Do Big Yields Mean Big Money? Back »

Written collaboratively by Anthony Bly, Sara Berg, and David Karki.


Do you believe the highest yields return the greatest profit? Are you managing for maximum yields? Do you attempt to manage your corn crop for the highest yields as a result of what yield contest winner’s say? Maybe you have heard that balancing soil cations are what you want to do, but you can’t afford over 500 lbs K2O/a so you go with a lower rate that is still much higher than recommended? If you have answered yes to any of these questions, you might be missing some profit!

Nutrient Management Considerations

The highest, or maximum yields do not necessarily correspond to the highest net returns. Accepting yields below the maximum in your area may be in your best interest. Let’s take a look at a replicated research project that compared nutrient application rates. This corn study in Minnehaha County compared cost-benefit ratios associated with different nutrient recommendation strategies (Table 1).

The highest yielding treatment was from the “Maximum” nutrient application strategy with 192.9 bu/a. However, the most profitable nutrient management strategy was the “N only” application, which had the lowest yield. A very close second, separated by only $0.83 net return was the university recommendations based on unbiased nutrient research calibration (SDSU Extension Fertilizer Recommendation Guide). Attempting to go after the maximum is not profitable with a loss of -$129.21 compared with “university” recommendations. The “What if?” treatment uses the yield from the “Maximum” treatment only to compare a “what if” scenario for nutrient rates more in line with what producers are doing in the field, which is $104.30/a nutrient cost; this “What if?” treatment still lost -$67.82 compared with the “university” recommendations.

The Bottom Line

The secret to profitable nutrient application is knowing how much to apply based on accurate field yield history and soil test knowledge. Nutrient rates should be based on sound university recommendations which do not include nutrient applications based on crop nutrient removal. In this research, soil test P, K, and Zn were in the “Very High” (VH) soil test category and therefore required no additional nutrient application. As our agricultural systems become more tested by economic bottom lines and environmental concerns, the importance of strict management of our nutrient resources cannot be overstated.


Table 1. Nutrient management strategy comparison for corn. Minnehaha County SD, 2017.
Nutrient
Strategy
Nutrient
Rates
Grain
Yield
Fertilizer
costA
Net Return
to NutrientsB
Adjusted Gross
for FertilizerC
  lbs/a N-P2O5-K2O-S-Zn bu/a $/a $/a $/a
N only 100-0-0-0-0 159.2 38.00 na 439.48
UniversityD 160-0-0-15-0 181.0 66.40 -0.83 438.65
MaximumE 300-80-300-25-10 192.9 232.20 -130.04 309.44
What if?F 160-40-60-20-2.5 192.9 104.30 -68.65 370.83

A N=$0.38, P2O5=$0.37, K2O=$0.28, S=$0.376, Zn=$1.00 (base on December 2017 cost)

B compared to N only nutrient strategy.

C Grain Yield X $3.00/bu – fertilizer cost

D University recommendations based on EC-750 and 175 bu/a yield goal.

E Non-limiting N, crop removal P and build, base cation approach K, high S and Zn.

F University N, crop removal P, build soil K, insurance S and Zn.

Soil test results: Organic Matter = 4.1%, 90.6 lbs nitrate-N (0-2ft depth), Olsen P = 22.5 ppm (VH), soil test K = 164, pH = 6.2, SO4-S = 22.4 lbs/a, Zn = 2.92 ppm (VH)

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