Low fertility and inefficient management of sub-Saharan African soils have been the major challenges facing productivity among smallholder farmers. Unfortunately, inorganic fertiliser used as major soil nutrient management is unsustainable, causing soil degradation and environmental pollution. Therefore, smallholder farmers may only realise their maximum potential if a more sustainable, low-cost and efficient integrated nutrient management system compatible with their socioeconomic status is practised. Currently, the increasing demand for sustainable agriculture is driving the use of biological fertilisers, which are composed of beneficial microorganisms; ranging from bacteria to blue-green algae and fungi. Biofertilisers such as Rhizobium, Azotobacter, Azospirillum, Pseudomonas and Bacillus have invaluable use in sustainable agriculture owing to their environmentally-friendliness, cost-effectiveness and improved productivity benefits. They improve plant nutrition and yield through biological nitrogen fixation, nutrient solubilisation, biocontrol activities and production of plant growth promoting substances. This review specifically focuses on biofertiliser potential as an efficient integrated nutrient management in increasing smallholder farmer productivity and profitability. It also suggests that increasing biofertiliser awareness and use is an impetus for maintaining and improving ecological stability and alleviating poverty, especially among the rural dwellers. Importantly, efficient biofertiliser strategies by stakeholders will improve adoption of this technology among smallholder farmers. Subjects: Soil science; Microbiology; Biotechnology; Agricultural science

Anaerobic digestion (AD) for biogas production is affected by many factors that includes organic loading rate (OLR). This OLR appears to be closely linked to various other factors and understanding these linkages would therefore allow the sole use of OLR for process performance monitoring, control, as well as reactor design. This review’s objective is to collate the various AD factor specific studies, then relate these factors’ role in OLR fluctuations. By further analyzing the influence of OLR on the AD performance, it would then be possible, once all the other factors have been determined and fixed, to manage an AD plant by monitoring and controlling OLR only. Decisions on reactor design, process kinetics, biogas yield and process stability can then be made much more quickly and with minimal troubleshooting steps.