, while treated plots consistently exceeded controls. It is concluded that soil K at 100 kg ha-1 combined with 2% foliar K is a promising strategy to improve wheat productivity under both irrigation regimes in Peshawar.