Effects of Varying Tillage Passes and 15-15-15 NPK Fertilizer on SomeAgronomic Parameters, Nitrogen, Phosphorous and Potassium Uptake byAmaranthus viridis in Derived Savannah of Southwest Nigeria

Experiment was conducted to obtain information on seperate and interaction effects of tillage passes and 15-15-15 NPK fertilizer application rates on some growth parameters, N, P and K uptake by Amaranthus viridis, hence the use of a tractor implement with specified specification on sandy clay soil planted with Amaranthus viridis. The research was conducted at vegetable research plot, Department of Agricultural Technology, The Oke-Ogun Polytechnic, Saki, between 2nd July and 30th September, 2015. Soil treatments consisting of three levels of tillage passes (0, 3 and 6) equivalent to 1.7, 1.3 and 1.5 g/cm3 soil bulk density respectively, four levels of 15-15-15 NPK fertilizer rates (0, 100, 150 and 200 kg/ha) and replicated three times in a completely randomized design. The results showed that no-tillage pass had significant effect on bulk density, zero tillage reduced the percent uptake of N(0.58-0.46), P (0.002-0.0005) and K (0.13-0.04), however, statistically, the reduced effects were more pronounced on Nitrogen and Potassium. Fertilizer rates significantly improved percent uptake of N (0.11-0.58), P (0.0004-0.005) and K (0.04-0.07). Interactions (tillage passes × fertilizer rates) effects were observed on plant height, stem girth,fresh weight, root length and percent N, P and K uptake, but T2F2 (6 passes × 150 kg/ha) significantly increasedplant height and improved uptake of Phosphorous, therefore, 6 passes and 150 kg/ha 15-15-15 could be more suitable for optimum production for Amaranthus viridis on a sandy clay soil.