Fertilizer is the basic input for sustainable crop production for the growing World under the current cropland. Among macronutrients, potassium contributes greatly to plant growth, development and yield. Evaluating the effect of potassium (K) on hybrid maize (CS-200), a field trial was therefore designed and conducted at agronomy research farm during kharif  2017 and 2018 at The University of Agriculture Peshawar. Different K sources i.e.  potassium chloride, potassium sulfate, poultry manure, farm yard manure and potassium doses i.e. 30, 60, 90 and 120 kg K ha^-1 were investigated by using RCB design with four  replicates. One control replication^-1 was kept for its comparison with rest treatments. Seeds sowing was done in rows 70 cm apart with 25 cm inter plant spacing with in the row. Potassium chloride significantly improved grains cob^-1 (394.35), heavier grains (298.37 g), more grain yield (4949 kg ha^-1), while both organic sources exhibit statistically similar grains cob^-1 (383.60), grain weight (282.82 g) and grain yield (4356 kg ha^-1). Potassium chloride exhibits more protein content of the grain (9.21 %), more grain K (0.54 %), higher soil available K (158.91 mg kg^-1), higher leaf water content (91.53 %) and reduction in water lost after 90 minutes (61.93 %) interval. Potassium supplied at 120 kg K ha^-1 produce heavier grains (297.18 g), more grain nitrogen (1.63 %), grain protein (9.29 %), soil available K (162.39 mg kg^-1) and more leaf relative water status (90.34 %). Statistically similar results for 90 and 120 kg K ha^-1 was noted for grain yield (4859 kg ha^-1), grains K content (0.59 %) and reduction in water lost from cut leaf surfaces after 90 minutes (60 %). Potassium chloride enhanced yield, yield components, physiology and grain quality significantly along with maximum net returns (PKR 197718/- ha^-1) with maximum VCR value (4.53). Potassium applied at 90 and 120 kg K ha^-1 enhanced yield, growth, yield components, physiology and grain quality. Application of potassium at 90 kg ha^-1 from potassium chloride was economical for enhancing growth, phenology, yield, yield attributes, physiology, grain quality and is thus recommended for cultivation of maize under the climatic conditions of Peshawar valley.

Keywords: Relative water content, excised leaf water loss, yield, grain quality.