Physiological Indices of Direct Seeded Upland Rice (Oryza species) Varieties as Affected by Seed Rates

Field trials were conducted at Samaru and Maigana during the 2011 and 2012 wet seasons on the experimental farm of the Institute for Agricultural Research, Ahmadu Bello University Samaru, Zaria and on the Research Farm of the Kaduna State Agricultural Development Programme, Maigana both in the Northern Guinea Savannah agro-ecological zone of Nigeria to determine the physiological indices of direct seeded upland rice varieties as affected by seed rates. The treatments consisted three sowing methods (Broadcasting, Drilling and Dibbling), three upland rice varieties (NERICA 4, 8 and JAMILA) and three seed rates (40, 80 and 120 kg ha-1). The treatments were laid out in a split plot design and were replicated three times with factorial combinations of sowing methods and seed rates in the main plots and three rice varieties in the sub plots. Results revealed that 40 and 80 kg ha-1 had higher values for CGR, NAR and RGR at both locations. The seed rates of 40 and 80 kg ha-1 significantly delayed heading and physiological maturity at both locations but seed rates did not significantly affect relative growth rate and shoot dry weight at both locations. Sowing method significantly influenced crop growth rate, shoot dry weight and days to 50 % heading only at Samaru where broadcasting and drilling methods recorded higher crop growth and shoot dry weight over dibbling method. However, dibbling method had higher crop growth rate than broadcasting and drilling methods only at Maigana while at Samaru, dibbling delayed in days to 50 % heading. Though dibbling method delayed in days to 50 % heading but was ststistically at par with drilling and drilling in turn was at par with broadcasting method. There was no significant influence of sowing methods on relative growth rate at both locations. There were significant variation and similarity among the varieties used in this study. It was observed that at both locations, JAMILA delayed in days to 50 % heading and therefore matured late while NERICA 8 had the highest crop growth rate and shoot dry weight. However, NERICA 4 and 8 displayed similarities in crop growth and shoot dry weight. Based on the result obtained from the study, it can be inferred that JAMILA matured later than NERICA 4 but had higher physiological indices in Samaru while NERICA 8 perform better in Maigana. Consequently broadcast or drilled rice performed better at 40 kg ha-1 seed rate.