Nitrogen is essential for crop growth, but essential does not mean unlimited. One of the most useful challenges in John Kempf’s discussion is the suggestion that the crop with the most nitrogen is not always the crop with the greatest yield.
Kempf uses the phrase yield drag to describe situations where excessive nitrogen—especially nitrate-dominant nutrition—appears to keep plants in a strongly vegetative state or consumes water and energy that could otherwise support reproductive growth.
The management goal is to supply nitrogen in the form and at the time that support yield and quality. Maximum uptake is a different measure.
Listen to this part of the conversation #
Suggested section: 6:33–10:21. The player begins at 6:33; pause when you reach the end of the suggested section.
Listen for why Kempf describes excess nitrogen as a possible source of yield drag, and how he separates crop response from the assumption that more nitrogen always produces more yield.
Originally published on 3 April 2026 as Podcast Extra: Adjusting Nitrogen Management with John Kempf and MSHC. Full episode: 1:00:54. Audio is streamed from Libsyn.
Look for response, not just deficiency #
Conventional scouting is often organised around shortage: pale leaves, restricted growth or a tissue result below a reference range. An optimisation approach also watches for possible excess or imbalance.
Useful observations may include:
- lush growth that does not translate into yield;
- delayed maturity;
- weak stems or lodging;
- high water demand;
- nitrate accumulation relative to other nitrogen forms;
- diminishing yield response from additional applications.
None of these observations proves that nitrogen is the cause. They are prompts for comparison and measurement.
Build a rate-response test #
A practical trial can compare the standard program with one or more carefully reduced or retimed treatments. Keep a properly replicated control, record all nitrogen sources—including manure and biological products—and measure both yield and economic return.
The financial comparison should include product, application and extra-pass costs. A lower-input treatment is not automatically better if it reduces revenue, and a high-yield treatment is not automatically better if its added yield costs more than it returns.
A transition, not a stunt #
Kempf presents nitrogen reduction as a staged transition. Biological activity, soil carbon, fertilizer history, water availability and management capability can all affect how quickly purchased nitrogen can be reduced. Reduce the rate in measured steps, checking whether nitrogen-use efficiency, yield and quality improve or decline.
Questions to take into the field #
- Where does added nitrogen stop producing a reliable yield or quality response?
- Could lush growth, delayed maturity or lodging be signalling excess or imbalance?
- Are all nitrogen sources—including manure and biological products—being counted?
- What is the full cost of each treatment once product and application are included?
- What is the smallest safe rate or timing comparison that can be replicated?
What this evidence can—and cannot—show #
Yield penalties from excessive nitrogen are agronomically plausible and can occur, but the threshold is crop- and site-specific. Kempf’s explanation in this webinar blends plant-nutrition principles with field observation. Use replicated trials and local agronomic advice before making large reductions.
The practical takeaway #
The best nitrogen rate is not the highest rate the crop can absorb; it is the program that produces the strongest agronomic and economic response.
Further reading #
- Original recording and episode notes
- Minnesota Soil Health Coalition
- Advancing Eco Agriculture: Regenerative Nitrogen Management
Source: John Kempf, Regenerative Agriculture Podcast, Podcast Extra: Adjusting Nitrogen Management with John Kempf and MSHC, published 3 April 2026.
Evidence note: The possibility of yield penalties from excessive nitrogen is agronomically plausible, but the threshold is crop- and site-specific. Kempf’s explanation combines plant-nutrition principles with consulting experience and grower observations; large reductions require replicated local testing. The podcast is produced by Advancing Eco Agriculture, and AEA products mentioned in the wider recording should be understood in that commercial context.