Effect of topping under different nitrogen levels on agronomic characters of cotton

An experiment was conducted to study the effect of topping under different nitrogen levels on growth, yield and quality of cotton (Gossypium hirsutum L.) (Bt. Cotton) at Agronomic Research Area, University of Agriculture, Faisalabad, during kharif 2017. The experiment was laid out in Randomized Complete Block design (RCBD) with factorial arrangement having three replications. Treatments included; A) Four topping levels; control (No topping), topping at 90 cm, 120 cm and 150 cm height, B) Three nitrogen levels; 150 kg ha, 200 kg ha and 250 kg ha. Upper 3-4 cm portion of terminal bud of main stem was removed when plant height was 3-4 cm more as per treatment to maintain the height of plants as per treatment (70-100 days after sowing) by regular visits. All other agronomic practices were kept normal and uniform. The data regarding the agronomic parameters were collected and statistically analyzed using Fisher’s analysis of variance technique and the treatments’ means were compared by using Tukey’s HSD (Honestly significant difference) test at 5% probability. Effect of nitrogen rate, topping as well as their interactive effect was significant on total number of bolls per plant. A comparison of all interaction values showed maximum total number of bolls per plant in plots where plants were applied with 250 kg N ha and topping was done at 150 cm height which were equal to the total number of bolls per plant in plots where plants were applied with 200 kg N ha and topping was done at 120 cm height. While significantly less total number of bolls was recorded when no topping was done and topping was done at 150 cm height when plants were applied with 150 kg N ha. Effect of nitrogen rate and topping was significant but their interactive effect was non-significant on number of aborted sites per plant. As we increased nitrogen above 200 kg ha number of aborted sites per plant also increased. As plant height increased number of aborted sites per plant also increased. Effect of nitrogen rate and topping was significant but their interactive effect was non-significant on number of infested bolls THE INTERNATIONAL JOURNAL OF BIOLOGICAL RESEARCH (TIJOBR) ISSN Print 2618-1436 ISSN Online 2618-1444 Volume 2, 2019 RESEARCH ARTICLE