ABSTRACT
Two different field experiments were conducted at Punjab Agricultural University, Regional Research Station, Bathinda, (1) to manage optimum source-sink relationship through mepiquat chloride (MC) in Bt cotton hybrid and (2) to find feasibility of MC application on non hybrid compact cotton genotype under high density planting system (HDPS) with varied nitrogen levels. Raw data for growth and yield parameters was recorded from each treatment and statistically analysed. In experiment (1), application of MC 75â¯g active ingredient per hectare (a.i./ha) irrespective of splits between 60 and 90 days after sowing (DAS) was effective for significant reduction in plant height, increase in bolls per plant as compared to control and de-topping treatments. All these led to significantly highest seed cotton yield (SCY) and monetary returns under MC 75â¯g a.i./ha as compared to de-topping treatment. In experiment (2) of high density planting of cotton, sympods per plant, bolls per plant, SCY as well as nitrogen use efficiency (NUE) and monetary returns were increased significantly with 25% increase in recommended dose of nitrogen. Among the growth retardants, application of MC 20â¯g a.i./ha once and twice reduced plant height, increased sympods and boll per plant significantly which led to significantly higher SCY production as compared to control. Similarly, NUE and monetary returns were also significantly higher under MC treatments as compared to control. Application of MC 75â¯g a.i./ha in either two or three splits on Bt cotton hybrid under normal plant density and MC 20-40â¯g a.i./ha on non Bt compact genotype under high plant density optimized source-sink relationship which improve crop productivity and profitability.