Effect of Light Intensity on the Morpho-physiological Traits and Grain Yield of Finger Millet

The normal light intensity during monsoon season in rainfed finger millet cultivation regions in particular, Bangalore, is around 1200 uMm-2s-1; the effect of reduction in light intensity on physiological parameters and grain yield of finger millet was studied. The experiment was laid out in split plot design with four light intensity treatments and three varieties in three replications. Each replication had four lines of 1.5 m row length (1.5 m x 1.0 m). The crop was directly sown on 03-08-2007 with the spacing of 22.5 cm between rows and 10 cm between the hills, using three varieties namely, GPU-48 (early maturing variety, 100 days), GPU-28 (medium maturing variety, 110 days), and L-5 (late maturing variety, 120 days). Decreased light intensity at canopy level decreased the leaf area, specific leaf weight, net assimilation rate and biomass production, which resulted in decreased grain yield in all varieties. Mean grain yield decreased by 16.4, 34.7 and 55.7% respectively with 75, 50 and 25% light intensity. Low light intensity decreased the biomass, which is important in regional fodder security. Early maturing variety had lesser percent reduction in grain yield (1.68%) as compared to the medium (9.5%) and late maturing (29.0%) varieties at low light intensity of 75 % natural light. Therefore, the critical lower limit of light intensity could be nearly 1200 uMm-2s-1 for finger millet potential yield. The results obtained in this study also suggests that genotypic variability for low light adaptation of early maturing genotype (GPU-48) can be exploited for intercropping systems in rainfed mango plantations up to 4-5 years.