Effect of growth retardants on morpho-physiological parameters in cotton under irrigated conditions in cotton-wheat system

Growth retardant spray (pix and cycocel @ 50 and 100 ppm) on two cotton genotypes reduced the vegetative growth i.e. leaf area (20–25%) and plant height (9–17%) whereas it increased the reproductive growth i.e. boll weight (5–16%), harvest index (8–12%) and seed-cotton yield (4–9%). The net returns of cotton-wheat system increased by 6%. Two sprays at 90 and 120 DAS in cotton reduced the vegetative growth, yield attributes and seed-cotton yield resulting in less net returns (12% reduction) as compared to one spray. Seed-cotton yield, boll weight and harvest index of LHH 144 were significantly higher (4.5%, 15.8% and 17%, respectively) as compared to F 1861. Growth retardants increased the specific leaf weight (70–80%) resulting in higher leaf chlorophyll content (29–69%). This led to higher photosynthesis (20–22%), photosynthetic radiation use efficiency (22%) and photosynthetic water use efficiency (15–32%). It is revealed that application of pix (50 ppm) in cotton at 90 DAS is useful in controlling excessive vegetative growth and enhancing the yield of cotton under irrigated conditions.