Soil physical properties and carbon/nitrogen relationships in stable aggregates under legume and grass fallow

Short-season fallow with legumes and/or grasses can restore the soil organic C and nitrogen (N) and improve soil structure. In this study, we accessed the effects of 2-season legume and grass fallow on structural properties and C/N relationships in aggregates of a sandy loam soil. Two legumes (Calopogonium mucunoides and Centrosema pubescens), and two grasses (Guinea grass (Panicum maximum) and goose grass (Eleusine indica) were used. Results showed that Calopogonium and Centrosema increased soil total porosity and reduced soil bulk densities, while goose grass increased bulk density and reduced total porosity of the soils at 0–15 and 15–30 cm depths. Guinea grass significantly increased the saturated hydraulic conductivity (50.4 cmh−1) andwaterholdingcapacity of the soils. Aggregates, 4.75 to 0.5 mm were greater in Guinea grass and least in goose grass fallowed soils. Calopogonium increased macro-aggregates at 0–15 cm soils by 48%, and mean weight diameter (MWD) by 44%. Organic carbon in 0.5–0.25 mm and b0.25 mm aggregate sizes was higher in Guinea grass soils. Generally, grasses had 4-fold increases of C:N contents in dry aggregates. In conclusion, short-season fallow with Guinea grass, Calopogonium and Centrosema, increased soil C and N and protected themfromlosses in stable aggregates.