Physical properties of a sandy loam Ultisol as affected by tillage-mulch management practices and cropping systems

Abstract

Evaluation of the impact of tillage-mulch practices under different cropping systems on soil physical properties is needed in southeastern Nigeria to identify those combinations with the potential of alleviating the physical constraints of the Ultisols predominant in the area. An investigation was carried out on a sandy loam soil at Nsukka to determine the effects of no-till (NT) and conventional tillage (CT) each with bare fallow (B) and mulch cover (M) on soil physical properties under three cropping systems [sole sorghum ( Sorghum bicolor L. Moench), sole soybean ( Glycine max L. Merrill), and sorghum-soybean intercrop]. The layout was a split-plot in randomized complete block design, with the tillage systems as the main plots and the mulch practices as the sub-plots. The treatments [no-till and bare (NTB), no-till with mulch (NTM), conventional tillage and bare (CTB) and conventional tillage with mulch (CTM)] were replicated four times. The selected key parameters evaluated after two years were density of earthworm casts, soil organic matter (SOM), bulk density (BD), total porosity (TP), pore size distribution (PSD), mean weight diameter (MWD), and saturated hydraulic conductivity (K sat). Earthworm activity was significantly ( P ≤ 0.001) higher with NT under the intercrop system. Values were generally very low for SOM (1.06-1.48%), moderate for BD (1.34-1.51 Mg m −3) and TP (46-52%), and low to moderate for MWD (1.1-2.9 mm). The K sat was within the slow to rapid range (8.1-57.0 cm h −1). Neither the tillage nor the mulch factors influenced SOM, BD, PSD, and MWD in the cropping systems. The TP was significantly ( P ≤ 0.05) higher in the CT compared to the NT under the sole sorghum, where interaction showed higher value in the CTM compared to the rest. There was significant ( P ≤ 0.05) enhancement of K sat in the CT under the sole sorghum and the intercrop systems; whereas the value was significantly ( P ≤ 0.01) higher in the bare fallow under the sole soybean. The cropping systems had more pronounced effect on the physical properties than the tillage-mulch management practices. All the measured parameters indicated significant ( P ≤ 0.05) improvements under the sole soybean, except BD and MWD which were significantly ( P ≤ 0.05) improved under the intercrop. Intercropping cereals and legumes on NT may be ideal for alleviating the soil's structural constraints.