The long-term influence of reduced tillage on weed and soil factors.
10 yr after establishing different tillage and no-till systems in a maize/soyabean rotation, total weed yield was highest in the no-till and lowest in the conventional system. The predominant grasses in no-till were green foxtail [Setaria viridis], field sandbur [Cenchrus incertus], barnyardgrass [Echinochloa crus-galli] and foxtail barley [Hordeum jubatum]. Broadleaf weeds varied greatly between no-till, min. tillage, reduced cultivation and conventional systems. They include Pennsylvania smartweed [Polygonum pensylvanicum] and redroot pigweed [Amaranthus retroflexus] in no-till and common cocklebur [Xanthium pensylvanicum] in min. and conventional tillage. Perennial weed distribution differed little between tillage systems. Soil OM, pH, soluble salts, nitrates, P, K and bulk density did not differ between systems below 30 cm. OM, P and K were concentrated at the soil surface in no-till and min. tillage. Bulk density was greatest in the upper 15 cm of reduced tillage.