Irrigation Amounts and Timing of Irrigation Termination Affecting Mungbean on a Silty Clay Loam Soil

Abstract

Responses of a mungbean cultivar, Chai Nat 36, to irrigation level and timing of irrigation termination were examined on a silty clay loam soil at Chai Nat Field Crop Research Centre in 1995 and 1996. The number of irrigation applications were 2-5 and 2-4 for the 1995 and 1996 experiments respectively, and total amounts of water were 12-216 and 12-192 mm, depending upon irrigation rates and timing of last irrgation. There were no interactions between irrigation amounts and timing of irrigation termination in both seasons. Leaf area index (LAI),leaf area duration (LAD) and crop growth rate (CGR) increased with increasing irrigation rates up to the highest rate, IW/E (ratio of irrigation water to evaporation) 0.8. Irrigation applied through R5 gave the greatest LAI, LAD and CGR, whereas irrigation terminated at V4 showed the lowest. Seed yields increased up to 53% with increasing irrigation rates from IW/E 0.1 to 0.8. Irrigation terminated at V4 reduced seed yields 18 and 44% as compared to irrigation terminated at R1 and R5, respectively. Reduction in the number of pods/plant and seeds/plant and seeds/pld was the major factor causing a smaller yield of lower irrigation rates and irrigation terminated at early growth stages.