How 4R Nutrient Stewardship can help Minnesota farmers

By: Lindsay Pease, Extension nutrient management specialist, Northwest Research and Outreach Center

If you haven’t heard about the 4Rs, this is the time to jump on board. The 4R Nutrient Stewardship concept is centered on the idea that the goal of soil fertility to apply the right source of nutrient, at the right rate, at the right time, and in the right place.

The 4R framework is more of a soil fertility philosophy than a prescription. The exact soil fertility management plan will vary from farm to farm. But the overall goal is the same. If you are applying fertilizer in the most efficient, economical way possible for your farm, then both your farm and your community benefit.

Soil is not as good at holding nutrients as we would like to believe. Over-time, the ‘build-and-maintain’ approach to fertilizer management leads to nutrients leaking off the field during heavy rainfall events in surface runoff or tile drainage discharge. As we have seen around the country, excess nutrients in waterways often end up with people pointing fingers at farms. So instead of waiting for the finger-pointing, the 4R framework encourages farmers to take a more active approach that is win-win. By optimizing fertilizer application, you can reduce fertilizer costs while maintaining yield and minimizing fertilizer loss to the environment.

Here are each of the 4Rs in a little more detail:

Right Source

Consider different nutrient sources when making a soil fertility plan. Both organic (manure) and inorganic (commercial) fertilizers can be great sources of nutrients for your crop, but not all sources provide the same benefits. What works best will depend on your soil, weather, and crop rotation. You can also combine sources to get the right balance of nutrients. For example, if you apply manure, consider running a nutrient analysis to see if you need to supplement it with fertilizer containing nitrogen or micronutrients to better meet crop needs.

Right Rate

Match fertilizer rate to crop nutritional requirements and account for the nutrients you already have in the soil when deciding on a fertilizer rate. Soil testing is a critical piece of optimizing nutrient application rate. With Minnesota’s short window for post-harvest fieldwork, fitting in soil sampling can be a real challenge. But it can pay off in the long run, particularly if it allows you to apply slightly lower fertilizer rates each year than you would otherwise.

Right Time

Apply nutrients when soil and weather conditions will be most favorable to keeping them in the field. When soil temperatures are below 50 degrees, biological nitrogen cycling is reduced, so your nutrients are more likely to stay put until the spring thaw. If you can avoid fall application altogether and apply nutrients as close to planting as possible, then there is less opportunity for those nutrients to be lost due to an unseasonably warm winter or an exceptionally wet spring. In Minnesota, the potential for warm-weather nitrogen loss is a main reason why we do not recommend applying urea in the fall.

Right Place

Place nutrients where they have the best chance to be picked up by the crop. Nitrogen moves readily into air, water, and other living things (like weeds or microbes), so it needs to be placed carefully and with consideration of weather and soil conditions to keep it in the field. Phosphorus does not move as readily into deeper portions of the soil profile, so doing some form of subsurface placement can reduce application rates up to 50% without sacrificing yield.

4R Nutrient Stewardship Certification Program

Minnesota Crop Production Retailers recently launched a 4R Nutrient Stewardship Certification Program. This voluntary program provides fertilizer suppliers with an industry-backed certification that shows they are committed to:

• Increasing grower profitability by optimizing fertilizer efficiency
• Strengthening the relationships between nutrient service providers and grower customers 
• Achieving higher crop yields 
• Preserving natural ecosystems by growing more on less land 
• Supporting state and nation-wide efforts to reduce nutrient runoff 
• Helping safeguard drinking water supplies 

The UMN Extension Nutrient Management Team is constantly evaluating and adapting the 4R concept for the unique combination of landscape, crops, and climate that we have here in Minnesota. Extension nitrogen management specialist Fabian Fernandez has been working with the Nutri-Net Project to determine the best nitrogen best management practices for Minnesota. In the coming years, I will be leading a multi-year, cross-border project to evaluate how to adapt 4R Phosphorus Management for the cold-climate agricultural operations we have here in the Northern Great Plains.

Stay up-to-date on the project’s progress by subscribing to the Minnesota Crop News email newsletter and follow me on Twitter @LPeaseUMN.

This blog post was originally published in November 2020. 

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Support for Minnesota Crop News nutrient management blog posts is provided in part by the Agricultural Fertilizer Research & Education Council (AFREC).