Effects of Topsoil Removal and Amendments on Soil Bulk Density and Maize Yield in the Southern Guinea Savanna of Nigeria

Effects of topsoil removal and amendments on soil bulk density and maize production in the Southern Guinea Savanna of Nigeria were studied during 2012 and 2013 cropping seasons. A split-split plot experiment in a Randomized Complete Block Design, with three replications was conducted. The factors were topsoil removal; cropping systems and amendments. Soil physical and chemical properties were analyzed before planting and after harvest. Maize (Zea mays L.) growth and yield parameters were evaluated. Bulk density increased significantly (P = .05) at Otobi from 1.39 to 1.58 g cm-3 in 2012 and from 1.40 to 1.54 g cm-3 in 2013, as topsoil removal increased from 0 to 20 cm. There were significant relationships between topsoil removal and the organic matter (OM) content of the soil. For every centimeter (cm) of topsoil removal, OM decreased by 0.04 g kg-1 in 2012 and 0.10 g kg-1 in 2013 at Makurdi. Meanwhile, at Otobi, the loss of 0 – 1 cm depth of topsoil resulted in the decrease in OM content by 0.06 g kg-1 (2012) and 0.07 g kg-1 (2013).The application of poultry manure (PM) significantly improved maize grain yield at Makurdi (2868 and 2804 kg ha-1)and Otobi (2836 and 2393 kg ha-1) in 2012 and 2013 seasons. The interaction between topsoil removal and soil amendments suggests that at higher depth, application of either PM or inorganic fertilizer may not differ significantly in maize grain yield after first season cropping. The yield advantage of PM relative to other treatments suggested the efficacy of PM as a better soil management option that enhances the restoration of the productivity of an eroded soil.