Light interception, growth and yield of compact cotton as influenced by planting geometry, fertilizer levels and growth retardants under high density planting system

A field experiment was conducted at Department of Agronomy, Agricultural College, UAS, Raichur during 2016-17 and 2017-8 to know the effect of planting geometry, fertilizer levels along with growth retardant spray on light interception, growth and yield of cotton grown under HDPS. The experiment was laid out in split plot design consisting of three levels of planting geometries viz., S1: 60 cm x 10 cm (1,66,666 plants ha-1), S2: 75 cm x 10 cm (1,33,333 plants ha-1) and S3: 90 cm x 10 cm (1,11,111 plants ha-1) in main plots and six levels of fertilizers and growth retardants viz., M1: 60:30:30 N:P2O5:K2O kg ha-1, M2: 80:40:40 N:P2O5:K2O kg ha-1, M3: 100:50:50 N:P2O5:K2O kg ha-1, M4: M1 + mepiqnat chloride @ 250 ppm sprayed at 60 DAS, M5: M2 + mepiquat chloride @ 250 ppm sprayed at 60 DAS and M6: M3 + mepiquat chloride @ 250 ppm sprayed at 60 DAS in sub plots. The result revealed that the closer row spacing of 60 cm x 10 cm recorded significantly higher light interception ratio (48.10, 55.46 and 77.83% plant-1 at 60, 90 and 120 DAS, respectively on pooled basis) while wider row spacing of 90 cm x 10 cm recorded significantly lower light interception ratio (40.08, 48.22 and 70.60% plant-1 at 60, 90 and 120 DAS, respectively on pooled basis). Closer row spacing of 60 cm x 10 cm produced significantly higher seed cotton yield (2875 kg ha-1) over other planting geometries. Whereas, the growth attributes viz., number of sympodial branches per plant, total dry matter production per plant and absolute growth rate (13.82, 140.14 g and 1.81 g plant-1 day-1, respectively on pooled basis) and yield attributes viz., number of bolls per plant and boll weight (12.74 and 3.68 g, respectively on pooled basis) were significantly higher at a wider row spacing of 90 cm x 10 cm. Among different fertilizer levels, light interception ratio was significantly higher with the application of 100:50:50 N:P2O5:K2O kg ha-1 ( 47.40, 58.76 and 82.04% plant-1 at 60, 90 and 120 DAS, respectively on pooled basis) and significantly lower was observed with the application of 60:30:30 N:P2O5:K2O kg ha-1 + mepiqnat chloride @ 250 ppm sprayed at 60 DAS (44.15 and 65.74% plant-1 at 90 and 120 DAS, respectively on pooled basis). Application of 100:50:50 N:P2O5:K2O kg ha-1 + mepiquat chloride @ 250 ppm sprayed at 60 DAS recoded significantly higher seed cotton yield (2915 kg ha-1). Further, the same treatment recorded significantly higher growth and yield attributing characters. Lower seed cotton yield was recorded with the application of 60:30:30 N:P2O5:K2O kg ha-1 (2392 kg ha-1). Among the different treatment combinations, a treatment combination of closer spacing of 60 cm x 10 cm along with application of higher fertilizer dose of 100:50:50 N, P2O5 and K2O kg ha-1 recorded significantly higher light interception ratio of 50.53, 61.69 and 85.02 per cent plant-1 at 60, 90 and 120 DAS, respectively on pooled basis. Interaction of a row spacing of 60 cm x 10 cm along with application of 100:50:50 N:P2O5:K2O kg ha-1 + mepiquat chloride @ 250 ppm sprayed at 60 DAS recoded significantly higher seed cotton yield (3178 kg ha-1) followed by combination of a row spacing of 60 cm x 10 cm along with application of 80:40:40 N:P2O5:K2O kg ha-1 + mepiquat chloride @ 250 ppm sprayed at 60 DAS (3031 kg ha-1). While, growth and yield attributing characters were higher under the combination of a row spacing of 90 cm x 10 cm along with application of 100:50:50 N:P2O5:K2O kg ha-1 + mepiquat chloride @ 250 ppm sprayed at 60 DAS.