Organic Farming and Soil Physical Properties: An Assessment after 40 Years

Organic farming is one environmentally viable approach to agriculture through its use of animal and green manures to provide nutrients and cultural practices to manage weeds, insects, and pathogens. The sustainability of organic agriculture, however, is less well understood, especially under long-term management. A study was conducted near Mead, NE, to investigate the long-term impacts of organic management on soil physical properties including soil aggregate stability, bulk density, Proctor bulk density (parameter of soil's susceptibility to compaction), water infiltration, saturated hydraulic conductivity, and soil-water retention characteristics in conventional farming (CR1), conventional farming with diversified rotation (DIR), organic practices with green manure (OGM), and organic practices with animal manure (OAM). The OGM and OAM treatments increased cumulative water infiltration by about 10 times compared with the CR1 treatment, indicating that organic farming can increase water storage relative to conventional systems. Mean weight diameter of water-stable soil aggregates increased by 50% with the OGM and by 30% with the OAM treatments in the upper 15-cm depth, indicating that aggregates were larger and more stable under organic than conventional practices. At the same depth, the Proctor bulk density was 3% lower under organic practices than in the CR1 treatment, suggesting that organic farming reduces the soil's susceptibility to compaction. The increase in aggregate stability and porosity increased water infi ltration and saturated hydraulic conductivity. Overall, organic farming can improve soil physical properties in the long term and provide a strategy for farmers to enhance soil physical quality and agricultural sustainability.