Comparative effects of organic compost and NPK fertilizer on soil fertility, yield and quality of amaranth in southwest Nigeria

The need for an increased production of vegetables to meet the dietary vitamin requirements of the people had necessitated a research in the use of manure in improving the soil fertility for an improved yield andquality of amaranth. The research was conducted in Obasoto Farm (latitude 7°10’N and longitude 5°37’E) in Owo Local Government Area of Ondo State, Nigeria in the early and late seasons of 2007, 2008 and 2009. Theexperimental design was a randomized complete block with three treatments replicated three times. The three treatments were 0 kg/ha manure, 2t/ha organic compost and 200 kg/ha NPK 15-15-15. Amaranthus cruentus seeds obtained from the Ondo State Agricultural Development Project were raised in the nursery and transplanted at a spacing of 10 x 20 cm into 1 x 3 meter manually prepared beds. Each manure type wasincorporated by ploughing it in while preparing the bed at 600 g organic compost and 60 g NPK 15-15-15 fertilizer per the 1 x 3 meter bed respectively. Pre-treatment and post planting soil samples were taken forlaboratory soil analysis of soil chemical properties for a comparison of the assessment of the cumulative effects of organic compost and inorganic fertilizer in improving soil fertility over a period of three years. The organicmatter increased by 23.3% and 0.6% in the second and third year respectively in the plot treated with organic compost, while there was no such increase trend in the plot treated with 200 kg NPK/ha. The organic matter content correlated positively with the yield and vitamin C content of amaranth