The decline in soil productivity amidst efforts to increase crop yield in Sub Saharan Africa (SSA) has made it imperative to assess the current fertilization management approaches. This study was conducted in two agroecological zones (i.e., Guinea Savannah (GS) and Deciduous forest (DF)) of Ghana to evaluate how different fertilization schemes in the long term (>5 years) impacted the soil biochemical properties. Soil samples under four fertilization schemes (inorganic fertilizer only, low-to-medium organic residues only, inorganic fertilizers plus low-to-medium organic residues, and no fertilization) from 20 farmers’ field were sampled from March to April 2015. Soil biochemical quality indicators were determined using standard procedures. Overall, the average chemical and microbial biomass contents for most indicators were significantly higher in DF compared to GS. Relative to the reference sites, soil quality improvement were observed under inorganic fertilization in both agroecologies in contrast to significant soil deterioration (26.5%) under sole organic residue application in GS. Furthermore, the results showed that increased inorganic fertilization rate alone or combination with organic residues improved soil quality relative to the reference. The present results suggest the need to raise the current fertilizer application rates, especially in GS in order to enhance optimum soil productivity. Full article

The problems of low soil fertility resulting from continuous monocropping, crop residue removal and limited fertilizer use represent key challenges to produce surplus food for the ever increasing population of Ethiopia. However, the practices of crop rotation and integrated sources of fertilizer uses could potentially improve soil fertility and productivity. In 2012 and 2014, soybean with different trials consisting of two soybean varieties (Boshe and Ethio-ugozilavia), three levels of farm yard manure (FYM) (3, 6 and 9 t/ha) and three phosphorus levels (8, 16 and 24 kg P ha−1) were combinedin2×3×3factorialarrangements. Twosoybeanvarietiesreceivingnofertilizerapplication followed by finger millet receiving a recommended rate (20 kg P/ha) were included. The experiment was laid out in a randomized complete block design with three replications. In 2013 and 2015, finger millet was planted on each soybean plot as per previous treatment arrangements to evaluate the effect of the precursor crop (soybean) and integrated fertilizer application on yield performance of the subsequent finger millet. Soil pH, organic carbon, total nitrogen and available phosphorus before planting and after crop harvest of soybean in each year showed treatment differences. Both precursor crop and fertilizer application had a positive effect on soil fertility status and, hence, improved the performance of the subsequent finger millet. On the other hand, since the rainfall amount and distribution were different in the 2012 and 2014 seasons, the response of soybean varieties to applied fertilizers was significantly affected, and the correlation between soybean yield and annual rainfall was strongly positive. Use of an early maturing soybean variety (Boshe) with the lowest rates of organicandinorganicfertilizersgavesignificantlyhigheryieldin2012(shortrainyseason)compared with other treatment combinations. In the 2014 cropping season, however, ‘Ethio-ugozilavia’ showed greateryield performancewith the combinedapplication of3 t FYM/haand 1616kg PP/ha followed by 3 t FYM and 88 kg P/ha. Hence, it is recommended to use the ‘Boshe’ variety under a short rainy season and under a low soil fertility status, while variety the ‘Ethio-ugozilavia’ can be used under goodrainyandsoilfertilitymanagementconditions. Consideringresidualeffects,theuseoftheearly maturing soybean variety as a precursor with 3 t FYM/ha and 8–16,816 kg P/ha during the short rainy season could enhance the yield of the subsequent finger millet. On the other hand, the use of the late maturing soybean variety as a precursor with higher organic fertilizer rates (6–9 t FYM/ha) resulted in a significant yield increase of the subsequent finger millet. The use of a late maturing variety of soybean with lower rates of organic manure resulted in a finger millet yield comparable to farmers’ practice, indicating that this option can be adopted by smallholder farmers who cannot produce sufficient organic manure. This study showed that planting of finger millet after a soybean precursor crop even without fertilizer application could give better yield and economic benefits as it saves 70–85% of chemical fertilizer costs compared to the farmers’ practice. Full article

Arbuscular mycorrhizal fungi (AMF) play major roles in nutrient acquisition by crops and are key actors of agroecosystems productivity. However, agricultural practices can have deleterious effects on plant–fungi symbiosis establishment in soils, thus inhibiting its potential benefits on plant growth and development. Therefore, we have studied the impact of different soil management techniques, including conventional moldboard ploughing and no-till under an optimal nitrogen (N) fertilization regime and in the absence of N fertilization, on AMF spore density and soil chemical, physical, and biological indicators in the top 20 cm of the soil horizon. A field experiment conducted over six years revealed that AMF spore density was significantly lower under conventional tillage (CT) combined with intensive synthetic N fertilization. Under no-till (NT) conditions, the density of AMF spore was at least two-fold higher, even under intensive N fertilization conditions. We also observed that there were positive correlations between spore density, soil dehydrogenase enzyme activity, and soil penetration resistance and negative correlations with soil phosphorus and mineral N contents. Therefore, soil dehydrogenase activity and soil penetration resistance can be considered as good indicators of soil quality in agrosystems. Furthermore, the high nitrate content of ploughed soils appears to be detrimental both for the dehydrogenase enzyme activity and the production of AMF spores. It can be concluded that no-till, by preventing soil from structural and chemical disturbances, is a farming system that preserves the entire fungal life cycle and as such the production of viable spores of AMF, even under intensive N fertilization. Full article