Soil Respiration Rates Under Different Crop Residue Management Practices in Anambra State, South East Nigeria

This study measures soil respiration rates under contrasting crop residue management practices in smallholder farms in Anambra State, located in Nigeria's South East geopolitical zone. Soil respiration is a sensitive biological indicator of soil organic matter decomposition activity and microbial community function, and its response to residue management has implications for both soil fertility maintenance and greenhouse gas emissions from agricultural soils. Using a field measurement design, soil CO2 efflux was measured monthly over eight months using static alkali absorption chambers on plots with four residue management treatments: open field burning, complete residue removal, residue retention on the soil surface, and residue incorporation by shallow tillage. Three replicate plots per treatment were established on sandy loam soils in Ogbaru and Onitsha North local government areas. Soil organic carbon, microbial biomass, and moisture content were measured concurrently on each measurement date. Findings revealed that residue incorporation produced the highest mean soil respiration rates (2.8 g CO2-C per square metre per day) and the greatest gains in organic carbon over the study period. Residue retention on the surface showed intermediate respiration rates while burning produced the lowest values. Seasonal moisture patterns strongly modulated respiration, with peaks after the onset of rainfall. The study recommends residue incorporation as the best practice for sustaining biological activity in Anambra State farming systems, noting that burning eliminates both nutrient return and stimulation of soil biological activity. Keywords: soil respiration, crop residue management, organic carbon, Anambra State, soil biology.