Assessing the impact of organic soil amendments on maize yield and soil health

Thesis Abstract

The persistent reliance on inorganic fertilizers has raised environmental concerns and questioned the sustainability of conventional maize production systems, prompting an urgent need to explore alternative soil fertility management practices. This study aims to assess the impact of organic soil amendments on maize yield and soil health parameters, with the specific objectives of evaluating crop performance, analyzing changes in soil physicochemical properties, and identifying the socio-economic feasibility of organic amendments among smallholder farmers. A mixed-methods research design was employed, combining quantitative field experimentation with qualitative interviews to provide a comprehensive understanding of the subject. The quantitative component involved a randomized complete block design with four treatments—composted manure, poultry litter, vermicompost, and farmyard manure—each replicated three times across a total of 48 plots, with maize variety ZM623 cultivated under typical local agronomic conditions. Data collection instruments included soil sampling kits, crop yield measurement tools, and structured questionnaires administered to 60 smallholder farmers selected via stratified sampling. Soil samples were analyzed for key physicochemical properties such as pH, organic carbon, nitrogen, phosphorus, and cation exchange capacity (CEC) using standard laboratory methods, including spectrophotometry and soil titration. Maize yield was measured at harvest, and data were subjected to analysis of variance (ANOVA) to determine treatment effects, followed by Tukey’s post hoc test for multiple comparisons. The socio-economic data were analyzed through thematic analysis of interview transcripts, providing contextual insights into farmers’ perceptions and adoption likelihood. The expected findings suggest that organic amendments significantly improve soil fertility indicators and maize yields compared to control plots without amendments, with vermicompost and poultry litter exhibiting the highest improvements. Soil analyses are anticipated to show increased organic carbon, nitrogen, and CEC, alongside reduced acidity. The results are expected to demonstrate a positive correlation between soil health parameters and crop productivity, corroborating ecological theories such as the Resource Availability Theory, which posits that enhanced resource levels improve plant growth. The study is projected to contribute novel empirical evidence regarding the efficacy of specific organic amendments in tropical smallholder farming systems, filling existing gaps related to the comparative effectiveness and socioeconomic potential of different organic practices. This research underscores the potential of integrating organic amendments into sustainable maize cultivation strategies, thereby reducing dependency on chemical fertilizers and promoting environmental conservation. The main conclusion will affirm that organic soil amendments are both agronomically and economically beneficial in maize production, providing actionable insights for policymakers, extension agents, and farmers. Recommendations will include advocating for the adoption of composted manure and poultry litter, capacity building on organic practices, and further research into long-term effects and optimization under varying agro-ecological zones. Overall, this study advances the understanding of sustainable soil management practices and offers practical pathways for enhancing maize productivity and soil resilience in smallholder contexts.