High yields have long been the measure of success in corn and soybean country, but bigger harvests also remove more nutrients from the soil. When tight margins limit fertilizer spending, replacing those nutrients can be a challenge.
That could be what the latest report from The Fertilizer Institute (TFI), based on more than 10 million soil samples across the United States and Canada, is simply reinforcing. TFI found that 45% of samples tested deficient in phosphorus (P) and 41% fell below adequate potassium (K) levels.
That finding raises a practical question, says Tryston Beyrer, field solutions agronomist with Mosaic.
“Are we fertilizing appropriately to meet our crop demands and needs?” he asks.
For farmers watching input costs and struggling to achieve ROI with corn and soybeans, answering that question sooner than later can help determine where adjustments might need to be made by next season.
Consider Crop Nutrient Removal Levels
Phosphorus levels have been trending downward in many areas. Beyrer notes that a three-parts-per-million (ppm) drop in soil phosphorus over five years might sound minor. But even small changes can add up over time, particularly in fields that are already low in phosphorus.
“The way that we rectify this is, No. 1, to understand what our crop nutrient removal is,” Beyrer says.
Farmers can start with their yield records. Higher yields generally mean more nutrients leave the field, so a fertilizer program that worked when yields were lower may need another look as production levels increase.
Comparing estimated nutrient removal with fertilizer application records can help growers see whether they’re replacing what the crop takes out or gradually using up soil reserves. Over time, that information can help them make adjustments before declining fertility becomes a bigger concern.
Potassium Deserves a Fresh Look
Potassium is another nutrient showing deficiencies. Although many soils have historically supplied adequate amounts, the TFI findings suggest that’s not the case everywhere.
“I think we’re at this tipping point where we’ve utilized much of our reserves of our potassium,” Beyrer says.
For growers, the next step is figuring out where potassium levels are falling short and which fields need attention first. Soil test results can help identify those areas and guide decisions about maintaining or improving fertility.
Where fertility is already adequate, maintaining that level may be the best use of fertilizer dollars. Where levels are declining, the goal is to keep the problem from growing while weighing the cost of correction against the potential ROI.
Don’t Overlook Other Nutrients
While phosphorus and potassium get much of the attention with the TFI report, Beyrer encourages farmers to look at the report’s findings for sulfur, chloride and micronutrients such as zinc, too. These nutrients can become yield-limiting in particular soils and regions, even when the major nutrients aren’t a concern.
Make Every Fertilizer Dollar Count
The TFI report, updated every five years, gives farmers a broad view of nutrient trends across North America. But regional averages can only tell them so much about what’s happening on their own farms.
Even within the same field, fertility levels often vary, as farmers know. One area may have adequate phosphorus and potassium, while another needs more attention.
That’s where variable-rate technology can help. By adjusting application rates to match the needs of different management zones, farmers can direct more fertilizer to areas that need it and avoid unnecessary applications where nutrient levels are already adequate.
As Beyrer explains, the goal isn’t simply to spend more on fertilizer. It’s to put nutrients where they have the best chance of paying their way.
A more targeted approach can help prioritize limited budgets, address deficiencies and maintain fertility in areas that are already in good shape.
“Utilize soil testing as a tool to help make informed decisions,” Beyrer advises, “and prevent nutrient deficiencies from limiting production in the future.”
TFI members can request a complimentary copy of the Summary Update by emailing store@tfi.org for details.
Also, watch Beyrer provide more details on the RealAgriculture Soil School, at the link below.
