In talking with growers this winter, some of them have voiced concerns about planning for the 2021 cropping season with rising fertilizer prices. This is a good time to go over a few fundamentals when it comes to planning fertilizer purchases.

Here are five tips that I would suggest growers consider if they are looking to reduce fertilizer costs this upcoming spring:

1. Prioritize macronutrients over micronutrients. Cutting fertilizer application rates across the board is not the only way to trim costs. For corn, the nutrient that is going to provide the greatest return on investment is nitrogen, as it is generally most limiting to the crop. The need for phosphorus and potassium for a crop is highly dependent on management philosophy. The soil can contain enough of each nutrient that it may be easier to cut down on phosphorus and potassium than nitrogen or sulfur, which readily leach from the soil in their crop-available forms.

I also continue to see advertisements for micronutrients claiming that they are so cheap that you cannot afford not to apply them. The simple fact is that you cannot afford to cut nutrient applications such as N, P, K and S for the sake of applying micronutrients that likely will not have a high return on investment. The $5 per acre you may spend on micronutrients would be better spent on nutrients that form the foundation of your nutrient management program.

2. Pay attention to your P and K soil tests. Soil testing is the best way to target your nutrient needs, trimming costs where P and K are not needed and applying these nutrients where they are. There is always the concern that P and K application rates that are less than what was removed by the crop will result in a drop in soil tests over time. Our recent research has shown that applying as low as 40% of crop removal of P and K has been able to keep the soil test near optimal levels, while not reducing crop yield in the short term.

Will this strategy result in lost yield potential in the long-term? That is possible if the soil test drops to levels where higher rates of fertilizer are needed to maximize yield, and the same rate of fertilizer is applied year after year without testing the soil.

One thing I stress to growers is that with P and K, there is more flexibility in what rates are applied in the short term. If the nutrients are needed for the crop, that application is better than nothing. If you are managing fertilizer to the point where you are applying only what the crop needs, more frequent soil testing is needed to monitor soil tests to catch situations where soil tests decline and more fertilizer may be needed.

3. Make sure you’re accounting for all nutrients you are applying. Remember, some of the fertilizer products you apply contain multiple nutrients. Make sure you are crediting nutrients in any starter fertilizer you are planning to apply. Particularly, credit P applied against your target P application for a field, as well as any other nutrients applied in the starter.

If you applied MAP or DAP in the fall, be sure to credit the N in those products. There is no simple answer as to how best to credit N from fall applications of MAP or DAP. The earlier they were applied in the fall, the more likely it is that the ammonium will convert to nitrate, which may be lost before it can be taken up by the crop in the spring.

4. Fertilizer enhancers and soil amendments can be risky investments. If you are concerned about what you are spending on your overall fertilizer program, cutting costs on products that have not been proven to consistently increase yield is a good place to start. There are several products on the market that claim to increase nutrient availability — which are tempting, as they can potentially increase the benefit of the fertilizer you are applying. The simple fact is that in our years of research, we have never seen one of these products consistently increase yield. Even nitrification or urease inhibitors do not return the cost of your investment 100% of the time.

I will admit that every once in a while, we catch lightning in a bottle, and we get a yield increase from a particular product we are testing. If yield is increased at one in five locations, or in one of three years, is that enough to warrant widespread use of a product? Consider that even fertilizer is not 100% effective at increasing yield in a low-testing soil.

What you need to decide is the probability you are willing to accept that something may not work. The issue is that, in many cases, the probability that no response occurred is not given, so it is hard to determine the overall effectiveness of a fertilizer enhancer or soil amendment. It is best to invest your money in what you are certain will pay you back and avoid what likely will not.

5. Stay up to date on the latest University of Minnesota research and use our web pages and tools. Subscribing to our Minnesota Crop News blog is the best way to keep up with the most recent findings from U-M crop research, as well as the online and in-person events we offer throughout the year. The Extension website also features comprehensive guides on everything you need to know about nutrient management and crop production, including our recently updated corn and soybean fertilizer guides. The corn nitrogen rate calculator is one of the most popular data-driven tools we have to help corn growers maximize yields and cut input costs. The Nutrient Management Podcast is a great place to hear monthly in-depth discussions with researchers on timely topics. You can subscribe to the podcast on iTunes or Stitcher. And our YouTube channel features short videos highlighting important research and recommendations.

Kaiser in an Extension nutrient management specialist with the University of Minnesota. University research is sponsored in part by the Agricultural Fertilizer Research and Education Council.