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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.

Information on long-term fertilization combined with crop rotation can contribute to better management of West African Lixisols. There is little information on how long-term organic inputs influence soil chemical properties under cereal monoculture versus a rotation with a legume. Here, we investigated how fertilization regimes with emphasis on organic inputs influence soil chemical properties in sorghum monoculture compared to sorghum-cowpea rotation. The long-term field trial of Saria in Burkina Faso, which has been in operation since 1960, was used for this purpose. Soils were sampled at the 0-20 cm depth to determine their organic C, total N, total P, mineral N, available P, pHwater, exchangeable basic cations, and cation exchange capacity. The best soil properties were exhibited with the application of 40 t ha-1 of manure. Recycling of sorghum residues combined with mineral fertilization led to a decrease in mineral N and available P but maintained a higher level of total N and P compared to exclusive mineral fertilization. Organic inputs determined soil properties and sorghum yield better (R2 = 0.89) in rotation than in monoculture. Our results show that a better productivity of the studied Lixisol requires an application of manure at more than 5 t ha-1 combined with mineral fertilization. In addition, a rotation including a legume and a regular recycling of crop residues is necessary.

Low phosphorus availability in cultivated soils limits sustainable crop production in sub‐Saharan Africa. This study aimed at evaluating the effect of long‐term application of different types of organic amendments on soil P forms, P use efficiency and sorghum yields. A long term experiment established in 1980 at Saria in Burkina Faso, comparing the effects of manure, compost and sorghum straw was used. Manure and compost significantly increased organic P and resin‐P by about 35% and 64%, respectively after 10 and 32 years of sorghum cultivation, and HCl‐P after 32 years of cultivation compared to the control. Manure significantly increased NaHCO3-Pi and NaOH-Pi by 63% and 26%, respectively compared to the control. Sorghum straw had little effect on measured soil P forms. Manure and compost were the best in increasing sorghum grain yield, which effect were strongly correlated to soil pH, carbon and nitrogen. The partial factors productivities of P resulting from the application of studied organic a...

Increasing soil phosphorus and organic matter content for crop production while reducing the cost of production are required to facilitate the achievement of green revolution in Africa. Field and p...