A field experiment was conducted during rainy (kharif) season of 2000 to 2003 for successive four years to study the effect of foliar nutrition of potassium nitrate (4 levels: 0.2, 0.4, 0.6 and 0.8%) along with water spray (control) on greengram var. K 851 on Vertic Ustocrepts soils at Dry Farming Research Station, Targhadia (Gujarat). Foliar application of potassium nitrate was significantly affected the relative water content (RWC) at 10 days after flowering (DAF). The higher values of RWC at maturity, pod growth rate (PGR), crop growth rate (CGR) and partitioning percentage were recorded due to foliar application of potassium nitrate as compared to water spray only. Foliar application of potassium nitrate @ 0.4% significantly increased grain yield by 18.4 per cent as compared to water spray only and also gave higher economic benefits of Rs. 2043/ha over that of water spray.