Evaluating Sustainable Fertilizer Practices on Maize Yield and Soil Health

Thesis Abstract

The over-reliance on conventional chemical fertilizers in maize production often leads to significant soil degradation and diminished crop yields, posing a challenge to sustainable agriculture and food security. This study aims to evaluate the effects of sustainable fertilizer practices on maize yield and soil health, with specific objectives to assess the impact of integrated nutrient management techniques, quantify changes in soil physicochemical and biological properties, and determine the economic viability of adopting sustainable fertilizer regimes among smallholder maize farmers. To accomplish these objectives, a field-based empirical investigation was conducted in a maize-growing region characterized by intensive chemical fertilizer use. The research adopted a randomized complete block design (RCBD) consisting of four treatment groups conventional chemical fertilizer application, organic fertilizer exclusively, combined organic and inorganic fertilizer application, and a control with no fertilizer. A total of 120 smallholder farmers’ fields were sampled, with 30 replicates per treatment, selected through stratified random sampling to ensure representative coverage across soil types and farm sizes. Data collection involved soil sampling at the beginning and end of the cropping season, with laboratory analyses utilizing standard procedures such as pH measurement, soil organic carbon determination via Walkley-Black method, microbial biomass estimation through chloroform fumigation, and nutrient analysis using ICP-OES. Maize yield data were recorded at harvest, and economic assessments employed cost-benefit analysis to evaluate profitability. The validity and reliability of measurements were ensured through calibration of laboratory equipment and repeated sampling, with data quality checked via control samples. Statistical analysis included analysis of variance (ANOVA) for comparing treatment effects on yield and soil parameters, followed by post hoc tests; multiple regression analysis to determine relationships between soil health indicators and maize productivity; and economic analysis for cost-effectiveness. Additionally, the study applied the Theory of Planned Behavior to understand farmers' adoption intentions and used structural equation modeling (SEM) to elucidate the pathways linking fertilizer practices to soil health and yield outcomes. Expected findings suggest that integrated organic and inorganic fertilizer use significantly enhances maize yields by improving soil organic matter, microbial activity, and nutrient availability, compared to conventional and no-fertilizer treatments. Organic-only practices are anticipated to improve soil biological health but with modest yield increases, while reliance solely on chemical fertilizers may lead to soil acidification and reduced biological activity over time. Economically, the combined approach is projected to be more profitable, offering incentives for wider adoption. These results will contribute to the body of knowledge on sustainable nutrient management, providing empirical evidence that supports policy formulation and extension services aimed at promoting environmentally sustainable maize production systems. The study concludes that adopting integrated fertilizer practices can enhance maize productivity while maintaining or improving soil health, thereby supporting sustainable agricultural intensification. Recommendations include promoting the adoption of combined organic and inorganic fertilizers through farmer education programs and policy incentives, emphasizing the importance of soil health as a foundation for long-term productivity. Furthermore, the research suggests that future studies should explore long-term impacts over several cropping seasons and examine the social and behavioral factors influencing adoption rates among diverse farming communities.