Implications of cover crops for soil quality and geodiversity in a humid-temperate region in the midwestern USA

Winter cover cropping plays an important role in conservation farming. In the Midwest region of the USA, strips planted with Austrian winter peas [AWP (Pisum sativum L.)], radishes [RAD (Raphanus sativus L.)], and a mixed cover of both cultivars (MIX) were compared during the spring season to determine their impact on the soil quality at 0-5 and 5-10cm depths. The treatments RAD, AWP, and MIX had the highest, intermediate, and lowest soil bulk density impacts (1·67, 1·52, and 1·50Mgm ^-3, respectively). An opposite trend was observed for the concentrations of soil organic carbon (15·9, 17·6, and 19·4gkg ^-1, respectively) and total nitrogen (1·5, 1·7, and 2·8gkg ^-1, respectively), the calcium exchange capacity (8·6, 9·5, and 11·4 cmol ⁺c kg ^-1, respectively), and earthworm density (85, 221 and 226 per m ² x 0·15m, respectively). The AWP, MIX, and RAD resulted in the highest, intermediate, and lowest water stable aggregates (91·6, 87·4, and 79·9 per cent, respectively), mean weight diameter of aggregates (3·4, 2·7, and 2·1mm, respectively), saturated hydraulic conductivity (15·7, 13·0, and 6·3cmh ^-1, respectively), and intrinsic permeability (1·69, 1·37, and 0·70cm ² 10 ^-10, respectively). The AWP and RAD treatments resulted in a similar C:N ratio (10·5), which was larger than associated with MIX (7·2). Overall, AWP and MIX had a larger positive impact on soil quality than RAD did, and the impact was greater at the 0-5 than the 5-10cm depth. This indicates the suitability of the various cover crops for improving the soil quality and restoring geodiversity.