Comparative Assessment of Soil Fertility Across Urban and Rural Farms

Thesis Abstract

Urban and rural farming systems increasingly diverge in soil management and fertility dynamics, posing risks to productivity and food security in peri-urban landscapes. This study addresses the gap in comparative understanding of soil fertility status across contrasting farm settings by examining how management practices, soil properties, and environmental factors interact to shape fertility indicators. The aim is to assess and compare soil fertility across urban and rural farms and to identify the primary drivers of fertility disparities. Specific objectives include (1) characterizing physical, chemical, and biological soil properties (texture, pH, organic carbon, total N, available P, cation exchange capacity, microbial biomass, and enzyme activities) in 60 urban and 60 rural farm plots; (2) evaluating the influence of farm management practices (fertilizer type and rate, organic amendments, irrigation, tillage, and crop rotation) on soil fertility indices; (3) assessing spatial and temporal variability in soil fertility across the two settings using geostatistical analysis; (4) testing the hypotheses that urban soils exhibit different fertility status due to intensified management and pollution pressure, and that management intensity mediates observed differences; and (5) formulating evidence-based recommendations for sustainable soil fertility management in peri-urban agriculture. The study adopts a cross-sectional, comparative research design underpinned by the Theory of Planned Behavior and the Sustainable Soil Management framework to link farmer practices with soil outcomes. The population comprises smallholder and peri-urban farms within the metropolitan fringe and adjacent rural districts. A stratified random sampling approach yields 120 farm plots (60 urban, 60 rural), ensuring representation of dominant cropping systems and management intensities. Data collection employs standardized soil sampling at 0–20 cm and 20–40 cm depths, coupled with farmer interviews using a structured questionnaire to capture management regimes, input use, and socio-economic context. Laboratory analyses follow established protocols soil pH, electrical conductivity, organic carbon by Walkley-Black method, total nitrogen by Kjeldahl digestion, available phosphorus by Olsen method, cation exchange capacity via ammonium acetate, and micronutrient status by ICP-OES; microbial biomass carbon and nitrogen via chloroform fumigation-extraction; and enzyme activities (urease, phosphatase, and ?-glucosidase) as functional indicators of soil biota. Spatial data are integrated through kriging to map fertility indices across landscapes. Data analysis employs descriptive statistics and inferential tests (t-tests or Mann-Whitney U tests depending on normality) to compare urban and rural soils, multivariate analysis (PCA) to reduce dimensionality of fertility indicators, and multiple regression to quantify the contributions of management practices and environmental factors to soil fertility. A mixed-effects model accounts for plot-level nestedness and temporal variability where applicable. Validity and reliability are ensured through standard reference materials, duplicate laboratory analyses, instrument calibration, and pilot testing of the interview instrument. Ethical considerations address informed consent, participant confidentiality, and data protection. Expected findings indicate that urban soils will display higher salinity and variable pH, greater organic matter fluctuations, and altered microbial biomass due to distinctive inputs such as compost, urban waste amendments, and potential pollution, while rural soils are anticipated to reflect more stable mineral nutrient profiles but lower organic carbon in intensively cropped plots. The study is likely to reveal that management intensity mediates fertility disparities, with organic amendments and diversified cropping systems mitigating some urban site limitations. Spatial analysis is expected to uncover heterogeneity within settings, highlighting hotspots of both fertility advantage and degradation linked to infrastructure and traffic corridors in urban areas. The study contributes to knowledge by providing a robust, cross-setting assessment of soil fertility determinants in peri-urban contexts, linking agronomic practices with soil health outcomes, and offering evidence-based, regionally transferable recommendations for optimizing soil fertility in rapidly expanding urban agriculture. The main conclusion is that targeted management interventions—emphasizing organic matter restoration, appropriate nutrient budgeting, and pollution-aware practices—are essential to harmonize soil fertility across urban and rural farms. Practical recommendations include the adoption of site-specific nutrient management plans, reinforcement of composting and green manuring programs in urban plots, improved irrigation efficiency, routine soil monitoring with emphasis on pH and salinity, and policy measures to support sustainable peri-urban soil stewardship and investment in soil health education for farmers.