Reduced tillage (RT) practices provide a number of ecological and agronomic benefits, but may also result in reduced inorganic nitrogen (N) availability and greater weed competition. These challenges are especially difficult on organic farms, where fertilizer and herbicide options are limited. My dissertation aims to adapt RT systems for organic production by addressing critical barriers to adoption: N deficiency and weeds. First, I conducted a survey to determine Michigan organic farmers’ current tillage practices and attitudes towards RT. Second, I evaluated the effect that one form of reduced tillage, strip-tillage (ST), has on N dynamics within an organic system. Finally, I evaluated how varying cover crop spatial arrangements within ST might mediate RT challenges; specifically how strip-intercropping of cereal rye and hairy vetch affects cover crop biomass and N, soil and sweet corn N, and weeds. Our survey documented a wide range of current tillage frequencies associated with production of specific organic crops. Despite an overall high level of awareness of the benefits of RT, interest in adoption of specific RT practices among organic farmers was fairly low. Among RT options, vegetable farmers were most interested in permanent beds and strip-tillage and field crop producers in rotational tillage, followed by strip-tillage. The greatest perceived barriers to RT adoption were weeds, residue management, crop establishment, impact on yields and obtaining RT equipment. Strip-tillage (ST) confines soil disturbance and incorporation of organic residues to a narrow strip directly within the crop row. We conducted field studies in southwest Michigan from 2011 to 2014 to examine the effects of tillage (ST vs full-width tillage [FWT]), on soil N and weeds under various levels of cover cropping and weed management. Compared to FWT, ST had lower inorganic N availability both within and between crop rows. Additionally, ST increased the concentration of N within the soil leachate and the potential for N to be lost through denitrification. Despite lower soil N, ST only negatively impacted sweet corn biomass and N uptake in 1 out of 3 years and increased yields in 1 out of 3 years. ST had varying effects on weed emergence and biomass, which was largely dependent on cover crop biomass. In 2012, rye-vetch biomass was between 7.0 and 8.0 Mg ha-1, and reduced weed emergence and biomass within ST, resulting in greater sweet corn yield under low weed management. However, in 2013 rye-vetch biomass was approximately 35% lower, weed biomass higher, and yields reduced in ST compared to FWT. To address the challenges of residue management and N deficiency within organic RT, we compared standard full-width mixtures of rye and vetch cover crops, to a novel “strip-intercropping” arrangement in which rye was planted only between future crop rows, and vetch planted only in-line with future crop rows. Strip-intercropping resulted in a lower C:N ratio of residue and higher N mineralization within the crop zone, but had no effect on weeds, or corn yield, biomass, or N uptake. To increase the potential benefits of strip-intercropping, future research efforts should focus on cover crop mixtures and termination methods which minimize the movement of shoot tissue across zones.
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