Long-Term Organic Inputs Determine Soil Productivity Better in Sorghum-Cowpea Rotation Than in Sorghum Monoculture

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.