Keep It Green: Ecosystem Services of Year-Round Cropping.

1.0 PM CEU

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In many regions of North America arable lands often are fallowed during part of the year. This practice replenishes soil water in arid areas. Where rain is more plentiful, however, fallowing may reflect lack of crops that can survive severe winters; or crops that can, but they generate lackluster economic returns. Using the Upper Midwest as an example, fallowing leaves many fields barren of living plants from September through April and often well into May and even June for some slow-developing crops.

The absence of vigorous crops in arable fields during fallows leads to a long list of negative consequences. These concerns include niche voids filled by resistant weeds, large pools of labile nutrients, and exposed soils with heightened erosion risks. Year-round cropping helps solve all of these problems.

Stocking fields with living crop plants all year is the basis of the Forever Green Initiative (FGI) in Minnesota (http://www.forevergreen.umn.edu/), which is spearheaded by the University of Minnesota, sponsored by the Minnesota legislature, and involves an array of other public and private organizations both within the state and beyond. FGI’s promotion of year-round cropping does not exclude traditional crops such as corn and soybean. Indeed, FGI is working with traditional commodity groups to help integrate “cash cover crops” into conventional summer crop rotations.

Because cash cover crops generate economic returns, they likely have more appeal to growers than standard cover crops. Examples include winter-hardy lines of the oilseeds, camelina and pennycress, which can be sown as late as October and harvested in June. Prior to cover crop harvest, full-season soybean (and other crops) can be interseeded in the cash cover crops and harvested at the usual time in September. Aggregate seed yields, oil yields, and economic returns are higher than in conventional “mono-cropping.” As importantly, this new system suppresses populations of weeds prone to herbicide resistance; sequesters N and reduces nitrate leaching; inhibits erosion and prevents phosphate losses through overland flow; and when the oilseeds flower in early spring (April and May), they provide abundant pollen and nectar for hungry pollinators awakening from hibernation. The services fostered by continually green agricultural fields mean that cropping can enhance, not diminish, the sustainability of agroecosystems.