The 2019 growing season provided many challenges to farmers. Above-average precipitation coupled with a cooler-than-normal spring led to many acres being planted late or not planted at all. Harvest this fall also had many challenges to overcome. Throughout it all though, nutrient management remained a top priority for farmers.

Iowa State University along with USDA’s Natural Resources Conservation Service encourages farmers to practice the 4R’s of Nutrient Management. The 4R’s provide a framework for farmers to achieve cropping system goals, such as increased production, increased farmer profitability, protection for the environment, and improved sustainability for agriculture.

By implementing these practices, farmers can optimize the nutrients they apply to maximize plant uptake and minimize field losses. These practices assist in keeping nutrients in the plant root zone and available when the crop needs them during most of the growing season.

Defining 4R approach

The breakdown of the 4R’s in order follows:

Right source. Selecting the right fertilizer source means matching the right type of fertilizer with the soil properties as well as the crop’s needs. One way to select the right fertilizer is to use a fertilizer source that has a guaranteed or known analysis. Using controlled, slow release, or stabilized nitrogen blends should also be considered. If you apply secondary nutrients and micronutrients, do that based on soil and tissue test results.

It’s especially important to address phosphorus and potassium needs. Although nitrogen is thought of as the most important nutrient for crops, nitrogen can be wasted if phosphorus and potassium needs aren’t met.

Right rate. The right fertilizer rate means matching application rates with crop needs. This may mean coming up with a fertilizer plan to account for all the inputs and harvest removal. Using soil samples to help determine fertilizer application rates is also recommended. If available, using a variable-rate application of fertilizer can also help match fertilizer amounts to crop needs. Only applying what the crop needs for optimal production can save both time and money.

Right time. This means making nutrients available when crops need them. It may mean split-applying nutrients more than once to increase their availability while decreasing the risk of runoff or leaching. It may also mean selecting controlled release fertilizers and nitrification inhibitors to help control nutrient availability.

Generally, it’s recommended to apply nutrients in the spring, compared to fall, to reduce potential nutrient runoff or leaching. If nitrogen is applied in the fall, ISU recommends waiting until soil temperatures are consistently below 50 degrees F at a 4-inch soil depth.

Right place. Selecting the right place means keeping nutrients where crops can use them. Different types of crops, different types of cropping systems, and even different types of soils may dictate where the best placement of nutrients is in the soil. Using precision guidance technology, incorporating broadcast-applied fertilizers and injecting fertilizers are some methods to help keep nutrients in place and increase their overall efficiency.

Properly managed fertilizer and nutrient programs help support cropping systems that provide environmental, economic and social benefits. This may help encourage discussions between farmers and advisers about improving fertilizer management practices across more acres.

On the other hand, poorly managed fertilizer programs can decrease the overall profitability, as well as increase nutrient losses that may affect our soil and water. Other agronomic and conservation practices such as reduced tillage and the use of cover crops also play a role in nutrient management. For more information, visit 4rplus.org.

Michel is an ISU Extension field agronomist covering southeast Iowa. Contact him at [email protected].