A critical question is whether there are agricultural management practices that can attain the multiple management goals of increasing yields, preventing nutrient losses, and suppressing greenhouse gas (GHG) emissions. No-till and manure application methods, such as manure injection, can enhance nutrient retention, but both may also enhance emissions of nitrous oxide (N 2 O), a powerful GHG. We assessed differences in soil N 2 O and carbon dioxide (CO 2) emissions, nitrate and ammonium retention, and crop yield and protein content under combinations of vertical-till, no-till, manure injection, and manure broadcast without incorporation in a corn (Zea mays L.) silage system. During the growing seasons of 2015-2017, GHG emissions and soil mineral nitrogen (N) were measured every other week or more frequently after management events. Crop yield and protein content were measured annually at harvest. No-till reduced CO 2 emissions but had no impact on N 2 O emissions relative to vertical-till. Manure injection increased N 2 O and CO 2 emissions, with the magnitude of this effect being greatest for 1 mo post-application. Manure injection also increased soil ammonium and nitrate but did not increase yield or crop quality relative to broadcast application. Similarly, tillage did not affect crop yield or protein content. Despite the tradeoffs between mineral N retention and elevated GHG emissions, manure injection in no-till systems benefits farmers by reducing soil carbon losses as CO 2 , retaining mineral N, and maintaining crop yields and quality.
A research team at UVM, led by Dr. Carol Adair and Dr. Heather Darby, is evaluating the benefits and drawbacks of four different tillage approaches (conventional, strip, vertical, and no till) and two different methods of manure application (broadcast and injection). The goal is to determine the practices best suited for reducing greenhouse gas emission, improving carbon storage and limiting nitrogen losses. The team measures carbon dioxide and nitrous oxide emissions from the treatments every two weeks or more frequently after events (large rainfall, manure application) using a measuring device called photoacoustic multigas monitor.
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