RESPONSE OF KHARIF MUNGBEAN (VIGNA RADIATA L. WILCZEK) TO GRADED LEVELS OF POTASSIUM FERTILIZATION ACROSS EIGHT AGRO-ECOLOGICAL LOCATIONS OF PUNJAB, PAKISTAN

Abstract

Mungbean (Vigna radiata L. Wilczek) is the most important Kharif pulse crop of Pakistan, yet on-farm yields across Punjab remain well below the genetic potential of currently released varieties. The persistent yield gap has been linked to the widespread practice of growing mungbean as a low-input crop on residual soil fertility, with little or no application of macronutrients other than starter nitrogen. The present study was conducted under the Soil Fertility Punjab research project PLAN-10 to evaluate the response of Kharif mungbean (cv. AZRI-Mung 2021) to graded levels of soil-applied potassium fertilization at eight agro-ecological locations of Punjab during the 2024 Kharif season. Six treatments; an absolute no-fertilizer control (T1); a nitrogen–phosphorus basal alone (T2; 62.5 kg N + 86 kg P2O5 ha-1 ); and four NP plus graded K2O treatments at 30, 40, 50, and 60 kg K2O ha-1 supplied as sulphate of potash (T3– T6), were arranged in a randomized complete block design with three replications at each site. Combined analysis of variance revealed highly significant effects of location, treatment, and their interaction on both grain yield and thousand grain weight (p < 0.01 for all terms). Pooled across the eight sites, grain yield rose progressively from 841.6 kg ha-1 at the absolute control to 1,265.6 kg ha-1 under the NP basal alone (+50.4%) and to 1,545.8 kg ha-1 at the highest K rate (+83.7% over the absolute control, and a further +22.1% over the NP-only baseline). The yield response was monotonically positive at every site, peaked at 60 kg K2O ha-1 in all eight locations, and showed no evidence of a plateau. The site-wise yield gain over the absolute control ranged from +505 kg ha-1 at Bhakkar to +890 kg ha-1 at Faisalabad. On this evidence, the inclusion of 60 kg K2O ha-1 as a basal soil-applied input (alongside 62.5 kg N + 86 kg P2O5 ha-1 ) is recommended as a regional fertilization practice for Kharif mungbean across Punjab; the still-rising response curve further suggests that even higher K rates warrant testing on these soils.