Farming system-induced variability of some soil properties in a sub-humid zone of Ghana

This study assessed the effects of different farming systems, namely woodlo t (WL), alley farming (AL), conventional tillage (CT) and natural fallow (N F) on the variability of organic carbon (OC) content and mean weight diamet er (MWD) of a degraded Ferric Acrisol in the sub-humid zone of Ghana. The s oils under woodlot accumulated the highest amount of organic carbon (18.6 g kg(-1)) with the least spatial variability apparently due to the greater a dditions of litter and minimum tillage. The conventionally tilled soil had the least OC content (13.1 g kg(-1)). Similar to the OC content, the woodlo t soils also had the highest aggregate stability (MWD = 1.78 mm) and the le ast spatial variability. The stability of soil aggregates under the farming systems was greatly influenced by OC content; there was a good correlation between OC and MWD (r > 0.62**). Correlograms showed that OC and MWD are s pace dependent. The correlation length for OC under the different farming s ystems followed the order WL > NF > AL > CT, indicating that WL ensured a g reater uniform distribution soil organic matter. The spatial distribution i n MWD followed the same trend observed for OC. The MWD in the other farming systems was poorly related from point to point with shorter k-values, sugg esting lack of uniformity due to low accumulation of OC. Generally, the woo dlot system appeared to be a better, low-input restorer of soil productivit y.