ABSTRACT

Field and laboratory studies were carried out in 2018 and 2019 at the National Root Crops Research Institute Eastern Farm, Umudike to explore the influence of mineral and organic fertilization on forms of potassium and ginger production in an Ultisol of Southeastern Nigeria. There were ten treatments consisting of sole and combined application of cow dung, poultry manure, rice mill waste, sawdust and NPK 15:15:15 at the rate of 45 kg N/ha regarded as 100%. They were arranged in a randomized complete block design with three replications. Ginger variety (UG I) was used for the experiments. The soil chemical properties and different forms of K were determined at 5 and 8 months after planting (5 and 8 MAP). The potassium uptake in ginger leaf and yield at 5 months after planting (5 MAP) and in the rhizome at 5 and 8 months after planting (5 and 8 MAP) were equally determined. Results showed that the application of the treatments significantly (p<0.05) increased soil chemical properties with the application of 100% NPK giving the highest values for most of the parameters determined at 5 MAP and it was closely followed by plots treated with 50% NPK + 50% rice mill waste in the two planting seasons. At 8 MAP (final harvest) plots treated with 50% NPK + 50% poultry manure gave the highest values for most of the parameters determined in the two planting seasons. The results showed that the application of the treatments significantly (p<0.05) increased the forms of K with plots treated with 100% sawdust giving the highest water soluble K at 5 and 8 MAP in 2018 and 2019 respectively. The plots treated with 100% NPK and 50% NPK + 50% cow dung gave the highest exchangeable K at 5 MAP in 2018 and the plots treated with 100% NPK and 50% NPK + 50% poultry manure gave the highest exchangeable K in 2019. At 8 MAP, plots treated with 50% NPK + 50% cow dung gave the highest exchangeable K in 2018 and 2019 respectively. Potassium uptake in the ginger leaf and rhizome were significantly (p<0.05) increased by the treatments. The treatment combination of 50% NPK + 50% rice mill waste gave the highest K uptake at 5 MAP in the two planting seasons and 50% NPK + 50% poultry manure gave the highest K uptake at 8 MAP in the two planting seasons. The fresh leaf biomass at 5 MAP and fresh rhizome yield at 5 and 8 MAP were significantly (p<0.05) increased across all the treatments when compared with the control. At 5 MAP, the highest biomass yields were obtained from the combined treatments of rice mill waste in 2018 and 2019 respectively. The highest yields were obtained at 8 MAP from the combined treatment of poultry manure in 2018 and 2019 respectively. It can therefore be concluded that combination of NPK fertilizer with rice mill waste will give a better yield of ginger if harvested earlier while poultry manure with NPK is a promising amendment for increasing soil chemical properties, nutrient uptake, growth parameters and yield of ginger in Umudike.