CRITERIA FOR SCHEDULING THE IRRIGATION OF MUSTARD (BRASSICA-JUNCEA L)

Field experimentation was conducted during two seasons to evaluate criteria for irrigation scheduling of mustard (Brassica juncea L.). The irrigation treatments were applied according to physiological stages and pan evaporation. An increase in the irrigation frequency, either based on physiological stages or pan evaporation, resulted in greater leaf area index (LAI), branches per plant, xylem pressure potential, relative water content, and seed yield of mustard. The evapotranspiration (ET) of the crop increased as the crop season advanced and reached its peak from 30 to 60 days after sowing (DAS). The profile water use and seed yield varied from 24.1% to 72.6% and from 710 kg ha-1 to 1378 kg ha-1, respectively, depending upon the irrigation scheduling. Multiple regression analysis revealed that the highest obtainable yield of 1529 kg ha-1 was found to be at an LAI of 7.07 and an ET of 235.02 mm when two irrigations were applied based on pan evaporation. The water use efficiency decreased with increasing ET levels at all LAI. The crop coefficient (K(c)) to compute crop water use from pan evaporation varied between 0.19 and 1.14.