Why Was Wheat Protein So Low in 2004?

While genetic differences exist in wheat varieties that trigger different protein levels, the biggest influence will be caused by the environment where the wheat is grown.

By David Boehm

As I visit with growers from across the region about the 2004 growing season, one of the first questions I get is “why were wheat proteins so low?” It has been an issue accentuated by strong wheat protein premiums and discounts.

Some growers are quick to look at variety choice as the first reason for lower proteins.  While genetic differences exist in wheat varieties that trigger different protein levels, the biggest influence will be caused by the environment where the wheat is grown. 

Critical environmental factors include excess rainfall, growing temperature, and soil fertility.  These three factors will affect protein levels regardless of the genetic potential of the wheat variety. As an average across locations, varieties such as Trooper, Russ, and Knudson are known to have protein levels just over 14% while Granite, Alsen, and Dapps can be over 15%. However, few cases of 14% protein were reported in the east, regardless of variety, because of the high yields that offset protein levels.

Excess rainfall –North Dakota State University soil scientist Jay Goos reports that excessive rainfall during the growing season has a big impact on available N. Goos says nitrogen can be leached through the soil profile by excessive rainfall, and adds that the loss in soil N between fall and spring can also be larger than expected in wet fall and winter seasons, particularly in sandier soils. 

With excess water and good growing conditions, wheat plants will send their roots laterally across the soil profile looking for moisture, and not downward.  If rains persist, N will be leached to a level below the shallow root development.  Further, if subsoils are too wet, deeper rooting ability may be impaired, thus decreasing N uptake efficiency. 

Growing temperature –Wheat is a cool season plant that grows very rapidly under moderate temperatures, producing more overall plant material.  This excessive plant growth also effects plant height and subsequent straw strength.  Under heat and drought stress, the natural reaction for a wheat plant will be to store less carbohydrates (yield) and conversely store more protein.   This will happen particularly if plants are stressed after heading and during grain fill.

July and August in 2004 were much cooler and wetter than 2003, and plants were not under any heat stress, thus causing the wheat plants to generate more carbohydrates but less protein.  In southwestern N.D., where the climate was drier and generally warmer, protein levels were not problematically low.

Gerald Smith, a crop consultant in the Red River Valley, points out three sources of N available to the wheat plant: residual N, added fertilization, and mineralization of organic matter.  The organic matter in the soil breaks down to N under higher soil temperatures.  He feels the cool temperatures that existed in the Red River Valley region last year did not allow for adequate mineralization.

Soil fertility – This is the most important aspect of wheat production and the only factor  producers can control.  It was very common to hear of low protein grain where yields were very high, even higher than the yield goals set in the producer’s fertility program. Indeed, it’s hard to expect a field fertilized for 60 bushels per acre to have good protein when it produces 70-80 bu/ac.

A low-to-moderate protein level variety that is under-fertilized for its yield will very easily fall below 14% protein. Setting achievable yield goals, especially for higher yielding varieties with lower than average protein, is critical for striking a balance between yield potential and the 14% protein objective.

Goos says the standard recommendation for 2.5 lbs N for each bushel of yield is a guide to produce grain of good quality in normal years.  When growing conditions change a producers expected yield, he says N recommendations need to change as well, to maintain protein levels. 

What can we expect for the upcoming growing season? 
Again, weather is a key factor.  If next spring repeats the same cool and wet weather, we might see the same results.  Consider your fall tillage and fertilizer programs, which could also have an influence on your soil N situation. If you have fields not worked last fall, you may have less organic matter breakdown. For some growers, especially west central Minn., rainfall levels in the fall season were much higher than normal, potentially leaching even more N. 

Soil testing is the only accurate way to determine the amount of N available.  Smith says fall nitrogen soil levels in the east are around 10-15 lbs less than a year ago.  Jason Hanson, and agronomist with Agriliance, reports the same 10-15 lb. decrease in the Devils Lake area. He warns that because of the late harvest – as well as a “wait and see” approach toward fertilizer prices – more growers may have delayed fertilization this past fall. If so, the demand for fertilizer from local outlets this spring could be high. He suggests that producers develop a plan well ahead of time for their fertilizer needs.    

Goos also suggests that growers watch the sulfur level in the soil, as sulfur is a component of grain protein production. Hanson also mentions sulfur as important to the wheat plant, as well as phosphates that help with root development, tillering and plant vigor, which all contribute to yield.

With a repeat of 2004 early growing conditions, growers should consider topdressing with addition N as urea or 28% liquid N at the appropriate growth stage.  Additional N applications in wet areas with good early season growth can help maintain protein levels and increase grain yield. This will be especially true in light and sandier soils.

Mitch Strom, a consultant with Opti-Crop, reports that a producer in the Red River Valley produced about 65 bu Knudson at about 14.7% protein with the use of additional N.  This illustrates that while it may be impossible to predict how a growing season will develop, you can still play a role in how your wheat crop develops, if you plan ahead and manage appropriately and responsively according to growing conditions.

Factors/Reasons  for Low Grain Protein in 2004

• Soil nitrogen available to plant
• Cool growing season
• Great early plant growth
• Little soil organic matter mineralization
• Excess water and leaching
• Lack of heat and water stress in July
• Root growth was lateral and not downward
• Expected yield goals were not high enough
• Variety choice

Fertility outlook for spring 2005

• Lower available soil N in many areas because of high 2004 fall moisture
• Reduced fall tillage causing less organic matter mineralization
• Reduced N applied in fall 2004 (Reasons include late harvest, high price)
• High N costs still likely this spring

What to do to manage wheat fertility in 2005

• Fall soil test results/spring soil test will be critical
• Increase N for lower protein varieties
• Set achievable yield goals for fertilization, taking previous N credits of previous crop into account
• Consider split application of N if there’s good early plant growth and excessive rainfall, especially on lighter soils
• Don’t forget other soil nutrients – consult an agronomist about your fertility needs, with soil test results serving as a guide.

David Boehm is the regional manager for AgriPro Wheat. A member of the Minnesota wheat checkoff-funded Minnesota Small Grains Research and Communications Committee, Boehm received a master’s degree in plant breeding from NDSU and was involved with protein N research as a grad student.  He can be reached by email at david.boehm@agripro.com .