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

160was applied about 5 cm deep, made along the ridge, 5–10 cm awayfrom the plants. The remaining two-thirds of the fertilizer was appliedafter weeding 5–6 WAP. In both cases, fertilizer application was by bysingle band placement followed by incorporation into the soil. Weedswere controlled using the West African hoe when necessary. All plotswere remoulded manually with the hoe at 8 WAP to control weeds.Sampling and analysisSurface soil (0-15 cm) samples were collected with an auger beforecommencement of the study, after harvest in 2001 and beforeland preparation in 2002. Air-dried 2 mm-sieved soil was used foranalysis. Particle size distribution was determined by the Bouyoucoshydrometer method (Klute 1986). Soil reaction was determinedpotentiometrically in 1:2.5 soil to water ratio with the glass electrodepH meter. The Walkley and Black wet oxidation method was usedto determine the organic carbon (C) content (Nelson and Sommers1982). Exchangeable bases were determined by extraction withneutral 1N NH 4OAc. Potassium (K) in the extract was determinedwith fl ame photometer while calcium (Ca) and magnesium (Mg)were determined using the atomic absorption spectrophotometer(Kundsen et al. 1982). Available P was extracted by Bray P1 method.The P concentration in the extract was determined colorimetricallyusing the spectromic 70 spectrophotometer. Total and inorganic Nwere determined by the micro-Kjeldahl digestion procedure (Bremner1982; Bremner and Mulvaney 1982).Maize grain yield analysis was determined by harvesting maizeears in the three central rows leaving out border plants at both ends(net plot of 8.7 m 2 ). These were shelled, air-dried and weighed. Thegrain yield was adjusted to 12 % moisture content for each plot.The NFRV of the legumes was estimated by the method describedby Carsky et al. (2001). The response of maize to urea N in the fallowplot was fi tted to a linear model. The intercept is the grain yield afterfallow with no N fertilizer and the slope is the response of maize tofertilizer N.Yield after legume with no N fertilizer – InterceptNFRV =SlopeThe General Linear Model Procedure of SAS (SAS Inst. 1999) wasused for statistical analysis of the data, including analysis of variance(ANOVA) and means separation by Student-Neuman Keuls test. Pairedt-tests were also used to compare means of the chemical propertiesbefore and after treatments.