Nitrogen and Phosphorous BMP's

Now that you have created a Nutrient Management Plan (Plan) for your farm let's take a quick look at some Best Management Practices (BMP's) for applying Nitrogen (N) an Phosphorous (P).

Nitrogen Application

Timing 
Applying N when the crop needs it provides yield, economical, and environmental benefits, so in-season application timing is important. The yield benefit is realized by having the right amount of N available for the crop at critical growth stages.

Credit - Iowa State University Extension

The economic benefit is realized with proper timing as the potential for N loss is reduced. This will prevent having to apply N again, thus increasing input costs without any added benefits from the double application. You can also realize a reduction in the environmental impact of N application with proper timing. For example, applying N with a weather forecast of heavy rains soon following increases the potential of N leaching out of the soil.



Application Rates
With the advances in agronomy and technology, it is possible and also economically beneficial to adopt Variable Rate (VRA) practices on your farm. Applying the proper rate to obtain the maximum economic return while still minimizing your environmental impact is not only feasible but should be done. There are many tools available in your precision agriculture "toolbox" to aid in your VRA practice. Soil sampling and remote sensing (Aerial/Satellite Imagery) can be analyzed to create management zones for each of your fields with ease.

"Indirect" N Sources
There are other activities in the production of your crop that indirectly applies N. Take for example an application of P. You may be applying an ammoniated phosphate to satisfy your P requirements. Well this form of P contains N. It is important to take this into account when determining your application rates so you are not applying more than what is needed. Another indirect source is the application of starter fertilizer when planting. As you did when developing your Plan, be sure to take into account all sources of N

Method of Application
There are multiple forms of N, like anhydrous ammonia, Urea, and UAN solutions. Each will have a method of application. N can be applied via broadcasting, knifing, banding, and direct injection. Each method has it's place and one is not better than the other. It just requires an effective management approach based on your field data. The method you use to apply fertilizer is quite important as it effects other aspects of your production like tillage practices.

Phosphorous Application

Application Rates

There is no need to maintain high levels of P in your soil. Only apply what is dictated by utilizing a soil analysis. Maintaining higher levels of P than is required brings higher costs and higher environmental impacts from runoff. One approach that has proven to work is the adoption of VRA technologies. This will aid in applying the right amount of P where it is needed in your field while not applying P to areas on high P levels. 

Application Method/Placement

P, in contrast to N does not "move" rapidly once it is in the soil so applying P near the root zone will aid in reducing the runoff potential as well as provide the nutrient needed to assist in plant vigor. It is for this reason that broadcast is not recommended for application of P. A good approach is to consider banding the P directly into the soil at the root zone.

Erosion Control

As the biggest environmental risk from P is runoff into nearby lakes and streams, proper management of erosion is critical. Consider conservation tillage or strip-tillage practices to minimize erosion, and thereby P loss.

Buffer Strips

Buffer strips (an area where no manure of fertilizer is applied) will reduce the P runoff impacts to the environment. 

So now we have a Nutrient Management Plan and a few BMP's to help guide you in your decision making process. Every farm is different so some BMP's may be applicable, some not. Do you have any that should be included that you would like to share? 

As you work through your Plan and BMP's and get ready to implement them, consider taking a look at our production management suite of tools, AgFleet. There is also more information on our home page.

Coming up next will be discussions concerning tillage systems used in production agriculture.