Some Midwest soils, like southern Indiana and Illinois, are noted for layers of compaction. Some were laid down millenia ago - glacial till and so forth. More recently, conventional plowing has created another layer of compaction, just below the deepest plow or ripper.
Neither corn nor soybean roots can penetrate those compacted layers. Rather, the roots hit that layer and then continue to grow laterally. In a good rain year, plants with lateral roots do okay. But in dry years or droughts, look out! The heat in shallow soil goes up and the roots wither along with the crop.
Annual ryegrass roots - when used as a cover crop - penetrate to depths of 60 inches (probably not in the first year of planting, but certainly after three or four). In a dry year, that makes all the difference to corn and soybean roots, which follow the “macropores” in the soil created by the annual ryegrass the previous winter.
The difference in rooting depth for cash crops translates into extra crop yield at harvest time, as much as 50 bushels an acre in some field tests in southern Illinois. For more information, check out www.ryegrasscovercrop.com
Tags: Annual ryegrass, cover crop, crop yield, deep rooting, macropores
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