Abstract
Two years field experiments were conducted on Coastal Plain Sand at Akwa Ibom State University Research Farm, Obio Akpa Campus in 2013 and 2014 to evaluate varietal response of maize, two hybrid (Oba super 1 and 2) and one local variety (Uwep) to residual K fertilization at varying K rates of 0, 30, 60, 90, 120 Kgha-1 K2O. The experiment was set up as a split plot in a Randomized Complete Block Design (RCBD), replicated three times. Main plots comprised five K rates while sub-plots comprised three varieties of maize, no fertilizer was applied in the second cropping season. Some physical and chemical properties of the soil were also determined. The results showed that interaction of Oba super 1 and Uwep with 60, 90 and 120 kgha-1 of muriate of potash were significantly higher (P < 0.05) in terms of plant height, dry matter yield, plant nutrient (N,P,K) contents, total grain yield than others in both 2013 and 2014 cropping seasons. Among the varieties, Oba super 1 performed best at 60 kg ha-1 of K with total grain yield of 6.34 tons ha-1 and the least was Uwep at 60 kgha-1 of K with total grain yield of 4.67 tons ha-1. There was also a residual effect of K in the soil, at 0 kg ha-1 K yield was 2.75 tons ha-1 while 60 kg ha-1 was 5.33 tons ha-1 in 2014, where no treatment was applied and despite the low nutrient status of the studied soils. Farmers are encouraged to grow Oba Super 1 using 60 kgha-1 of K for higher yield.