Winter annual weeds can interfere directly with crops and serve as alternative hosts for important pests, particularly in reduced tillage systems. Field experiments were conducted on loamy sand soils at two sites in Holt, MI, between 2008 and 2011 to evaluate the relative effects of cereal rye, hairy vetch, and rye–vetch mixture cover crops on the biomass and density of winter annual weed communities. All cover crop treatments significantly reduced total weed biomass compared with a no-cover-crop control, with suppression ranging from 71 to 91% for vetch to 95 to 98% for rye. In all trials, the density of nonmustard family broadleaf weeds was either not suppressed or suppressed equally by all cover crop treatments. In contrast, the density of mustard family weed species was suppressed more by rye and rye–vetch mixtures than by vetch. Cover crops were more consistently suppressive of weed dry weight per plant than of weed density, with rye-containing cover crops generally more suppressive than vetch. Overall, rye was most effective at suppressing winter annual weeds; however, rye–vetch mixtures can match the level of control achieved by rye, in addition to providing a potential source of fixed nitrogen for subsequent cash crops.

Cereal-legume cover crop mixtures have the potential to combine the unique strengths of the component species while taking advantage of interspeci c synergies. However, the relative proportion of each species in the mixture is likely to in uence species interactions and entail important tradeo s in cover crop performance. e objective of this study was to evaluate how the relative proportions of cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) sown in mixtures in uenced cover crop biomass production, winter annual weed suppression, vetch winter survival, and vetch N 2 xation as measured by the 15 N natural abundance method. Following a replacement series design, treatments consisted of a gradient of seven rye-vetch mixture proportions ranging from 100% vetch to 100% rye. Density and biomass composition in the mixtures were highly correlated with rye and vetch seeding rates, with little evidence of substantial interspeci c interference. Total shoot biomass in all mixtures was equal to or greater than that of either monoculture, but no di erences were detected in vetch winter survival or the e ciency of N 2 xation. Changing the proportions of rye and vetch in the mixtures resulted in tradeo s related to N and weed management goals. Increasing vetch in mixtures led to greater xed N accumulation but also increased seed costs and reduced winter annual weed suppression. A greater understanding of how rye-vetch mixture proportions in uence cover crop performance can support more-informed decision-making regarding cover crop selection and mixture seeding rates.

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Mixtures of cereal rye (Secale cereale L.) and the legume hairy vetch (Vicia villosa Roth) are used to provide fixed N in balance with other important cover crop services, but late planting and interference from rye can limit vetch productivity. This 2‐yr study in Michigan investigated how fall planting dates influence rye–vetch cover crop biomass quantity and quality in the spring, and evaluated whether staggering (delaying) rye seeding could improve vetch performance (biomass production, N fixation, and winter survival) in mixtures. Treatments consisted of a two‐way factorial of three vetch planting dates (late August, mid‐September, and late September) and three lengths of rye seeding stagger (co‐seeded, short stagger, and long stagger). Later planting of co‐seeded mixtures generally led to reduced total shoot biomass and lower proportions of vetch, resulting in cover crop residues with less vetch N and a higher total C/N. For earlier planting dates, delaying rye seeding until vetch emergence (short stagger) increased vetch shoot biomass by 760 to 1060 kg ha−1 (30–36 kg vetch N ha−1) relative to co‐seeding. Staggered seeding provided no benefit to vetch biomass at later planting dates, and delaying rye seeding until the vetch three to four leaf stage (long stagger) reduced vetch winter survival by 12 to 42% compared with co‐seeding. Additional research is needed to determine whether potential on‐farm benefits of rye–vetch staggered seeding justify the additional management complexity involved and possible tradeoffs with other cover crop services.

Currently accepted pedotransfer functions show negligible effect of managementinduced changes to soil organic carbon (SOC) on plant available water holding capacity (θ AWHC ), while some studies show the ability to substantially increase θ AWHC through management. The Soil Health Institute's North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (θ FC ) and permanent wilting point (θ PWP ). New pedotransfer functions had predictions of θ AWHC that were similarly accurate compared with Saxton and Rawls when tested on samples from the National Soil Characterization database. Further, the new pedotransfer functions showed substantial effects of soil calcareousness and SOC on θ AWHC . For an increase in SOC of 10 g kg -1 (1%) in noncalcareous soils, an average increase in θ AWHC of 3.0 mm 100 mm -1 soil (0.03 m 3 m -3 ) on average across all soil texture classes was found. This SOC related increase in θ AWHC is about double previous estimates. Calcareous soils had an increase in θ AWHC of 1.2 mm 100 mm -1 soil associated with a 10 g kg -1 increase in SOC, across all soil texture classes. New equations can aid in quantifying benefits of soil management practices that increase SOC and can be used to model the effect of changes in management on drought resilience.