Crop cover root channels may alleviate soil compaction effects on soybean crop

Deep-rooted cover crops may help alleviate effects of soil compaction, especially in no-till systems. We evaluate compaction-alleviating ability of three Brassica cover crops and cereal rye (Secale cereale L.). Using a minirhizotron camera, we observed soybean [Glycine Mar (L.) Merr.] roots growing through compacted plowpan soil using channels made by decomposing cover crop roots. Soybean yield response to the preceding cover crops was most pronounced at the site with most severe drought and soil compaction. At this location, with or without deep tillage, soybean yields were significantly greater following a forage radish + rye combination cover crop. Rye left a thick mulch, resulting in conservation of soil water early in the season. Root channels left by forage radish (Raphanus sativus L. 'Diachon') may have provided soybean roots with low resistance paths to subsoil water. Due to lower than normal winter precipitation, this study was a conservative test of the cover crops' ability to alleviate the effects of soil compaction.