Optimization of Irrigation Requirement of Summer Moong Bean (Vigna radiata L.) under Changing Climatic Scenario of Junagadh District of Gujarat Using CROPWAT Model

Abstract

Summer green gram (Vigna radiata L.) is an important short-duration pulse crop suited to intensive summer cropping systems, but its cultivation in semi-arid environments is constrained by high evaporative demand and limited rainfall. This study estimated crop water requirements and developed an irrigation schedule for summer green gram in Junagadh district, Gujarat, using the FAO CROPWAT 8.0 model. Meteorological data for 2024 and 2025, medium black clay soil characteristics, crop parameters and a sowing date of 23 February were used as model inputs. During the crop period, reference evapotranspiration ranged from 2.78 to 5.17 mm/day. The crop coefficient increased from 0.20 during establishment to a maximum of 1.18 during the mid-season stage, while crop evapotranspiration reached 5.85 mm/day and 58.50 mm/decade. Irrigation demand increased progressively during crop development, peaked during the mid-season stage and declined towards maturity. The model estimated a total net irrigation requirement of 346.6 mm and a total gross irrigation requirement of 495.1 mm. Actual and potential crop water use were 270.5 and 270.8 mm, respectively. Under the simulated schedule, irrigation losses were 0.0 mm, irrigation scheduling efficiency was 100% and seasonal yield reduction was negligible. The findings indicate that stage-specific irrigation scheduling can support efficient water allocation for summer green gram under the agroclimatic and soil conditions considered in the study.