Effect of chemical defoliation on boll opening and yield of cotton

Abstract

A field experiment was carried out for two consecutive years kharif, 2014 and 2015 at instructional farm of Rajasthan College of Agriculture, Udaipur, Rajasthan to study the effect of different defoliants at different doses on cotton and residual effect on succeeding greengram crop. The experiment laid out on sandy clay loam soil by adopting randomized block design which included four replication and seven treatments viz. Untreated check, Diquat dibromide 24.5 SL W/V 551.25 g a.i. ha-1 (2250 ml/ha), Diquat dibromide 24.5 SL W/V 735 g a.i. ha-1 (3000 ml/ha), Diquat dibromide 24.5 SL W/V 918.75 g a.i. ha-1 (3750 ml/ha), Diquat dibromide 24.5 SL W/V 1102.5 g a.i. ha-1 (4500 ml/ha), Paraquat dichloride 24 SL 300 g a.i. ha-1, (1250 ml/ha) Mepiquat chloride 5%AS 62.5 g a.i. ha-1 (1250 ml/ha. Variety Super Mallika was taken during kharif season as test crop. Result revealed that application of Diquat dibromide 24.5 SL W/V at 1105 g a.i. ha-1 at 60-70 per cent boll opening stage of cotton crop appears to be promising treatment as it gave significantly higher defoliation, boll opening and seed cotton yield with no phytotoxic effects on cotton bolls and residual crop.