With less fall N being applied, the trend towards spring and in-season N application continues to grow. 

 

The decision to apply nitrogen in the fall after harvest  is often an economic one - fertilizer prices tend to be lower in the fall and farmers are typically overloaded with other work in the spring, making N application just one more thing to add to the list. Fall application of anhydrous ammonia is often regarded as a ‘safety net’; attempting to ensure crops have access to nitrogen for the following spring, mitigating potential financial risks associated with more expensive nitrogen options and the unknown planting season ahead.

A common misconception is that N loss is at its greatest during extended wet conditions experienced in the spring months and that cold temperatures make it less likely for nitrogen to disappear through leaching. Although the risk of over-winter N loss is typically highest in regions with wetter climates, recent studies show how even severe freezing won’t help retain the fall-applied nitrogen.  A group of Canadian researchers examined the loss of nitrogen through field applications of manure and synthetic nitrogen at sites with various winter climates ranging from above freezing and wet to arid and below freezing. The greatest loss of nitrogen was shown in the cold/wet winter soils, ranging from 70 – 95%. However, even soils experiencing temperatures well below freezing saw overwinter losses of the applied nitrogen between 60 – 75%.

 

The shift from fall anhydrous ammonia application doesn’t have to mean less available N for crops

The fall application of N may be a common practice for peace of mind to ensure crops have enough available N in the spring, however, the potential pitfalls of fall applied N may leave growers looking for an alternative.

1. Much of the N you apply in the fall is gone before the plant needs it. Ammonium can be lost through nitrification and leaching if applied too early in the fall; if the soil is too warm it speeds up the process. Even if it is applied when the soil is cold, nitrification speeds up again in early spring, so you lose the N well before your corn plant needs it.
2. Applying anhydrous ammonia in the fall has environmental impacts as well. When anhydrous is not trapped in the soil, farmers also risk nutrient loss as a result of volatilization, when it gasses off as Nitrous Oxide, a powerful green-house gas contributing to climate change.

When soils are warm and wet, either in late fall or early spring, anhydrous ammonia is at its greatest risk of being washed away through the soil into waterways. As many states experience increased regulations around the use of commercial nitrogen fertilizers, ending fall anhydrous ammonia application also falls in line with best practice “4R Nutrient Stewardship,” that are now being followed in states along the Mississippi River and Chesapeake Bay watershed areas, as well as Minnesota, where fall application will no longer be allowed as of 2020. Fall fertilizer applications still represent a good option within a total fertility program. Having a strong understanding of the strengths and weaknesses of this practice allows farmers to create the best program for their operation. 

 

Fall application may be more convenient, but is it more effective?       

As technology and farming practices evolve, and environmental regulations tighten, farmers will continue to strive for nutrient efficiency - applying N when and where it is most needed by plants without sacrificing yield.     

Envita nitrogen-fixing bacteria gives growers another tool for their nitrogen program without the risk of potential loss associated with soil applied fertilizers. Envita™ is the only nitrogen-fixing bacteria for corn, soybeans and other crops that works from within plant cells to fix nitrogen from root to leaf all season long, replacing an average of 27% of of a corn plant’s nitrogen need. Envita enters the seed at germination, so there is no risk of leaching. It quickly establishes itself within the plant - allowing cells throughout the plant including foliage and roots to fix their own nitrogen directly from the air.

The below image shows how as applied N begins to diminish; plant growth slows. Translocation of soil applied N is more difficult and complicated by environmental and weather conditions. Envita ensures a consistent source of N all season long, maximizing yield potential.

 

Peak demand for nitrogen in corn occurs well after nitrogen fertilizers are typically applied (pre-plant, side dressed, etc.), and months after fall application of anhydrous. Envita ensures your plant has nitrogen where and when the plant needs it most, all season long, maximizing crop growth potential. 

Envita replaces up to 27% of a corn plant’s nitrogen requirements without impacting yield and since it is applied in-furrow during spring planting, it doesn’t require additional time in the field. It provides farmers an environmentally responsible method of diversifying total N application, and a new approach to combating the economic and logistical challenges of nitrogen loss. If you are considering moving away from fall anhydrous, look to Envita for a cost-effective alternative.