2024 December Stewardship Advocate
Iowa Corn has collaborated for several years with Ron Lenth, Program Coordinator for Iowa State University (ISU) Extension and Outreach for Bremer County. Mr. Lenth penned the article below to report on his research in Bremer County.
Bremer County Iowa has very fertile, but heavy soils that need to utilize tile drainage to produce abundant crop yields. Weather conditions can heavily influence the flow of tile water into area streams which enter the nearby Cedar and Wapsipinicon Rivers and then empty into the Mississippi.
“I was raised on our family farm in Clayton County with a conservation mindset and started with ISU Extension here in late 2009. Seeing the emerging nutrient management issues, especially with nitrates, I found very limited data on our stream water quality. Here was an opportunity to work with area farmers and partners on this issue to benefit all and the environment,” says Ron.
Partnerships Working Together
Projects that have been vital in this effort include 14 years of routine Bremer County stream sampling for nutrients and bacteria, plus fall cornstalk nitrate sampling for area farmers. Over the years key partners have provided funding and support. These partners include the Bremer Farm Bureau, the County Board of Supervisors and ISU. The past few years, Iowa Corn has sponsored the fall cornstalk nitrate testing program, and we are grateful for that funding. We have worked with 14-26 farmers annually collecting fall field samples to test for residual nitrates. Results were shared with area farmers at field days and an open house with Iowa Corn and others in December.
2024: A Year of Extremes
Despite two consecutive years of drought in 2022 and 2023, Bremer County corn yields averaged 225 bushels per acre in 2022 and 203 bushels per acre in 2023, which is a testimony to fertile soils, high performing genetics and outstanding corn management by farmers. With those two years in the background, we wondered what 2024 would bring and what stalk nitrate levels would be after such a variable growing season. This is what occurred in 2024 in Bremer County:
- Record rainfall during May and June.
- A dry summer and September set a record for low rainfall.
- It is too early to tell what the average corn yield in the county was but it’s safe to say yields were variable due to planting dates, replanting and when growing season rains occurred.
- In 2024, corn stalk nitrate levels were the lowest in our 14 years of testing stalks (411 parts per million). See table 1.
- In most years, we average 1200 – 2000 ppm. Several universities (Iowa State, Nebraska and Minnesota) have published that the optimum nitrate are 700 – 2,000 ppm, so in 2024, we were far below the optimum levels.
Year | Average Stalk Nitrate Level (ppm) | Number of Samples Taken |
2024 | 411 | 46 |
2023 | 1805 | 46 |
2022 | 1442 | 61 |
2021 | 1469 | 67 |
Economic Optimum Level | 700-2000 |
Table 1. Average stalk nitrate levels in 2021-2024 and economic optimum range.
The optimum concentration of nitrate in the lower stalk is 700 ppm to 2000 ppm. The marginal range is 250 ppm to 700 ppm. A test result below 250 ppm would fall in the low range. Heavy pre-plant or at planting applications of nitrogen could potentially cause low stalk nitrate levels. In the same vein, too much unneeded nitrogen applied late would likely move stalk nitrate levels into the excessive category, which would be above 2000 ppm.
In a normal drought year, we would expect to see higher fall cornstalk nitrate numbers, but this year was different due to weather related issues and nutrient uptake.
Observations and Recommendations
2024 was a season of extreme weather, especially in how much and when rain events occurred (spring) and did not occur (summer and fall).
- It appears that those plants short on nitrogen during the summer drew heavily from the plant itself.
- Split applying, ide dressing and using nitrogen stabilizers made a positive difference during the growing season.
- When conducting stalk nitrate samples, follow a standardized procedure such as the method from ISU Extension found here: Use of the End-of-Season Corn Stalk Nitrate Test.
- Stalk nitrate testing can be a good addition to a farmer’s corn fertility management program but should be done over a period of years, rather relying on a test in a single year.
- Pairing a stalk nitrate test with an end of season soil analysis can help farmers make fertility adjustments before the next season.
Every growing season is different, and Mother Nature still plays a major role.
Latest Information
Fertilizer Transportation Dashboard | Open Ag Transport Data – a new dashboard created by USDA and The Fertilizer Institute tracks everything from imports to price, including exactly how each input gets to the field.
Can You Still Bank On Carbon Opportunities?Cover Crops to the Rescue
Thinking About Reducing Tillage? Start HereIs Regenerative Agriculture Real?
Farmer to Farmer: Joe Roberts
Joe Roberts farms with his wife, Paige, and both of his parents in the Belmond and Kanawha area in Wright County. He grew up farming and took on a more active role after graduating from Iowa State in 2019. Following graduation, Joe started a crop share agreement on a portion of acres with his dad to participate directly in the operation. The Roberts follow a crop rotation of corn for two years followed by soybeans on the majority of their acres. They manage their operation in the manner that works best for their situation. Joe says, “We are always on the look-out for new technology that increases profitability, and we manage our inputs to maximize efficiency all while taking care of the land we have so it will be there for years to come”.
One way they take of their soil is through no-till and strip till. Joe says “As long as I can remember, we have had a no-till farming system for soybeans. We strip-till our corn to maximize our nitrogen efficiency. All of our nitrogen on the farm is in the liquid form, being 32% UAN. We split apply about 50% of the need for the year pre- plant when we do our strips, and the remainder comes via a side dress applications.
In addition to strip- and no-till, the Roberts use cover crops on all their acres. Joe notes, “Improving soil health and capturing nutrients have been a couple of the benefits of cover crops. We have tried a wide variety of cover crops, having just broadcast cereal rye, two varieties of clover, winter camelina, rapeseed, kale and radish this fall. We like the ability for our cover crops to overwinter so for termination we use an herbicide around the same time we plant depending on weather conditions and manpower.”
The Roberts use the ISU Nitrogen Rate Calculator to maximize their return while taking into consideration where cash prices may go for the year. They have recently added sulfur to all of their nitrogen applications. In the past, they noticed sulfur deficiencies so adding sulfur has become a standard component of their fertility program. Joe notes that starter fertilizer is the key, “We have seen the biggest production increase using an in-furrow application of a starter fertilizer (6-24-6) during planting to really jump start that growth. We meet our other nutrient needs by pulling our own soil samples following our soybean production followed by creating our own variable rate application maps so we can apply our own prescriptions as we see fit.”
Joe spreads his hybrid selection across genetic suppliers to spread the risk while also utilizing multiple modes of rootworm control to prevent resistance. They plant 96 day to 110 day hybrids but find the ideal range in the 103-108 day hybrids. They tend to follow the recommended planting population with most falling in the 34-36,000 range but are experimenting with variable rate planting prescriptions to customize the planting rate across the field.
Like much of the state, Joe faced the challenge of too much moisture this spring, saying, “We saw many of our intended plans for the year get altered based upon what fields were fit to plant. We saw the majority of our corn acres go in late May and even had a couple of intended fields of corn that got switched to soybeans. We faced challenges with our cover crop taking advantage of the excess moisture and growing beyond where we had hoped for termination. An unexpected positive was the excellent weed suppression for the year due to the growth of the cover crops. Our 2024 crops were not as good as expected due to too much moisture early followed by a lack of moisture late. While we may not have a crystal ball, we are hoping for mother nature to be in our favor next year and plan to implement the same strategy for next season with a few new trials with micronutrients and biological seed additives.”
In addition to managing his family farm, Joe finds it important to give back to his industry through his involvement with Iowa Corn. He is currently serving as the First Vice President for the Iowa Corn Promotion Board and serves on the Industrial Usage and Production Committee. Nationally he is on the NCGA New Uses Action Team and also serves on the U.S. Grains Council with their Middle East, Africa, Europe, and South Asia Action Team. Joe says, “I have been an engaged member from my time in college with the collegiate club at Iowa State, Collegiate Advisory Team, county and district committees as well as Iowa Corn’s I-LEAD program to help be a voice for corn farmers and work towards increasing corn grower profitability. Without farmers telling our story of all the great things we are doing on our farms, we might have someone else writing the script so that’s why I’ve gotten involved, to help change the narrative and work towards rewriting the perception of what we do as farmers.”