Efforts to improve soil productive capacity aimed at boosting crop production in the Northern Ghana has primarily focused on field-based experiments with little documentation on farmer practice and local indigenous knowledge of soil management. A sample group of 114 farmers from five farming communities in the Guinea Savannah was interviewed to evaluate their indigenous knowledge of crop production practices in the context of soil health, fertilization management, and crop yield. Data were collected using semi-structured interviews and responses for each category were calculated using simple proportions. Farmers’ fertilization practice was primarily influenced by fertilization resource availability and crop yield response. The results showed that inorganic fertilization was the commonest fertilization type among farmers. Farmer local indicators of soil health were predominantly limited to visually observable signs such as presence or absence of indicator plants, growth vigor of plants, soil color, and tilth, texture, and compaction. Non-tactile and visible indicators, notably soil chemical composition and presence of soil microorganisms, was rarely used. The listed indicators were congruent with scientific reports, although some knowledge gaps, particularly on the use of indicator plants, were identified. The use of indicator plants as determinants of healthy or non-healthy soils appeared to be influenced by the ease of control of weeds, its utilitarian benefits, benefits to the soil, and threats on cultivated crops. Famers were well informed about the decreasing crop yield. Fertilization practices and limitations in soil management practices with proposed capacity building approaches aimed at enhancing productive capacities of cultivated farmlands are discussed.

There has been increasing attention toward the influence of biofertilizers on the composition of microbial communities associated with crop plants. We investigated the impact of Azospirillum sp. B510, a bacterial strain with nitrogen-fixing ability, on the structure of bacterial and fungal communities within rice plant rhizospheres by amplicon sequencing at two sampling stages (the vegetative and harvest stages of rice). Principal coordinate analysis (PCoA) demonstrated a significant community shift in the bacterial microbiome when the plants were inoculated with B510 at the vegetative stage, which was very similar to the effect of chemical N-fertilizer application. This result suggested that the inoculation with B510 strongly influenced nitrogen uptake by the host plants under low nitrogen conditions. Least discriminant analysis (LDA) showed that the B510 inoculation significantly increased the N₂-fixing Clostridium, Aeromonas and Bacillus populations. In contrast, there was no apparent influence of B510 on the fungal community structure. The putative functional properties of bacteria were identified through PICRUSt2, and this hinted that amino acid, sugar and vitamin production might be related to B510 inoculation. Our results indicate that B510 inoculation influenced the bacterial community structure by recruiting other N₂-fixing bacteria in the absence of nitrogen fertilizer.

Understanding the community composition and diversity of arbuscular mycorrhizal fungi (AMF) in an agricultural ecosystem is important for exploiting their potential in sustainable crop production. In this study, we described the genetic diversity and community structure of indigenous AMF in rain-fed rice cultivars across six different regions in Ghana. The morphological and molecular analyses revealed a total of 15 different AMF genera isolated from rice roots. Rhizophagus and Glomus were observed to be predominant in all regions except the Ashanti region, which was dominated by the genera Scutellospora and Acaulospora. A comparison of AMF diversity among the agroecological zones revealed that Guinea Savannah had the highest diversity. Permutational Multivariate Analysis of Variance (PERMANOVA) analysis indicated that the available phosphorus (AP) in the soil was the principal determining factor for shaping the AMF community structure (p < 0.05). We report, for the first time, AMF diversity and community structure in rice roots and how communities are affected by the chemical properties of soil from different locations in Ghana.

We investigated the root microbiomes of rice sampled from six major rice-producing regions in Ghana using Illumina MiSeq high-throughput amplicon sequencing analysis. The result showed that both bacterial and fungal community compositions were significantly varied across the regions. Bacterial communities were shaped predominantly by biotic factors, including root fungal diversity and abundance. In contrast, fungal communities were influenced by abiotic factors such as soil nitrate, total carbon and soil pH. A negative correlation between the diversity and abundance of root fungi with soil nitrate (NO₃^-) level was observed. It suggested that there were direct and indirect effects of NO₃^- on the root-associated bacterial and fungal community composition. The gradient of soil nitrate from North to South parts of Ghana may influence the composition of rice root microbiome. Bacterial community composition was shaped by fungal diversity and abundance; whereas fungal community composition was shaped by bacterial abundance. It suggested the mutualistic interaction of bacteria and fungi at the community level in the rice root microbiome. Specific bacterial and fungal taxa were detected abundantly in the ‘Northern’ regions of Ghana, which were very low or absent from the samples of other regions. The analysis of indicator species suggested that an ‘ecological specialization’ may have occurred which enabled specific microbial taxa to adapt to the local environment, such as the low-nitrate condition in the Northern regions.

Rice production in Ghana has become unsustainable due to the extremely nutrient-poor soils. It is caused by inadequate soil fertility management, including the inefficient application of fertilizers. A practical solution could be the biofertilizers, Azospirillum sp. B510. We performed field trials in Ghana and Japan to compare the effects of B510 colonization on selected Ghanaian rice varieties grown. The B510 inoculation significantly enhanced the rice cultivars’ growth and yield. The phenotypic characteristics observed in rice varieties Exbaika, Ex-Boako, AgraRice, and Amankwatia were mainly short length and high tillering capacity. These features are attributed to the host plant (cv. Nipponbare), from which the strain B510 was isolated. Furthermore, Azospirillum species has been identified as the dominant colonizing bacterium of rice rhizosphere across a diverse range of agroecologies in all major rice-growing regions in Ghana. Our results suggest that the utilization of B510 as a bio-fertilizer presents a promising way to improve rice growth, enhance soil fertility, and sustain rice productivity in Ghana.

The use of location-specific and underutilized organic residues (OR) as soil amendments in small-holder agro-ecosystems is promising. Six ORs (Leucaena leucocephala, Centrosema pubescens, Gliricidia sepium, Pueraria phaseoloides, Azadirachta indica, and Theobroma cacao) were amended to three tropical soils each at 24 mg g⁻¹ dry soil in 120-day incubation study to estimate their nitrogen (N) mineralization and microbial biomass carbon (C) dynamics. Inorganic N contents varied among ORs, soil type and incubation days. Regardless of soil type, Gliricidia had the highest inorganic N among the studied ORs. Mineralization rate of 1.4 to 1.5 mg N kg⁻¹ soil day⁻¹ was observed for Lego and Tec soils, respectively, and was twice higher than Nya soil. However, Nya soil released higher inorganic N than Tec and Lego soils, implying high N mineralization efficiency in the former. Consistent soil pH increase was respectively observed for Theobroma and Pueraria treatments in all soils. Moreover, Theobroma and Pueraria amendments showed the highest soil microbial biomass C (MBC) at the end of the incubation. The assessed soil properties likely affected by the dominant edaphic factors and management influenced differences in MBC and dissolved organic carbon (DOC) while OR quality indices controlled N mineralization. Thus, we conclude that soil properties and OR type are important factors for optimal utilization of organic resources.