Crop Nutrition

Review of Corn/Soybean Yield Trends

Robert Mullen, Ph.D.

Robert Mullen

Robert Mullen, Ph.D.

Nutrien

Director of Agronomy

To say Dr. Robert Mullen is passionate about agriculture would be an understatement. He holds a Bachelor of Science degree in ag business from Cameron University, along with a Master of Science degree in plant and soil science and a Ph.D. in soil science from Oklahoma State University. In addition, Dr. Mullen has been published in a variety of scientific and trade journals. But it’s not just his academic accomplishments that make him unique. It’s his unwavering ability to take complex data and — in simple terms — explain how it impacts a farmer’s bottom line. Dr. Mullen delivers the kind of insightful observations that can lead to a more profitable business. As a leading agronomy expert, Dr. Mullen has a goal to further educate farmers on best management practices that improve their yields and maximize their return on investment.

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Since the drought of 2012, we have experienced pretty good production for both corn and soybeans across the U.S.  The question is – just how good has it been?

The Last Three Years Put into Perspective

Figures 1 through 4 provide an illustration of corn and soybean yields and total production of both crops from 1970 to 2019.  Included within those figures is a dashed line that represents the linear trend in growth over that 49-year period.  For this analysis, we are going to focus on the deviation from the trend line for the last six years and compare it to other historical six-year periods. 

The Corn Story

Taking the cumulative deviation from the trend line for the last six years, we find a total of +33.5 bushels per acre of corn from 2014 to 2019 (Figure 1).  This means we have experienced six consecutive years of yields significantly above what we would have expected based upon the average increase in productivity (obviously excluding 2019 when we fell just below trend).  This is not the best six-year stretch we have ever experienced.  Our best six-year stretch in yield was experienced in 2004-2009 when the cumulative deviation from the trend was +37.4 bushels per acre.  Using 1970 as our starting point, we are currently adding just under 2 bushels per acre to the national average every year.   

Yield improvements have been impressive, but the other factor to consider is the number of harvested acres.  The easiest way to account for acres is to look at total production in bushels.  Corn farmers have produced a cumulative deviation from the trend line of +4.8 billion bushels over the last six years (Figure 2).  You must go back to 1977-1982 to find a six-year period that performed better (+6.4 billion bushels).  Using 1970 as our starting point, we are currently adding just under 200 million bushels to the national average every year.  Corn producers are bringing more acres into production and being more productive on those acres.  This is evidence of the improved genetics we are utilizing today as well as improved agronomic practices.

The Soybean Story

As impressive as the corn story is, the soybean story is even more remarkable.  In the last six years, soybean growers have produced yields that have resulted in +14.2 bushels per acre of cumulative deviation above the trend line (Figure 3).  That is a notable feat considering the previous best six-year period was 1970-1975, and the cumulative deviation was only +6.5 bushels per acre.  Using 1970 as our starting point, we are currently adding around 0.5 bushel per acre to the national average every year.

As you might expect, the yield levels experienced the last six years have translated to record production levels.  Soybean production from 2014-2019 experienced a cumulative deviation from the trend line of +2.9 billion bushels (Figure 4).  The closest six-year period to this record was 1977-1982 with a cumulative deviation of +1.9 billion bushels.  Using 1970 as our starting point, we are currently adding just over 50 million bushels every year to the national average.

What Does This Mean to You as a Grower?

Above trend line yields for five of the past six years translates into above average nutrient removal of potassium and phosphorus.  Just how much?  As a point of reference for your geographic area, we have provided tables that summarize the average nutrient removal based upon university publications for the major corn (Table 1) and soybean (Table 2) producing states. 

Using average coefficients for potassium (K2O) of 0.25 and phosphorus (P2O5) of 0.37 for corn (+33.5 bushel per acre), the last six years of record yields removed 9 and 12 more pounds per acre than the trend line would have predicted, respectively.  Similarly, using average coefficients for potassium (K2O) of 1.31 and phosphorus (P2O5) of 0.8 for soybean (+14.2 bushel per acre), the last six years of record yields removed 19 and 12 more pounds per acre than the trend line would have predicted, respectively. 

Did your nutrient applications keep pace with these higher yields?  If so, good work, continue to track your yields and subsequent nutrient removals moving forward (also continue paying close attention to your soil test levels). If your application rates have not kept pace and your soil test levels have begun to slip, plan to adjust your fertility strategy moving forward.  The goal is always to efficiently produce the most bushels you possibly can to maximize profit.  Ensuring adequate potassium and phosphorus availability (as well as all other nutrients) will help you towards that goal.


Figure 1.  Average corn yields (bushels per acre) in the United States from 1970 to 2019.

Figure 2.  Average corn production (bushels) in the United States from 1970 to 2019.

Figure 3.  Average soybean yields (bushels per acre) in the United States from 1970 to 2016.

Figure 4.  Average soybean production (bushels) in the United States from 1970 to 2016.

Table 1.  Nutrient removal coefficient (pounds per bushel) provided by land grant universities for the primary corn producing states in the United States.

State (University) Potassium removal (K2O) Phosphorus removal (P2O5)
  pounds per bushel
Iowa (Iowa State Univ.) 0.22 0.32
Illinois (Univ. of Illinois) 0.28 0.43
Nebraska (Univ. of Nebraska) 0.28 0.40
Minnesota (Univ. of Minnesota) 0.19 0.28
Indiana (Purdue Univ.) 0.27 0.37
Kansas (Kansas State Univ.) 0.26 0.33
Ohio (Ohio State Univ.) 0.20 0.35
Missouri (Univ. of Missouri) 0.30 0.45
Wisconsin (Univ. of Wisconsin) 0.29 0.38

Table 2.  Nutrient removal coefficient (pounds per bushel) provided by land grant universities for the primary soybean producing states in the United States.

State (University) Potassium removal (K2O) Phosphorus removal (P2O5)
  pounds per bushel
Illinois (Univ. of Illinois) 1.3 0.85
Iowa (Iowa State Univ.) 1.2 0.72
Indiana (Purdue Univ.) 1.4 0.80
Nebraska (Univ. of Nebraska) 1.3 0.88
Missouri (Univ. of Missouri) 1.4 0.84
Ohio (Ohio State Univ.) 1.2 0.80
Wisconsin (Univ. of Wisconsin) 1.4 0.79

 

References

A General Guide for Crop Nutrient and Limestone Recommendations in Iowa.  2013.  Iowa State University Extension Publication – PM 1688.  Confirmed online August 4, 2020 at https://store.extension.iastate.edu/Product/pm1688-pdf.

Managing Soil pH and Crop Nutrients.  Chapter 8 of the Illinois Agronomy Handbook.  University of Illinois Extension.  Confirmed online August 4, 2020 at http://extension.cropsciences.illinois.edu/handbook/pdfs/chapter08.pdf.

Nutrient Application Guidelines for Field, Vegetable, and Fruit Crops in Wisconsin.  2012.  University of Wisconsin Extension Publication A2809.  Confirmed online August 4, 2020 at https://learningstore.uwex.edu/Nutrient-Application-Guidelines-for-Field-Vegetable-and-Fruit-Crops-in-Wisconsin-P185.aspx.

Shapiro, C., B. Krienke, and R. Ferguson.  2017.  You Can Postpone Phosphorus, Potassium, and Zinc Fertilizer Applications When… University of Nebraska Extension Publication.  Confirmed online August 4, 2020 at https://cropwatch.unl.edu/2017/when-can-you-postpone-soil-nutrients.

Fertilizer Recommendations for Soybean.  2006.  University of Nebraska Extension Publication G859.  Confirmed online August 4, 2020 at https://extension.unl.edu/statewide/nerec/Fert%20for%20Soybean%20g859%202006.pdf

Nathan, M., Y. Sun, and D. Dunn.  2007.  Nutrient removal values for major agronomic crops in Missouri report for 2006-2007.  Confirmed online August 4, 2020 at http://aes.missouri.edu/pfcs/research/prop706b.pdf.

Soil Test Interpretations and Fertilizer Recommendations.  2003.  Kansas State University Extension Publication MF-2586.  Confirmed online August 4, 2020 at https://www.bookstore.ksre.ksu.edu/pubs/MF2586.pdf.

Use 2020 Tri-State Fertilizer Recommendations.  Ohio State University Paulding County Agriculture News.  Confirmed online August 4, 2020 at https://u.osu.edu/pauldingag/2020/06/24/use-2020-tri-state-fertilizer-recommendations/.

Fertilizing Corn in Minnesota.  2020.  University of Minnesota Extension AG-FO-3790-D.  Confirmed online August 4, 2020 https://drive.google.com/file/d/1ZYbo7Hy3vIH8u5oLDnYD1x3E6oNlyV21/view.