Demand-Driven Technologies for Sustainable Maize ... - IITA

198Experimental layout, planting and crop managementFields were cleared at the three locations, ploughed and ridgesspaced 75 cm apart were constructed with a tractor-mounted ridger.The experiment was laid out in split plots in a randomized completeblock design with four replications. The main plots were the three Ptreatments, 0 kg P ha -1 (0P), 30 kg P ha -1 as Triple Superphosphate(TSP), and 90 kg P ha -1 as Rock Phosphate (RP). The RP (36%P 20 5,52%CaO, 0.5%H 20, 0.1%SO 42-; IFDC 1986) was sourced from theRepublic of Togo. The phosphate fertilizers were broadcast on theridges before sowing. The subplots were 13 soybean genotypes(TG×1456–2E, TGm1420, TGm1511, TGm1293, TGm1360,TGm1566, TGm0944, TGm1540, TGm1196, TGm1251, TGm1419,TGm1039, and TGm1576) and one maize genotype (Oba Super 1),all obtained from the germplasm collection of IITA, Ibadan. The plotsize was 4 m × 4 m with six rows plot -1 , a 1 m alley between plots, 1.5m between treatments, and 2 m between replications.Soybean was sown by drilling along the ridges and thinned toobtain an interplant spacing of 5 cm. Maize was sown at four seedshole -1 at 25 cm spacing and thinned to one plant/hole at 2 weeks afterplanting (WAP). The plots were weeded manually using hoes at 3, 5,8, and 10 WAP. Shoot biomass, and vesicular arbuscular mycorrhiza(VAM) colonization of roots, percentage N derived from N 2fi xation(%Ndfa), and total N and P uptake were measured at 50% poddingstage (R 3.5) for soybean (Fehr et al. 1971). The colonization of rootsby VAM was measured using the method of Giovanetti and Mosse(1980) after clearing and staining, following the procedure of Philipsand Hayman (1970). The %Ndfa was measured by determining theconcentrations of ureide-N, amino-N, and NO 3-N in xylem sap, asdescribed by Peoples et al. (1989). The proportion of ureide-N, whichis a refl ection of %Ndfa, was obtained using the following equations:But ureide contains 4N atoms, thus ureide N is calculated as 4×ureidemolar concentration. Therefore,The corresponding values for %Ndfa were then read from tablesprovided by Peoples et al. (1989). Subsequently, the net contribution