There are decided advantages to fall fertilizer application. It reduces the workload from the spring to fall and seed operations can be dramatically improved. It also helps to reduce fertilizer handling when seeding. There is a financial benefit, as well, since fertilizer prices are usually lower in the fall. Finally, since soil is usually drier, there are fewer problems with compacted soil in the subsequent crop.
Fall fertilizer application can be a challenging process, however. Soil temperatures begin to hover at freezing this time of year and can lead to a loss of nutrients in the soil.
Crop specialists recommend that farmers delay anhydrous ammonia applications until temperatures fall lower than 50 degrees. However, if the ground is near freezing, things become more complicated.
If you are making fertilizer applications in the late fall, keep the following in mind:
- If a hard freeze is in the forecast, don’t apply fertilizer. Don’t apply to frozen or snow-covered ground, either. Nutrients will not remain in the soil in such conditions.
- Always till the soil if you are applying fall fertilizer to soybean stubble. Tillage is the best way to prevent runoff provided it doesn’t no increase soil erosion. Tillage that reduces movement of water also reduce nutrient loss. Remember, nutrients left on the surface are subject to loss.
- Seal the ground behind the knives when applying anhydrous ammonia. As a gas, anhydrous must be appropriately sealed. Cold weather does not equal loss prevention.
- Urea must convert to ammonium if it is to be held by the soil. However, this conversion will not occur when soil is frozen. If urea applications are used, it must be incorporated. Keep in mind that ammonia volatilization is always a danger, including in cool soil, if it has not been properly incorporated.
- There may be a risk of spring loss when fall fertilizers are applied. Fertilizers are soluble in water so will move along with water if there is runoff. If applied to frozen ground, not only will it fail to react with soil, there is a good chance it will be lost when water moves on the soil. In such cases, wait until the spring to apply fertilizer to prevent potential loss of nutrients.
In the end, farmers must weigh the advantages and disadvantages of applying fall fertilizer respective to their specific climate and operation. No matter what decision they make, proper management is the key to success.