Understanding the \"Root\" Cause of Soil Compaction
Agronomy & Pest Management
James Hoorman
Assistant Professor
Ohio State University Extension
Ottawa
Abstract
Farmers vertically till subsoil to reduce soil compaction and increase farmer yields. Tillage temporarily reduces soil compaction but heavy equipment, rain, and gravity compact the soil again. Soil compaction has a biological component. Long-term continuous no-till plus a cover crop reduce soil compaction five ways. Organic residues on the soil surface reduces soil oxygen and cushions soil from heavy equipment. Plant roots create macropores for soil air and water movement. Residual organic soil residues (plants, roots, microbes) are less dense (0.6 g/cm3) than soil particles (1.45 g/cm3). Microaggregate soil particles (clay, silt, particulate organic matter) are held together by the stable humus fraction which are dense and resistant to decomposition. Macroaggregates form by combining microaggregates with root exudates and glycoproteins (polysaccharides and glomalin formed from plants sugars and mycorrhizal fungus). Polysaccharides and glomalin are active soil organic matter (SOM) which stabilize and improve soil structure, however; active SOM is also consumed by bacteria so it needs to be continually reproduced. Macroaggregate soil formation reduces soil compaction. Tillage and subsoiling increases the soil oxygen content and oxidizes active SOM resulting in decreased macroaggregates, poor soil structure and denser soils (soil compaction). In a typical conventional corn-soybean rotation, active roots are present only 32% of the calendar year. New research shows that soil compaction is related to the amount of living active roots. Agricultural systems that have more live roots (hay, pasture, no-till plus cover crop systems) have less soil compaction. A goal is to have a living growing crop year-round.
Authors: Hoorman, J.
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Hoorman, J. Extension Educator, Cover Crops & Water Quality, Ohio State University Extension, Ohio, 45841