A cover crop of rye grass comes up in a field in eastern Nebraska. Cover crops help hold moisture and nitrogen in the soil. They can reduce nitrate runoff and erosion. Grant Gerlock/Harvest Public Media hide caption

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Carp are collected at a breeding farm near the Belarus village of Ozerny in November 2013. Researchers say there's a lot the aquaculture industry can do to be more efficient. Viktor Drachev/AFP/Getty Images hide caption

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