Eagle Ag Consulting

"Revenue Based Agronomy"

Improving Fertilizer ROI

 Winter Crop Days 2022 discussed many topics, soil scientist Jeff Vetch, U of MN Waseca, presented on some ideas to consider in 2022 if you haven’t already gotten your fertilizer purchased.  To start, for the past 20 years the nitrogen recommendations have been based off a fertilizer price to corn price ratio.  After the introduction of genetically protected corn hybrids in the late 90’s researchers found a disconnect from final yields and yield goals.  Typically, we see a ratio of about .10 ($.40 N & $4 corn) but we currently sit at over $1 per pound N and $5.50 corn giving us a .20 ratio!  Research on yield response applied to the economics says your rate today should be 40-50 lbs per acre less than normal.  Todays N rate for the state of MN is 142 lbs per acre for corn on corn (normally 180+) and 105 lbs for corn after soybeans.  While this is the economic optimal, is does provide less final yield and a gross of nearly $80 less.  Check out the graph to the right.  Minnesota has recently updated their K (potassium) recs and have raised the rates in many cases along with moving the critical level for response in fine or medium textured soils from 150 ppm to 200 ppm.  On sandy soils they lowered the critical rates as the soil test (ammonium acetate) we use is underestimating what is available.  The final major cost is from P-Phosphorus.  This is the one to really focus on says Vetch.  The chances of a yield increase are quite low if your soil test is medium or above.  If you ever dipped into the soil bank on your farm, this would be the time.  Vetch encourages you to take a hard look at soil tests and break out fields into rented and owned-you may want to manage them slightly differently.  If you have a soil test in the medium category or above, research has shown that when you do get a yield increase, it is relatively small.  We can break down each test value to a specific percent but let’s just say the response is usually 2-5% for corn and less for soybeans.  Think twice before buying much P this spring.  

Updated: March 14, 2022 — 9:28 pm
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