Tuesday, November 14, 2006

Influence of Conservation Tillage and Glyphosate on Soil Structure and Organic Carbon Fractions Through the Cycle of a 3-Year Potato Rotation.

Martin R. Carter, Delmar Holmstrom, Brian Sanderson, and Jerry A. Ivany. Agriculture & Agri-Food Canada, 440 University Avenue, Charlottetown, PE C1A 4N6, Canada

Conservation tillage (CT) practices are promising management options for potato (Solanum tuberosum L.) production in Atlantic Canada, however, concerns are expressed about the effects of glyphosate [N-(phosphonomethyl) glycine] on soil structure. The objective of the study was to compare the effects of a four (from conventional to CT) tillage practices (with and without glyphosate) on several soil properties over each phase of a 3-year potato rotation over a five year period. The influence of glyphosate was determined on several soil biological and structural indicators at five stages in the 3-year rotation cycle. Tillage induced changes were evident for most of the soil properties at the pre-spring tillage and pre-ridge tillage stages. Periodic influences of glyphosate on soil properties were ecologically negligible and related to loss of red clover biomass forfeited by early application of glyphosate in the autumn, rather than a direct effect of the herbicide. Overall, use of glyphosate in CT systems on sandy loam soils had no detrimental effect on soil biological properties and associated processes such as soil aggregation.