Crop agronomic performance under a six-year continuous organic no-till system and other tilled and conventionally-managed systems in the northern Great Plains of Canada

Abstract

Reducing tillage in herbicide-free cropping systems is a challenge for farmers and few studies have attempted to identify the limitations of organic no-till systems over a period of time greater than two years. The objective of the study was to determine the effect of tillage [no-till (NT) and conservation tillage (CT)] and management [organic (ORG) and conventional (CONV)] systems on mulch biomass, weeds, and crop productivity, over time. A six-year field study was conducted in Carman, MB, Canada, between 2008 and 2012. The crop rotation was barley (Hordeum vulgare L.)/hairy vetch (Vicia villosa Roth) cover crop in 2008, flax (Linum usitatissimum L.) in 2009, oats (Avena sativa L.) followed by a 4-species fall-seeded cover crop mixture in 2010, barley/hairy vetch cover crop in 2011, and spring wheat (Triticum aestivum L.) followed by fall-seeded cereal rye (Secale cereale L.) in 2012. From 2008 until mid-2010, the experiment design consisted of two tillage systems (NT and CT), both under ORG management. In mid-2010, the experiment was modified into a split-plot design to allow for the comparison between the ORG and CONV management systems, within each tillage system. In ORG NT, cash crops of flax and spring wheat were seeded into 4.5 and 4.7Mgha−1 of rolled cover crop mulch in 2009 and 2012, respectively. Differences in weed communities between treatments were statistically noticeable in the fifth year of the study only (2012), with higher weed biomass and weed species richness in the ORG management system. Crop yields were reduced in ORG NT in 2009 (flax) and 2012 (spring wheat). Little difference in weed and crop responses between ORG and CONV tilled systems were identified. Results suggest that additional innovative soil and weed management practices are needed to make organic continuous no-till cropping system productive for a period longer than six years, in a cool subhumid continental climate.