Root growth, calcite precipitation, and gas and water movement in fractures and macropores: A review with field observations

Recent research on the presence and dynamic nature of fractures and soil ma cropores has generated interest in their impact on root growth in minimally disturbed soils due to no-till or reduced tillage farming practices. The b alance of water, air, and nutrients in the subsurface Is, in part, determin ed by the structure and type of macropores, Biological systems can create a nd expand the network of biopores, or change the biogeochemistry within a g iven fracture or biopore, In the field, roots have been observed to grow pr eferentially through fractures. At a demonstration test pit at The Ohio Sta te University (OSU) Molly Caren Agricultural Research Center In London, OH, networks of roots were exposed within fractures at 1.0 to 2.0 m in depth. A streambank on the OSU Waterman Agricultural and Natural Resources Laborat ory in Columbus, OH, provided a natural exposure of fractures and roots pre ferentially growing in these fractures at depths of 1.0 to 1.5 m, A deeply incised streamcut in Batavia, OH, revealed live roots growing Cat a depth o f 15 to 20 m) within pre-Illinoian glacial till fractures. Microbial action upon living roots and in the degradation of dead root material can lead to calcite precipitation and infilling of fractures and other macropores. Ear thworm burrowing can redistribute nutrients to the deeper subsurface, facil itating root growth at greater depths. During construction of the small tes t pit located near Tremont City, OH, a live earthworm was observed within a fracture at a depth of approximately 3.0 m.