From precision ag to nutrient balance, Missouri soybean farmers are finding smarter ways to feed their fields — and not their runoff.
Missouri soybean farmers know that adequate soil fertility is critical to achieve good yields. But as input costs rise and environmental scrutiny increases, growers are turning to more precise strategies to balance crop needs with efficient resource use.
Building the Basics of Nutrient Management
Successful fertility programs start with soil testing and a clear understanding of yield goals.
University of Missouri assistant professor, soybean farming systems, Andre Froes de Borja Reis, said many Missouri fields still benefit from a back-to-basics approach.
“Sampling is something we can’t skip. There’s no substitute for knowing what’s actually in your soil,” he says. “We see variability across fields and over time. Having an accurate understanding of what the soil can provide directly affects the fertilizer rate to be applied and therefore the return on investments.”
Missouri’s diverse soils, from loess hills to claypan landscapes, present a challenge for blanket applications. He emphasized the need to adjust fertility plans not just by region but by field and sometimes by zone.
Precision Agriculture Levels the Playing Field
Technology now makes it easier to manage that variability. Whether through yield maps, grid soil sampling, or NDVI imagery, growers can fine-tune nutrient applications to meet crop needs more accurately.
“Precision ag is an important tool to be considered,” Froes de Borja Reis says. “It’s about gathering better data so we can make better decisions — especially when it comes to phosphorus and potassium. However, if gridded sampling and variable-rate prescriptions are not available, conventional sampling and a fixed-rate application per field still offer valuable benefits”. A fixed-rate recommendation based on soil analysis is still preferable to a blanket application
Many growers are using variable-rate technology to apply nutrients only where they’re needed, which not only saves money but reduces the risk of nutrient runoff. For phosphorus (P), potassium (K) and sulfur management in soybean variable rate has also shown positive results.
Avoiding Fertility Pitfalls
Even with the best tools, mistakes happen.
Froes de Borja Reis says a common pitfall is focusing solely on a few nutrients — primarily macronutrients like phosphorus (P) and potassium (K) — while overlooking the management of micronutrients and other essential macronutrients such as sulfur (S) and magnesium (Mg).
When developing a nutrient management strategy, it is important to consider not only the availability of all nutrients in the soil but also the relationships between them. Often, an excess of one nutrient can inhibit the absorption of another, and the yield response to any nutrient application will always be limited by the level of the most deficient nutrient. In other words, the response to potassium (K) can be limited if the soil is deficient in boron (B). It is always advisable to consult an agronomist.
On the other hand, nitrogen is very unlikely to be a concern. Soybean can fix its own nitrogen from the atmosphere and response to N fertilization is rare.
Froes de Borja Reis encourages growers to treat fertility as part of an overall system —not an isolated decision.
“If we’re pushing yield, we have to look at the whole picture—crop rotation, organic matter, timing, placement, and weather risk,” he says. “There’s no silver bullet, but there are a lot of smart moves we can make.”
This article is funded in part by the United Soybean Board.