PMN Webinar--Reducing Nutrient Loss From Farmland
The Plant Management Network (PMN) has posted a webinar in its Focus on Soybean series entitled “Reducing Nutrient Loss from Farmland” presented by Dr. Fabián Fernández, Assistant Professor in the Dept. Of Soil, Water, and Climate at the University of Minnesota. Dr. Fernández discusses the management of nitrogen (N) and phosphorus (P) fertilizer inputs in order to maximize productivity and environmental protection. Specific points that pertain to most US production sites are highlighted below.
- Both N & P can have negative environmental effects when they enter surface waters (N & P), groundwater (N as nitrate leaching), or the atmosphere (N as N oxide emissions).
- Nitrate moves mostly with water, while phosphorus moves mostly with soil.
- Addition of both fertilizer elements should be made according to soil test values and fertilizer guidelines. Determining how much N is needed for corn grown in rotation with soybean can be determined with tools such as the Maximum Return to Nitrogen (MRTN) calculator (for the Midwestern US states).
- Adding fertilizer N to a site cropped to soybean is rarely beneficial. Click here for a detailed treatment of this subject.
- Rotating soybean with corn or split applications of N to corn result in lower nitrous oxide emissions into the atmosphere.
- Applying higher-than-needed N rates to corn leads to higher residual nitrate levels in soil.
- Best management practices have been developed to prevent losses of N that result from applying N in excess of that needed for optimum corn yield.
- Nitrate leaching can still occur in the soybean year of a corn–soybean rotation.
- Phosphorus fertilizer that is incorporated into soil will drastically reduce the P lost in runoff compared to that lost in runoff following surface-application of P.
- Phosphorus fertilizer that is banded in the row will create high P levels in the banded zone, but will not fertilize the rest of the soil. This will affect soil sampling protocol for P.
- Subsurface banding of P fertilizer will maintain soil P levels similar to broadcast applications, but will lower levels of P in the soil surface and thus lower the amount of P that is subject to loss in water runoff.
Even though this presentation is designed to help consultants and growers in the North Central US, many of its tenets are also applicable for Midsouth corn and soybean production systems. Producers are encouraged to view this webcast for information that can be used to enhance fertilizer management for and reduce nutrient loss from these systems.
Composed by Larry G. Heatherly, July 2015, larryheatherly@bellsouth.net