Influence of plant density on yield of hybrid maize (Zea mays L.) under supplementary irrigation

Maize is an important cereal crop grown in Sri Lanka. Hybrid varieties are popular among farmers and the extent cultivated with hybrids has increased over the last few years. Department of Agriculture released the first local hybrid maize variety (Sampath) in 2004. Agronomic practices recommended for open pollinated varieties are not appropriate for highly input responsive hybrids. Therefore, a study was undertaken at Field Crops Research and Development Institute, Mahailluppallama for two consecutive seasons to determine a suitable plant density for hybrid maize. Four densities namely, 55555 (present recommendation), 74074, 88888 and 111111 plants/ha were tested with two varieties (Pacific 984 and Sampath) at 200kg ha^-1 N, 100 kg ha^-1 P₂O₅ and 50 kg ha^-1 K₂O. Grain yield increases observed in maha 2004/05 for 74074, 88888 and 111111 plants/ha were 88 kgha-1 (2%), 1114 kgha^-1 (21%) and 1708 kgha^-1 (30%) respectively and 247 kgha^-1 (4%), 1434 kgha^-1 (24%) and 1958 kgha^-1 (33%) in yala 2005. Two varieties gave the same yields and variations in leaf area, plant height, ear length and 100 seed weight were found not significantly different. Seed number per ear was reduced by 10-16% at higher densities. Economic analysis revealed that profitability increased by Rs.7000.00- 11,000.00/ha both at 88888 and 111111 plants/ha densities.