Surface crop residue effects on fungal hyphal length, soil organic carbon and soil moisture in oat (Avena sativa) plots

Oats (Avena sativa) were grown in outdoor plots in southern Ontario in 2003 and 2004 to determine if fungal hyphae growth associated with surface residue increased soil moisture and OC through soil aggregation and if the type of residue (oat straw, mixed hay, corn stalks, compost) and plant cover (weeds, alfalfa, oats) altered fungal growth and the soil physical properties as well. OC increased significantly with dried surface residue and alfalfa ground cover over the season of the oat crop in 2003 while the oat plants had a greater effect than surface residue on OC in 2004. Soil moisture and aggregation were increased from straw and corn residue in 2004, but were reduced by the growing oat crop. Hyphal length increased only with interaction of the oat plants and residue in August, 2004 from the 2-way ANOVA analysis. The study results suggest that resistance to decomposition with high residue C/N and surface application is more important to soil OC than the amount of decomposition in moist, sandy, high OC soil conditions.;Keywords. Soil organic carbon, macroaggregates, mycorrhiza, fungal hyphae, surface residue, soil moisture, density fractions, oats, no-till.