Growth, yield and quality of Bt cotton hybrid under varied planting patterns, NPK levels and season variations.

Abstract

A field trial was conducted during two consecutive fall seasons of 2003–04 and 2004–05 to study the effect of three planting patterns and three NPK levels on Bt cotton under irrigated situation at semi-arid condition of Coimbatore. Existing planting pattern, viz 90 cm × 60 cm for Bt hybrid adopted from the conventional hybrid was below optimum from the stand point of morphology and yield formation. Bt hybrids planted at wider spacing produced relatively lesser values in parameters of growth, viz leaf area index and total biomass, and seed cotton yield. Since Bt hybrid is compact in its growth habit favouring higher plant population achieved at a spacing of 75 cm × 60 cm was optimum for realizing higher seed cotton yield. Similarly, the existing NPK level recommended for conventional hybrids was not adequate for Bt hybrids as evident from lesser growth, lower reproductive counts and decrease in seed cotton yield. Thus, crop requirements for NPK in excess of 25–50% could help in realizing higher dry weights and yields. On economic front, highest gross returns (` 46 000/ha), net returns (` 22 373/ha) and benefit: cost ratio (1.9) were realized with 75 cm × 60 cm spacing. Application of 150% of NPK (135:67.5:67.5 kg(` 45 400/ha), net returns (` 21 148/ha) and benefit: cost ratio (1.8). Effect of seasonal variation on Bt cotton showed that high rainfall received early in the season during 2003– 04 influenced positively towards better crop growth and development that led to realization of higher yield. of N, P2O5 and K2O/ha) calculated the highest gross returns