Zinc is an important nutrient for plant growth and development. Its availability is influenced by zinc solubilizing microbes (ZSMs). The effects of commonly promoted agronomic practices on the abundance of ZSMs are so far not well understood. In this study, conducted in 2019, we assessed the effects of farmyard manure (FYM) application, either sole or in combination with residue and/or inorganic fertilizer inputs, on ZSM community structure using 11 treatments in a long-term (17 years) integrated soil fertility management experiment located in Western Kenya. Bacterial and fungal community composition were evaluated by amplicon sequencing on an Illumina MiSeq platform. The results showed that putative ZSMs (i.e., the ZSMs generally considered to possess the zinc solubilizing capabilities) were clustered in two major clades based on either the application or no application of FYM. Sole application of FYM significantly (p < 0.05) increased the abundance of several ZSMs under a maize–Tephrosia rotation. In addition, systems with the combined application of FYM with other inputs generally showed significantly increasing trends for some ZSMs under a maize–Tephrosia rotation. Moreover, the combined application of FYM and P rather than only P significantly increased the abundance of some ZSMs under maize monocropping systems. Furthermore, as well as affecting ZSM abundance, soil chemical variables involving soil organic carbon (SOC), total N and Olsen P significantly increased with FYM application. This study indicated that management practices such as the application of FYM that increase SOC, and other soil chemical parameters, also/concomitantly increase ZSM abundance. These results imply enhanced capacities for microbial-linked zinc availability with FYM application.

Introduction: Nitrogen (N) and phosphorus (P) are essential nutrients for plant growth, commonly supplied through costly inorganic amendments. However, despite the benefits of nutrient mineralisation, there is limited quantitative information on its monetary value, and the extent of associated potential financial relief to smallholder farmers, particularly in western Kenya region.Materials and Methods: This study used in situ resin core method to explore the extent of N and P nutrient mineralisation and monetary equivalents under select integrated soil fertility management (ISFM) practices in two long‐term (17 years) trials namely Conservation Tillage (CT1) and Integrated Nutrient Management (INM3).Results: FYM addition increased various soil chemical parameters while sole fertiliser (NPK) reduced soil pH and soil organic carbon (SOC). Phosphorus application was associated with increased P availabillity and its monetary value within the first month (0.29 kg P ha⁻¹; USD 1.13 ha⁻¹) and second month (1.22 kg P ha⁻¹; USD 4.76 ha⁻¹) of incubation. The quantities of N mineralised, and their monetary equivalents varied with fertiliser application and incubation times. Nitrogen fertilisation depressed P mineralisation and monetary benefits. FYM application increased P mineralisation and its monetary value within 30 (0.78 kg ha⁻¹; ~USD 3.02 ha⁻¹) and 60 (1.22 kg ha⁻¹; ~USD 4.76) days of incubation. Residue application increased mineralised N (17.48 kg ha⁻¹; ~USD 22.79 ha⁻¹) after 60 days. Maize and soybean intercropping increased N mineralisation (45.81 kg N ha⁻¹) and monetary value (USD 59.76 ha⁻¹). SOC and other soil variables, their stoichiometry ratios and N mineralisation were significantly correlated. Combined NPK and FYM application significantly (p ≤ 0.05) increased maize yields and grain prices.Conclusion: These findings reflect potential nutrient‐based economic advantages of ISFM practices to resource‐limited smallholder farmers. Combined application of NPK fertiliser and FYM is integral in not only optimising crop yields, but also driving key soil health‐related parameters and economic benefits.

Introduction: Soil bacterial community structure, abundance and diversity, important in biogeochemical cycling, are influenced by several anthropogenic and edaphic factors. Numerous agronomic practices have been promoted to improve soil fertility and crop production in western Kenya, but little is known on their impacts on soil microbial diversity in the region.Materials and Methods: In this study, conducted in 2019, we assessed the influence of various long‐term (17 years) agronomic management practices, involving application of farmyard manure (FYM) either sole or under different combinations with inorganic nitrogen (N), phosphorus (P) and potassium (K), using 12 treatments, on bacterial community composition, relative abundance and diversity. The bacterial community composition was assessed through amplicon sequencing on an Illumina Miseq platform conducted in MR DNA Laboratory, USA.Results: The soil bacterial community composition and diversity were predominantly higher under management practices with application of FYM, either sole or in combination with inorganic fertilisers compared to treatments with either sole NPK fertiliser or no input application. Certain bacterial taxa, involving Proteobacteria, Bacteroidetes, Nitrospirae, Fusobacteria, Nitrospinae and Actinobacteria predominated in management practices where FYM was added either solely or in combination with chemical fertilisers. In addition, several soil chemical parameters showed significant influences on bacterial composition, relative abundance and diversity indices. Soil pH, soil organic carbon (SOC), N, K, Ca, Mg, Cu, Zn, Fe and cation exchange capacity consistently showed strong positive correlation with numerous bacterial phyla. Bacterial phyla were significantly affected by treatments. Some bacterial phyla, like Chloroflexi and Acidobacteria, were mostly dominant in treatments applied with organic inputs but were depressed under carbon‐deficient treatments (no‐input control and sole NPK application treatments).Conclusion: This study revealed that long‐term agricultural management practices that seek to improve SOC content and nutrient availability also stimulated bacterial diversity and shifted bacterial composition.

Zinc is an important nutrient for plant growth and development. Its availability is influenced by zinc solubilizing microbes (ZSM). Effects of commonly promoted agronomic practices on the abundance of ZSM are so far not well understood. In this study, we assessed the effects of farmyard manure (FYM) application, either sole, or in combination with residue and/or inorganic fertilizer inputs on ZSM community structure using 11 treatments in a long-term (17 years) integrated soil fertility management experiment located in western Kenya, The study was conducted in 2019. Bacterial and fungal community composition (at 0-15 cm depth) was evaluated by amplicon sequencing on an Illumina Miseq platform following the manufacturer’s guidelines. Microbial diversity indices (Shannon, Simpson and Chao1) and statistical analyses were computed using R project packages. Putative ZSM (i.e., the ZSM generally considered to possess the zinc solubilizing capabilities) were clustered in two major clades based on either application or no application of FYM. Sole application of FYM significantly (P<0.05) increased the abundance of several ZSM under maize-tephrosia rotation. In addition, systems with combined application of FYM with other inputs generally showed significantly increasing trends for some ZSM under maize-tephrosia rotation. Moreover, combined application of FYM and P rather than P only significantly increased abundance of some ZSM under maize-monocropping systems. Furthermore, besides affecting ZSM abundance, soil chemical variables involving soil organic carbon (SOC), total N and Olsen P significantly increased with FYM application. This study indicated that management practices like application of FYM that increase SOC, and other soil chemical parameters, also/concomitantly increase ZSM abundance; implying enhanced capacities for microbial-linked zinc availability.

In sub‐Saharan Africa, there is growing interest in conservation agriculture practices, including reduced tillage (e.g., ripping), residue retention, and crop diversification, but their effects on soil moisture and penetration resistance in sub‐humid regions remain unclear. This study investigated the effect of ripping, residue retention, cropping systems, and fertilizer management on soil moisture, penetration resistance, and maize ( Zea mays L.) grain yield in a sub‐humid zone of western Kenya. The study was conducted in a long‐term experiment in western Kenya, using a split‐split‐split plot design with tillage in the main plot, while residue retention, cropping systems, and fertilizer application were the sub‐plots, sub‐sub‐plots, and sub‐sub‐sub‐plots, respectively. There were nine treatments and four replications. Soil moisture, penetration resistance, and maize grain yield were measured between 2023 and 2024. Residue retention resulted in significantly ( p  < 0.001) higher soil moisture (52.93–55.09 mm) in the 0‐ to 90‐cm soil depth than residue removal (25.98–28.91 mm). Maize–soybean rotation also had significantly higher ( p  < 0.001) soil moisture in the 0‐ to 90‐cm soil depth (41.42–45.08 mm) than the continuous maize (36.29–41.07 mm). The penetration resistance in the wet period ranged between 90 and 320 pounds per square inch (PSI), and between 200 and 492 PSI during the dry period. Ripping resulted in 12% higher maize grain yields than hand digging. Maize–soybean rotation had a higher ( p  < 0.001) maize grain yield (3.93 t/ha) than continuous maize system (1.57 t/ha). Nitrogen application at 90 kg N/ha in a continuous maize and 60 kg N/ha in maize–soybean rotation systems resulted in 118% and 85% higher maize grain yield, respectively, than when no nitrogen was applied. Similarly, applying phosphorous (60 kg P/ha) and potassium (60 kg K/ha) in maize–soybean rotation increased maize grain yield by 40% more than when potassium (60 kg K/ha) was applied as the only nutrient. Therefore, residue retention and ripping significantly improve soil health by enhancing moisture retention and reducing penetration resistance. Farmers in the sub‐humid western Kenya region can increase maize yields by adopting maize–soybean rotation, applying appropriate fertilizers (nitrogen, phosphorous, and potassium, each nutrient applied at the rate of 60 kg/ha), and implementing residue retention and ripping, especially under low rainfall conditions.

Zinc is an important nutrient for plant growth and development. Its availability is influenced by zinc solubilizing microbes (ZSM). Effects of commonly promoted agronomic practices on the abundance of ZSM are so far not well understood. In this study, we assessed the effects of farmyard manure (FYM) application, either sole, or in combination with residue and/or inorganic fertilizer inputs on ZSM community structure using 11 treatments in a long-term (17 years) integrated soil fertility management experiment located in western Kenya, The study was conducted in 2019. Bacterial and fungal community composition (at 0-15 cm depth) was evaluated by amplicon sequencing on an Illumina Miseq platform following the manufacturer’s guidelines. Microbial diversity indices (Shannon, Simpson and Chao1) and statistical analyses were computed using R project packages. Putative ZSM (i.e., the ZSM generally considered to possess the zinc solubilizing capabilities) were clustered in two major clades based on either application or no application of FYM. Sole application of FYM significantly (P<0.05) increased the abundance of several ZSM under maize-tephrosia rotation. In addition, systems with combined application of FYM with other inputs generally showed significantly increasing trends for some ZSM under maize-tephrosia rotation. Moreover, combined application of FYM and P rather than P only significantly increased abundance of some ZSM under maize-monocropping systems. Furthermore, besides affecting ZSM abundance, soil chemical variables involving soil organic carbon (SOC), total N and Olsen P significantly increased with FYM application. This study indicated that management practices like application of FYM that increase SOC, and other soil chemical parameters, also/concomitantly increase ZSM abundance; implying enhanced capacities for microbial-linked zinc availability.