Soil Fertility
There are a lot of moving pieces when it comes to managing soil fertility including soil testing, interpreting soil test results to make fertilizer recommendations, understanding different crop nutrients needs, accounting for crop nutrient removal, knowing how to manage different fertilize sources, and being able to identify crop nutrient deficiencies. Find more information on soil fertility management for crop production in Iowa.
Timely Insights on Soil Fertility
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June 17, 2026Content Author
Photo by: John Sawyer, ISU Extension Retired
It's a question that arrives in our inboxes every spring without fail: "It's been raining — have I lost nitrogen, and do I need to apply more?" This year is no exception. With a highly variable spring precipitation pattern across Iowa (see map below) and corn now approaching or past the critical V6 growth stage, many producers are seeing yellowing in their fields and wondering what to do next.
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May 29, 2026Content Author
Residual soil nitrogen levels last year were relatively high and extremely variable from field to field. That means the Late Spring Nitrate Test (LSNT) can generate a large return on investment for in-season nitrogen decision-making this year. For those making in-season nitrogen applications, there may be significant opportunity for savings on fertilizer inputs.
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April 24, 2026Content Author
Residual soil nitrogen levels may be higher than average heading into 2026 due to the relatively warm winter, meaning some fields may need less sidedress N fertilizer than in a typical year. The Late Spring Nitrate Test (LSNT) can be used to reduce uncertainty in N fertilizer needs, lowering the risk of both under and over application.
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March 26, 2026Authors
This spring began with higher and uncertain phosphorus (P) and potassium (K) fertilizer prices, with a higher increase for P fertilizers. Fortunately, corn and soybean grain prices began increasing in February and expectations are for further increases, mainly for corn (Chad Hart - Ag Market Outlook). Although many producers already applied the phosphorus (P) and potassium (K) needs for 2026 last fall, others will apply them this spring and are considering reducing planned rates due to lower expected economic benefits from fertilization. However, reducing P and K rates across all conditions is not a good management decision.
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March 24, 2026Content Author
Optimum nitrogen (N) fertilizer rates for corn vary widely from field to field and from year to year. One reason is that the amount of nitrogen left in the soil after harvest is never the same. Measuring residual soil inorganic nitrogen—ammonium (NH₄⁺) and nitrate (NO₃⁻)—can help indicate whether fertilizer needs for the upcoming crop may be higher or lower than usual.
