Applying manure to fields provides a natural and sustainable way to fertilize crops, reducing the need for synthetic fertilizers. It adds essential nutrients like nitrogen, phosphorus, and potassium, improving soil health and promoting plant growth. Additionally, manure enriches the soil with organic matter, enhancing its structure and water-holding capacity. However, there’s a side to manure that many don’t often think about, that is ammonia deposition. Ammonia deposition is the process by which ammonia is returned to the Earth’s surface after being released into the atmosphere.
Understanding Ammonia in Manure
Manure, a valuable resource for fertilizing crops, contains two primary forms of nitrogen: organic nitrogen and ammonium nitrogen. Organic nitrogen, a slow-release form, nourishes plants gradually over time. Ammonium nitrogen, on the other hand, is readily available to plants but is highly volatile. When exposed to air, it can easily evaporate, releasing ammonia gas into the atmosphere.
Things that go into the air, like pollution, eventually fall back to the ground. You've probably noticed how the air smells fresher after a rain shower. That's because rain helps to wash away pollutants like dust and harmful gases from the air. However, pollutants can move with air currents and deposit in areas other than where it was lost, thus the potential for ammonia deposition in places other than where it was lost to the atmosphere initially.
Since 1985, the National Atmospheric Deposition Program has been tracking ammonium ion concentration in precipitation and the increase to date is staggering – especially in the Midwest. Their research has shown that 80% of ammonia emissions come from agriculture and of that, roughly half is from livestock. Of course, livestock with manures that are higher in ammonium N, like swine, are more prone to ammonium losses - especially during manure applications, but losses from beef cattle are nearly as large – mostly losses from the pen surface before the manure is ever collected.
The Impact of Ammonia Deposition
So why does ammonia deposition matter? For the same reasons we worry about nitrates in our groundwater, excessive ammonia in surface water and soil can cause harm to ecosystems, can damage sensitive habitats and affect biodiversity.
Excessive ammonia deposition can lead to a range of environmental problems.
