Protection from wintertime rainfall reduces nutrient losses and greenhouse gas emissions during the decomposition of poultry and horse manure-based amendments

<p>Manure-based soil amendments (herein “amendments”) are important fertility sources but differences among amendment types and management can significantly affect their nutrient value and environmental impacts. We conducted a six-month in situ decomposition experiment to determine how protection from wintertime rainfall affected nutrient losses and greenhouse gas (GHG) emissions in poultry (chicken broiler and turkey) and horse amendments. We measured changes in total nutrient concentration – nitrogen (N), phosphorus (P), and potassium (K) – every three months, changes in ammonium (NH<sub>4</sub><sup>+</sup>) and nitrate (NO<sub>3</sub><sup>−</sup>) concentration every month, and GHG emissions of carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>), and nitrous oxide (N<sub>2</sub>O) every 7–14 days. Poultry amendments maintained higher nutrient concentrations (except for K), higher emissions of CO<sub>2</sub> and N<sub>2</sub>O, and lower CH<sub>4</sub> emissions than horse amendments. Exposing amendments to rainfall increased total N and NH<sub>4</sub><sup>+</sup> losses in poultry amendments, P losses in turkey and horse amendments, and K losses and cumulative N<sub>2</sub>O emissions for all amendments. However, it did not affect CO<sub>2</sub> or CH<sub>4</sub> emissions. Overall, rainfall exposure would decrease total N inputs by 37% (horse), 59% (chicken broiler) or 74% (turkey) for a given application rate (wet weight basis) after six months of decomposition, with similar losses for NH<sub>4</sub><sup>+</sup> (69–96%), P (41–73%), and K (91–97%). Our results confirm the benefits of facilities protected from rainfall to reduce nutrient losses and GHG emissions during amendment decomposition.</p> <p><b>Implications</b>: We monitored the impact of rainfall protection on nutrient losses and greenhouse gas emissions during the decomposition of broiler chicken, turkey and horse manure-based soil amendments. We found large ammonium and potassium losses when amendments were exposed to rainfall, resulting in a 37–74% decrease in N inputs when compared to amendments protected from rainfall. Nitrous oxide emissions were also higher with rainfall exposure, although it had no effect on carbon dioxide and methane. Overall, this work highlights the benefits of rainfall protection during amendment decomposition to reduce nutrient losses and GHG emissions.</p>