A Comparative Analysis of the Effects of Organic and Conventional Farming Systems on Soil Structure

Abstract

ABSTRACT In the past decade there has been increasing scientific interest in organic farming, especially in comparison with commercial agriculture. Although many comparative studies involving these two agricultural systems have been undertaken, few assess the impact of these two fundamentally differing systems on soil structure, and none on soil microstructure. In this study, two adjacent, paired farms in eastern Iowa, one managed according to organic, and the other according to conventional, farming methods, were studied to determine the effects of these two agricultural systems on soil structure and microstructure. At both farms colour, texture, ped type and degree of development, depth of the A horizon and porosity were described in the field, organic matter content was determined, and microstructural and organic characteristics were described using micro-morphology. The organic farm had a significantly ameliorated soil structure: with an increased A horizon depth, organic matter content, porosity, earthworm abundance and activity, and coarser, better developed aggregates than the conventional farm. Moreover, the conventional farm also suffered from compaction and erosion. This study indicates that, over the long-term, organic management methods are able to maintain and improve the structure of the soil, resulting in a soil with tilth more conducive to promoting crop growth, than conventional methods which degrade the soil.