This study reports the effectiveness of some selected rhizobium strains in enhancing nitrogen fixation and nutrient uptake in Vicia faba L. Multi-location field experiments were conducted for two years (2016 and 2017) using a split-plot in randomized complete block design. Treatments comprised six rhizobium strains as the main plot factor and three varieties of Vicia faba as the sub-plot factor. Non-inoculated plants with or without N fertilizer served as +N and −N controls, respectively. Peat carrier-based inoculant of each strain was applied at the rate of 10 g kg⁻¹ seed. Data on nodulation were taken at the late-flowering stage, whereas nitrogen and phosphorus concentrations in plant parts were analyzed at physiological maturity. The total nitrogen difference method was employed to quantify nitrogen fixation. Location x rhizobium strain x variety interaction had a significant effect on nodule dry weight plant⁻¹. Rhizobium strains significantly enhanced nodulation, nitrogen fixation, nutrient uptake and soil nitrogen balance. Inoculation with NSFBR-12 and NSFBR-15 resulted in the highest nitrogen fixed, nutrient uptake and soil nitrogen balance. Vicia faba inoculated with the two top performing strains, NSFBR-12 and NSFBR-15 fixed respectively 87.7% and 85.5% of the total nitrogen uptake. Non-inoculated plants fulfilled proportionately more of the total nitrogen uptake through nitrogen derived from the soil rather than fixed nitrogen. Soil available phosphorus and pH had appreciable influences on nitrogen and phosphorus uptake of inoculated Vicia faba. Inoculation with competitive and effective rhizobium strains can improve soil nitrogen balance, nitrogen fixation and nutrient uptake of Vicia faba.

• Inoculation increased grain yield over the control by 24%. • Combined application of P + I increased grain yield over the control by 37%. • Soil and environmental factors explained up to 79% of yield variation. • Agronomic index for responsiveness was robust than economic index. • About 53% of the farmers that applied inoculant had VCR of ≥2.

A two-year field experiment was conducted in Niger to explore the effects of integrated use of millet glume-derived compost (MGD-Compost) and NP fertilizer on soil microbial biomass carbon (C_mic), nitrogen (N_mic) and millet yields. Three compost rates (3000 kg ha⁻¹, 1500 kg ha⁻¹ and 0 kg ha⁻¹) and three NP fertilizer rates (100%, 50% and 0% of recommended NP fertilizer) were arranged in a factorial experiment organized in a randomized complete block design with three replications. Combined application of compost and NP fertilizer induced a synergistic effect on C_mic and N_mic. Compost application increased millet grain yield from 59% to 91% compared to control. Combined application of compost and NP fertilizer increased millet grain yields from 57% to 70% in 2013 and from 36% to 82% in 2014 compared to sole application of mineral fertilizer. Agronomic efficiency (AE) of nitrogen values increased by 3.7 and 2.3 times than those of sole NP fertilizer application in 2013 and 2014, respectively. Phosphorus AE was 1.6 times higher than that of the sole application of NP fertilizer. These findings indicate that integrated application of MGD-Compost and NP fertilizer enhances soil microbial biomass content and increases millet grain yield in low-input cropping system.

The use of cow dung as a source of plant nutrients is widespread among many smallholder farmers in Ghana. The benefits of cow dung application in crop production depend on the amount, quality, nutrient-release patterns, and uptake by crops. Samples of cow dung from three main systems of manure management (free range, semi-intensive, and intensive) were collected from the Kumasi Metropolis in the semideciduous forest zone of Ghana and analyzed for nitrogen (N), carbon (C), phosphorus (P), potassium (K), calcium (Ca), magnesium, (Mg), and ash contents. This research was undertaken to corroborate results of an earlier study in the interior savanna zone of Ghana, because manure quality is a function of its management (handling, storage, and transport), animal breed, and vegetation type (feed). Nitrogen content varied from 1.44 to 2.10% with the intensive system of management recording the greatest value. Phosphorus varied from 0.48% under free-range (field) system to 0.80% under the intensive system. The greatest and lowest total K values of 1.74% and 1.11% were respectively recorded under the intensive and free-range management systems. Generally, the study indicated there was relatively better manure quality under the intensive system than in the semi-intensive and free-range (field) systems. The cow dung collected under the various manure-management systems was then incubated in a laboratory study to assess their nutrient-release patterns. The results revealed that the manure under the intensive system mineralized ammonium N during the first 6 weeks of incubation with peak mineralization in the fourth week. Immobilization of nitrate N was observed from the second to the eighth week of incubation from cow dung under all the management systems. Total N [nitrate (NO₃⁻) + ammonium (NH₄⁺)] was immobilized under the free-range and semi-intensive management systems throughout the incubation period except in the first week. Peak net N mineralization was observed during the fourth week of incubation from cow dung under the intensive system of manure management. Results of the study suggested that total mineral N needs of crops might not be met entirely through application of cow dung to Ferric Acrisol due to immobilization during appreciable period of decomposition of the manure.