Influence of N Starter Dose on Yield and N-uptake of two Soyabean varieties in Southern Guinea Savanna of Nigeria, West Africa
1Oyatokun Olukayode Stephen, 2Adeoye Gideon Olajire and 3Oluwasemire Kolapo Olatunji
1,2 & 3Department of Agronomy, University of Ibadan
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Accepted on June 30, 2013
Nitrogen is one of the major nutrient elements of soyabean and is the most-limiting factor for its production after moisture in sub-sahara Africa. Its source could be organic or inorganic. Two parallel field experiments were conducted during 2010 planting season to evaluate the influence of Nitrogen (N) starter dose on two soyabean varieties in southern guinea savanna agro-ecology zone of Nigeria. The objectives were to assess N dose that synergies yield across the two varieties and to evaluate N-assimilation of the two varieties under varying N starter dose. The experiments were set up in a 5x2x3 split-plot fitted into randomized complete block design, where N doses of 0 (control), 5, 15, 25 and 35 kg N/ha applied in the form of urea a week after planting were at the main plot and soyabean varieties: TGx1485-1D and TGx1448-2E were at the sub-plot with three replications. All plants located in a well surrounded pre-selected final harvest area of 750cm²/subplot were selected at maturity for the evaluation of biomass yield. The pods were threshed and grains dried to determine 100 seed weight, seed yield and harvest index. There was a significant difference (p<0.05) in varietal response to some traits measured. While TGx1448-2E produced a significantly higher 100 seed weight of 27.28g, TGx1485-1D produced 100 seed weight of 21.73g. Also TGx1448-2E had a significantly higher plant dry biomass (7.363t/ha) than TGx1485-1D (4.673t/ha) and these could be due to genotypic superiority of TGx1448-2E to TGx1485-1D. However, the application of N starter-dose was found to have less effect on the yield and N-uptake of soyabean within individual varieties investigated in the region. This was attributed to high rainfall regime during the growing season which might have led to leaching-loss of the applied N. This is a merit for organic agriculture which excludes environmental pollution that the mineral fertilizer caused in this investigation.