Response of sorghum (Sorghum bicolor) parental lines to split application ofnitrogen

摘要

A field experiment was conducted during the rainy seasons of 2012 and 2013 at the Hyderabad, Telangana, to investigate the optimal timing and proportion of N applications for increasing partial factor productivity (PFPN) of sorghum parental lines. Treatments comprised combinations of 6 parental lines of 3 popular grain sorghum hybrids, viz. 'CSH 14' ('AKMS 14B' and 'AKR 150'), 'CSH 16' ('27B' and 'C 43') and 'CSH 23' ('7B' and 'RS 627') and 4 different times of nitrogen fertilizer application, viz. 50% N at sowing and 50% at 30 days after sowing (DAS), 25% N at sowing + 50% N at 30 DAS + 25% N at boot-leaf stage (BLS-55 DAS), 25% N at sowing + 50% N at 30 DAS + 15% N at BLS-55 DAS + 10% at flowering (70 DAS) and 25% N at sowing + 45% N at 30 DAS + 5% at 45 DAS (foliar spray) + 15% N at BLS-55 DAS + 10% at flowering (70 DAS).These were replicated thrice in a split-plot design. Medium-duration parental lines, viz. 'RS 627', 'C 43' and 'AKR 150' produced the higher leaf-area index (4.14-5.28) than short-duration 'AKMS 14 B' (2.76). Significantly maximum plant height (141 cm), leaf-area index (4.29) and harvest index (25.73%) were recorded with application of 25% N at sowing + 45% N at 30 DAS + 5% at 45 DAS (foliar spray) + 15% N at BLS-55 DAS + 10% at flowering (70 DAS). This treatment also gained a yield advantage of 0.27 t/ha over the control (50% N at sowing and 50% at 30 DAS), and recorded the highest PFPN (68.10 kg grain/kg N applied). The highest net returns (33.60 x 103 /ha) and benefit: costratio (2.08) was however obtained with application of 25% N at sowing + 50% N at 30 DAS + 15% N at BLS-55 DAS + 10% at flowering (70 DAS).