Density and Cultivar Effects on the Biomass and Crop Growth Rate of Upland Rice in Uyo Southeastern Nigeria

Aims: To evaluate population densities and cultivars on the biomass and crop growth rate (CGR) of upland rice and their correlation with grain yield.

Study Design: A Factorial on randomized complete block design.

Place and Duration of Study: The Teaching and Research Farm of the Faculty of Agriculture, University of Uyo, between May 12, 2009 and September 30, 2010.

Methodology: Six sowing densities; 1,600,000, 1,066,666, 800,000, 640,000, 533,333, and 2,054,435 plants ha-1 were combined with five cultivars of rice; FAROs 43, 46, 55, 56 and a local cultivar – Otokongtian. Treatment combinations were replicated three times. Destructive samples were collected at 3, 6, 9, 12, and 15 weeks after sowing (WAS), oven-dried at 80°C to constant weight and the biomass and CGR determined. Data were analyzed with Genstat Discovery Edition 4 and means compared by Fisher’s protected least significant difference at 5% probability.

Results: Rice biomass for 2,054,435 and 1,600,000 densities increased significantly (8.77-12.55 and 7.08-11.44 g m-2) at 3 WAS in 2009 and 2010 respectively (P=.05). Biomass increase was highest at 15 WAS across densities and cultivars in both years. FARO 46 produced the highest significant biomass in both years during the period but was replaced by Otokongtian at 15 WAS. At 3-6 WAS, 2,054,435 produced the highest significant CGR in both years (5.83 and 5.193 g m-2 day-1 for 2009 and 2010 respectively), while FARO 43 had the highest CGR during the period. Higher densities produced higher CGR. The CGR continued to increase across densities and cultivars up to 9-12 WAS and began to decline at 12-15 WAS. There was a positive correlation between rice biomass, CGR and grain yield.

Conclusion: Higher sowing densities produced higher rice biomass and CGR which correlated positively with grain yield.