By Andi Anderson
Harvest is in full swing, and many farmers are starting to think about manure applications. However, it is important to consider the timing of manure applications, as applying manure to warm soils can waste nitrogen.
Why is it important to delay manure applications?
When manure is applied to warm soils, it is quickly converted to ammonium nitrate. Ammonium nitrate is a volatile form of nitrogen that can easily escape into the atmosphere as ammonia gas. This process is known as ammonia volatilization.
In addition to ammonia volatilization, nitrogen can also be lost through leaching. Leaching occurs when water moves through the soil and carries dissolved nutrients with it. Nitrogen is more likely to leach when soils are warm and wet.
By delaying manure applications until soil temperatures are cool enough, farmers can reduce the risk of nitrogen loss through ammonia volatilization and leaching.
When is it safe to apply manure?
It is safe to apply manure when soil temperatures are 50 degrees Fahrenheit or cooler. This is the same temperature threshold that is recommended for anhydrous ammonia applications.
To monitor soil temperatures, farmers can use the ISU Soil Moisture Network County 4 inch Soil Temperature Maps.
What are the benefits of delaying manure applications?
Research has shown that delaying manure applications can improve crop yields. This is because more of the manure nitrogen is available for use by the crop when it is applied to cool soils.
One study found that delaying high-ammonium manure application by six weeks resulted in a corn yield advantage of 19 bushels per acre.
What are some other ways to reduce nitrogen loss from manure?
In addition to delaying manure applications, farmers can also reduce nitrogen loss by:
- Injecting manure into the soil. Injection helps to reduce ammonia volatilization by placing the manure below the surface of the soil.
- Applying manure to cover crops. Cover crops can utilize manure nitrogen and reduce the risk of leaching.
- Avoiding manure applications on frozen soils. Frozen soils are more likely to experience leaching when they thaw.
By delaying manure applications and following other best management practices, farmers can save money on nitrogen fertilizer and reduce the environmental impact of manure.
Categories: Iowa, Crops