Response of Rice to Sulfur and Zinc Applications Under Fallowed and Continuously Cropped Soils in Northern Ghana

The influence of zinc and sulfur on growth and yield of rice was studied for two soils; fallowed and continuously cropped. It was a 2 x 4 x 4 factorial experiment laid out in a randomized complete block design with three replicates, using lixisols of northern Ghana. Sulfur was applied as Sodium Sulfate (Na2SO4) at 0, 10, 20, 30 kg S/ha, two days after transplanting. Whilst zinc was applied as Zinc oxide (ZnO) at 0, 4, 8, 12 kg Zn/ha before transplanting. All soils received same rates of NPK (90-60-30 Kg/ha). An initial physico-chemical analysis conducted on the soils revealed that, both were sandy loam in texture and low in zinc but moderately high in sulfur. The fallowed soil was high in all other measured soil nutrients except nitrogen when compared to the cropped soil. The experimental results showed that, rice growth (tiller number, plant height), grain yield parameters (panicle count, percentage filled grains, grain yield) and straw yields are maximized by at least inclusion of sole Zn at 8 kg Zn/ha for both soils, with optimum yield recorded under the combined application of 12 kg Zn/ha and 30 kg S/ha for both land use types. Treatments that received 12 kg Zn/ha and 30 kg S/ha had more than twice (50% increase) the yield obtained for treatments that received sole NPK. Yield in both soils responded significantly to additional amounts of sulfur and zinc, indicating that even in a fallowed soil, zinc and sulfur may be inadequate for crop growth, hence their inclusion is needed for better improvement of the rice crop. The fallowed soil recorded the highest grain yield than the continuously cropped soil. The findings revealed the need to consider sulfur and zinc inclusion in NPK fertilizer formulation for maximization of rice production in soils of northern Ghana.