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

146Table 4. Rotation† and fertilizer effects on organic carbon of 0-15 cm ofa Typic Haplustalf.RotationMS1 MS2 MF MM MeanFertilizer (kg N ha -1 ) ----------------Organic carbon, g kg -1 ---------------0 5.8 5.7 5.4 5.0 5.590 7.1 7.2 5.9 5.9 6.5Mean 6.5 6.5 5.7 5.4LSD (0.01)Rotation (R) 0.06Fertilizer (F) 0.06R x F 0.12† MS1 = TGx 1448-2E-Maize; MS2 = Samsoy-2-Maize; MF = Fallow-Maize;MM = Continuous maize.Table 5. Rotation† and fertilizer effects on total nitrogen of 0-15 cm of aTypic Haplustalf.RotationMS1 MS2 MF MM MeanFertilizer (kg N ha -1 ) ---------------------Total N, g kg -1 ------------------0 0.85 0.87 0.80 0.74 0.8290 1.08 1.15 1.06 0.88 1.04Mean 0.97 1.05 0.93 0.81LSD (0.01)Rotation (R) 0.37Fertilizer (F) 0.27R x F 0.53† MS1 = TGx 1448-2E-Maize; MS2 = Samsoy-2-Maize; MF = Fallow-Maize;MM = Continuous maize.and Johnston (1986) reported improvement in organic matter dueto the inclusion of legumes in a cropping system. However, Lal et al.(1994) observed that tillage practices also infl uence soil OC contentsin legume-based rotations.Total Nitrogen. The effect of soybean rotation on residual soil N is welldocumented. Fallow-based rotations have also been found to improvesoil total N (Juo and Lal 1977). Expectedly, soil total N followed asignifi cantly similar trend to that of OC. The mean total N of the surfacesoil (0-15cm) was 0.97 g kg -1 in MS1 and 1.01 g kg -1 in MS2 morethan 0.93 g kg -1 in MF and 0.81 g kg -1 in MM (Table 5). There wasno signifi cant difference between MS1, MS2, and MF but the MMtreatment was signifi cantly lower than MS1 and MS2. Apparently,N 2-fi xation by grain legumes and the presence of residue mulch onfallow plots increased soil total N. Using the bulk density of 1.4 kgdm -3 commonly reported in the NGSN (Adeoye 1986; Adeoye andMohammed-Saleem 1990) and the weight of a hectare furrow slice of