SOIL PHYSICAL PROPERTIES, ORGANIC CARBON DYNAMICS, AND MAIZE PERFORMANCE UNDER LONG-TERM GRAZING AND CONTINUOUS CULTIVATION IN ADO EKITI, SOUTHWEST NIGERIA

Abstract

The development of climate smart strategies for improved soil health and sustainable crop production requires an understanding of the responses of soil properties to grazing and cultivation. This study was aimed at quantifying the stock, distribution, and sequestration of soil organic carbon (SOC), soil physical properties, and maize yield on grazed pasture (GP) and cultivated land (CL). Soil samples collected from two adjacent fields: GP and CL, were analysed using standard laboratory procedures. Texturally, the two soils alternated from loamy sand at the surface 20 cm for CLand sandy loam for GP to sandy clay loam for GP and sandy loam for CL respectively at the subsoil. In addition, bulk density and cone index averaged 1.7 and 1.5g/cm3; 4.75 and 2.5kg/cm2 respectively on GP and CL showing higher soil compaction of the soil under GP. With dispersion ratio (DR) standing at 55 and 80 for GP and CL soils respectively indicating more structurally stable aggregates for the GP soil. Higher infiltration rate, saturated hydraulic conductivity and hence soil moisture content were also recorded for the grazed soil. Moreover, after 20 years of cattle grazing, SOC content varied widely from 3 to 13% on the grazed pasture and was significantly higher than on cultivated plot which was less than 1%. At the surface 10cm, SOC stocks of the GPwas almost 10 times higher (136 mg/ha) than that under CL (14mg/ha). Maize yield was 4.3tons/ha on GP in contrast to 0.3 ton/ha) on CL. The heavy SOC addition into the GP soil and the attendant improvements in soil aggregate stability, water retention plus the resultant nutrient level and soil health has further confirmed the benefits that can accrue from integrating light to moderate animal grazing into crop cultivation in a humid tropical environment.