Strategic Farming: Let's talk crops highlighted nitrogen management and economics

 Liz Stahl, Extension educator - crops

The 6th season of “Strategic Farming: Let’s Talk Crops!” launched January 8th with a discussion on nitrogen management given current crop and input economics. Dr. Fabian Fernandez, Extension nutrient management specialist and Brad Carlson, Extension educator – water quality, joined Extension Educator - Crops, Dave Nicolai, for a discussion around this critical nutrient.

Looking back at 2024

2024 was a year of extremes. The season initially started out dry and farmers were hoping for an early planting season. Then it rained, rained, and rained some more, making timely planting elusive for many. Excessive precipitation resulted in widespread N losses. Drainage issues were marked by yellowed corn in many fields. Although yields were respectable and even decent in some fields, yields were significantly lower than hoped for in others. Greater N mineralization than normal early in the season due to warmer than usual temperatures followed by intense rain impacted the amount of N that was available for the corn crop later in the season. In-season rescue N applications helped in some cases, but weather conditions created many challenges for N management in 2024. The year’s experiences also helped confirm some key guidelines in N management.

Fall urea applications falling short

Fernandez discussed University of MN research conducted across the state comparing applications of urea in the fall and spring. Multi-year trials showed that on average, more N was needed to reach the maximum return to N and to achieve the best yields with a fall urea application than a spring urea application. An average of 12, 16, 35 and 47 more pounds of N/ac were needed to reach the maximum return to N when urea was applied in the fall compared to in the spring at Lamberton, Morris, Waseca, and Crookston, respectively. It is also important to note that corn yield was higher when urea was applied in the spring than in the fall, with the advantage ranging from an average of 5 bu/ac at Morris to 13 bu/ac at Lamberton for spring application over fall application. This means that yields were greater with a lower N rate when urea was applied in the spring than in the fall. Additional trials indicate that anhydrous ammonia is the most reliable source of N when N is applied in the fall.

Figure 1. U of MN Research compared the effect of timing of urea application (fall versus spring) at 4 locations (Crookston, Lamberton, Morris, and Waseca) on the maximum return to nitrogen (MRTN) rate and yield.

Spring-applied ESN can help

How has urea performed compared to ESN (Environmentally Smart Nitrogen), a controlled-release product, when applied in the spring? With ESN, each urea granule is coated with a water-permeable polymer coating. As the soil warms, more N is released into the soil. ESN applied preplant has performed fairly well in wet conditions. In 2024, where there was an extreme amount of moisture in June, there were likely still some losses of N with ESN. ESN did help reduce N losses, though, compared to urea. Fernandez recommends ESN be applied either preplant or very early sidedress (before corn reaches the V2 stage) to reduce the risk of there not being enough time for N release before the crop needs it. More details on ESN can be found in the article “Are controlled-release nitrogen fertilizer products worth the cost?”

Sidedressing N most likely to pay only in special situations

Although the concept of “spoon-feeding” the crop has been discussed and promoted by some, the bottom line is that the nutrient just needs to be there when the crop needs it, otherwise yield can be hurt. Applying N twice means you double your application costs too. In 49 site years of research conducted across the Midwest, in most cases no advantage was seen when N was applied in a split application vs in a single application. Where an advantage was found to applying N in a split application, there tended to be a specific situation such as the field was undrained, the soils were sandy, or conditions were very wet. In wet years, for example, split applications resulted in less N being needed.

Research trials also highlight the impacts of soil drainage. In U of MN research conducted from 2014 to 2019, regardless of timing, undrained soils needed an average of 28 lb N/acre more than drained soils to optimize yield. In drained soils, preplant applications were adequate, and less N was required to optimize yield compared to a split application. In wet years, drained soils were more productive and profitable than undrained soils. Split applications can be better, however, for undrained soils.

Research is also showing that splitting your N application doesn’t improve crop intake or increase the amount of N that will be available for the next crop.

The most profitable farms have lower fertilizer costs

Using FINBIN data (anonymous data generated from farm financial reports from the MN farm business management program), Carlson found that the top 20% of farms in profitability spent about 25% less per acre on fertilizer than the bottom 20% of farms. From 2016 to 2023, this amount varied from 15 to 33%. Since the data is anonymous, one can’t look at the farmer’s specific practices to see what might be driving the difference, but several management practices are likely involved.

Applying too high of a nitrogen fertilizer rate is one likely factor. U of MN fertilizer guidelines are based on hundreds of research trials, conducted over many years and sites. If your application rates are greatly above these, do you have a valid reason why?

Consider that N rates may be higher to mask bad application choices (e.g., applying urea in the fall, applying N when it is too warm). There are also many products on the market that claim to be “more available” or provide some other advantage. Unfortunately, research has not clearly shown these products to work consistently, and they are an added expense. Evaluate if variable rate technologies, which can increase your expenses as well, are helping yield or not. A more detailed discussion can be found in the article “Are you overspending on fertilizer?”

Questions on tillage, manure and more

Participant questioned the impact of tillage system, particularly strip-tillage, on fertilizer rates. Fernandez commented that strip-tillage does not require less nutrients than other systems. Many questions also centered around fall manure applications. We are seeing warmer falls, which raises concerns over the potential for N losses. It is recommended to follow the recommendations for commercial fertilizer, where applications of N in the fall (where allowed) should be delayed until soil temperatures stabilize below 50F, as much as possible.

Listen to recordings of this program at: z.umn.edu/strategic-farming.

Join us next week!

The University of Minnesota’s Strategic Farming: Let’s talk crops! webinar series, offered Wednesday mornings through March, features discussions with the experts to provide up-to-date, research-based information to help farmers and ag professionals optimize crop management strategies. Next week’s session will be on “Targeted herbicide spray technology” with Dr. Rodrigo Werle, Extension cropping systems weed scientist, with University of Wisconsin-Madison. For more information and to register, visit z.umn.edu/strategic-farming.

Thanks to the Soybean Research and Promotion Council and the Corn Research and Promotion Council for their generous support of this program.