FORESIGHT FOR SUCCESSFUL CROPPING SYSTEMS Changing the Wheat Yield Trend

By Zachary Fore
U of M Cropping Systems Specialist
forex002@umn.edu

Whenever I write this column my goal is the same:  to provide information that can help farmers grow crops more profitably and in an environmentally sustainable manner.  There is a simple formula for profitability in agriculture: Yield x Price – Expenses = Profit. This means that to increase profitability we have to increase yield, get a higher price, and/or decrease expenses. 

Farmers need to continually work on all three of these, but which one do you think is the most important?  Where should you spend most of your effort? The answer to these questions varies from farm to farm and from region to region.  However, for northwest Minnesota, crop production and economics data reveals a clear story: yield is by far the most important factor in profitability. That’s why my columns so often focus on increasing yields. In this column we are going to look specifically at hard red spring wheat yields.

Hard red spring wheat (HRSW) is a major crop in Minnesota, with nearly 2 million acres planted in 2001. In northwest Minnesota where most of the wheat is grown, from 1970 through 2001 the highest average yield observed was 56.3 bu/a in 1985.  The lowest yield during that period was 24.7 bu/a in 1994, and the average yield over the period is 37.9 bu/a.  Improved genetics and production practices are expected to result in yield increases over time. However, as can be seen in the chart below, wheat yields in NW Minnesota have been highly variable, with a trend line that is nearly flat.  The 2002 yields are likely to be significantly below the long term average, which will further lower the trend line.

As an agronomist working in NW Minnesota, this graph is the equivalent of my report card with a big fat D on it.  If the trend line starts going down it will be an F.  This trend line suggests that we are not doing a very good job of identifying and eliminating yield limiting factors.

At the same time the yield line is flat the price line is going down, especially when inflation is accounted for.  In 1998 constant dollars, the price of wheat was about $5/bu in 1970, increasing to over $15/bu in 1975, and decreasing to commonly less than $4/bu in recent years. During the same period the yields of corn and soybeans have been increasing at a healthy rate. NDSU researchers recently published the  table bottom left on gross returns in ND for corn, soybeans, and wheat.

Gross Returns ($/acre)   Corn Soybeans Wheat Average 1961-1965 34 38 38 Average 1997-2001 190 152 152 Change (%) 449 304 304 Source: Wilson, Janzen, Dahl, and Wachenheim. Agribusiness and Applied Economics Report No. 509. Jan. 2003

Attainable average wheat yields for the area are at least 56.3 bu/A (1985).  Maximum yields, though unknown, are significantly higher than attainable yields. Each year various factors reduce yields, resulting in observed yields (graph above). Understanding what those factors are and how much each factor contributes to reducing yields is critical to profitable wheat production.

So, what are the major factors reducing wheat yields in the region?  Lots of people have lots of different ideas.  To get a handle on what people think the yield reducing factors are, I sent out a brief unscientific survey.  I asked numerous farmers and agronomists to give me a list of five things they felt have been the most important factors limiting wheat yields since 1971, ranked from most to least important. The table at below summarizes the 14 responses I received.

Importance Ranking Yield Reducing Factor #1 #2 #3 #4 #5 (# of responses by ranking and factor) Weather 5     1   Too Wet 6   1 1 1 Too Dry       2   Too Hot   1     1 Diseases   1 1     Scab 2 2 1 1 1 Leaf Diseases   2 3 2 1 Root Rot     2     Late Planting 1 3   1 1 Genetics   2 2   1 Weeds         3 Rotations   1       Soil Compaction       1   Low N rates       1   Lodging       1 1

The big winner (loser, I should say) is clearly the weather, with the majority indicating specifically that it was too wet. Diseases were #2, with scab and leaf diseases leading the way.  Number 3 was late planting, and number 4 was genetics.  Weeds, rotations, soil compaction, low N rates, and lodging received passing mention. Not only was weather ranked #1, it is also an important factor contributing to #2 - diseases, and #3 - late planting.

I have often heard it said that the weather is the biggest problem, and we can’t do anything about the weather.  I believe it is true that we can’t change the weather, but we can manage around it and respond or react to it better. After all, we really have been managing around the weather since we first started farming here.  We select crops that are adapted to our conditions, we plant them when they have the best opportunity to produce, we make ditches to drain away excess water, and so on.

As I have previously stated often in this column, I believe that surface and subsurface (tile) drainage are absolutely essential components of profitable production systems.  We need to consider water not just as a product of the weather, but to a great extent as a manageable variable in our production system.  Planting date is primarily a weather/water management issue. If we can manage our water it will greatly assist in planting at or near the optimal date.

What about diseases? They have certainly impacted wheat yields. The yield graph shows a lot of variability in the 1990’s, which is largely a result of scab. We now know how different varieties respond to scab even if we do not have outright resistance.  We also know that we can control scab to some extent with fungicides.  Leaf diseases seem to be a problem every year.  We have varieties with significant tolerance to leaf diseases, and we have fungicides that do an excellent job controlling them.  In addition, we have decision guides that greatly aid in determining when a fungicide should be applied.

And, what about genetics?  Are we making progress in developing higher yielding wheat varieties? The data indicate that our plant breeders are making progress. The Minnesota Varietal Trials Bulletin shows that from 2000-2002, Marshall, a 1982 release and a high yielding variety for its time, yielded about 17% less than the highest yielding current varieties.  Although not earth shattering, this represents an average yield increase of about 0.85% per year. It is likely that the emphasis on identifying scab resistance has distracted breeders from focusing on yield.

Assess your most yield limiting factors. Make a list and prioritize it. For each item on the list ask yourself why it is a problem – make sure you identify the root cause, not just the symptoms. Be very critical and think creatively – don’t be too easily satisfied with answers like “I can’t do anything about that.”  If we do a good job of identifying yield limiting factors, we can concentrate on managing them, and get our wheat yield trend moving upward the way it should be.