Microbial Properties of a Ferric Lixisol as Affected by Long Term Crop Management and Fertilization Regimes in Burkina Faso, West Africa

We used an ongoing long-term field trial established since 1960 in Burkina Faso, to study the microbial properties of a Ferric Lixisol under various crop management and fertilization regimes. Microbial respiration rate, microbial biomass carbon (MBC) and soil bacteria’s number were assessed in soil samples taken at 0 - 20 cm depth. The crop management were continuous cropping of sorghum (Sorghum bicolor L.) (S/S) and rotation between sorghum and cowpea (Vigna unguiculata L.) (S/C), while the fertilization regimes were: 1) Control (te); 2) Low rate of mineral fertilizer (fm); 3) Low rate of mineral fertilizer + sorghum straw restitution (fmr); 4) Low rate of mineral fertilizer + low rate of manure (fmo); 5) High rate of mineral fertilizer (FM); and vii) High rate of mineral fertilizer + high rate of manure (FMO). The manure is applied every second year. The results indicate that sorghum/cowpea rotation significantly increase MBC and bacteria number as compared to continuous sorghum cropping. MBC ranged from 335.5 to 54.85 μg C g−1 soil with S/S and from 457.5 to 86.6 μg C g−1 soil with S/C. Application of high level of manure and mineral fertilizer increase microbial respiration rate and MBC. The highest MBC was observed with FMO and the lowest with the control. In general, the metabolic quotient (qCO2) was negatively impacted by the fertilization and cowpea rotation. For S/S rotation, qCO2 of the control was 1.5 to 2 times that of the treatments with low mineral fertilizer (fmr, fmo and fm) and 3 times that of the high rate of fertilization (FM and FMO). With S/C rotation, qCO2 of the control was 2 times of that fmr, FM and FMO and 0.8 times that of fmo and fm. Soil bacteria in the fmr were 63.6 and 12.4 times the control in the S/S and S/C rotations, respectively. In sum, combined application of manure and mineral fertilizer with crop rotation is the best management practices to improve in sustainable way microbial activities in tropical soil.