Potential use of underseeded barley to increase carbon inputs to a loam soil in the New Brunswick potato belt
Organic carbon depletion as a result of intensive potato production is a serious concern in northwestern New Brunswick, Canada. Underseeding of rotational grain crops with selected grasses and legumes is being used by farmers to increase crop residues in order to maintain soil organic carbon levels. The objectives of this study were to quantify changes in selected soil propertiesm, effects on grain yield, and increases in total biomass production resulting from different underseeding treatments on a Caribou fine-loamy Brunisolic Gray Luvisol. Clovers, ryegrasses and a mixture of timothy, Alsike and red clover were underseeded in Chapais barley plots. Underseeding did little to improve soil bulk density, macroporosity and saturated hydraulic conductivity of the upper plow layer (4–12 cm depth) over one growing season. Averaged over a 3-yr period, underseeding did not significantly affect barley grain yields; however, annual reductions of up to 17% were experienced with some of the more aggressive companion crops, such as Lemtal Italian ryegrass. Underseeding significantly increased total biomass contributions (residues) to the upper 20 cm of the soil by 40 to 90%, making the year in grain production a potential net organic carbon supplier rather than an organic carbon depletor. Key words: Companion crop, roots, soil organic carbon, soil bulk density, soil permeability, crop residue