A strong indication of whether a wheat crop is healthy comes at the elevator, when buyers measure crops for yield and test weight. Test weight is the measure of the grain's density, which gives customers an indication of both quality and potential flour yield. The standard test weight for wheat is 60 lbs./bu. Low test weight can lead to dockage.
In this installment of our “Grain Quality” series, we look at steps you can take to achieve a consistent test weight.
Many factors can affect test weight, including kernel size and shape, composition and moisture content. Large kernels and a high moisture content can reduce the crop's density, lowering the test weight. Another factor is disease, such as soil borne mosaic, powdery mildew, rust and scab. Growing conditions, of course, will affect kernel development and fill.
Understand Risks and Start Healthy with Good Seed
Monitor your fields closely for signs of pathogens that damage wheat quality. Any sign of disease should draw serious concern. In addition, it’s best to monitor weather patterns, disease outbreaks and upcoming forecasts. Southern winds can carry fungi spores hundreds of miles and patterns with increased moisture raise disease risks significantly.
Other factors to note are cropping history or tillage techniques. Crop residue from wheat, corn, barley and rye can all host damaging diseases that affect cereal crops. If you plan to follow one of these crops with wheat, incorporating the residue into the soil well before planting may decrease disease pressures that can negatively impact test weight.
Another way to limit risks is to select seed varieties with higher resistance to pathogens. Resistance ratings are available from seed dealers and your state's Extension service.
Maintain Crop Health Throughout the Season
“The best conditions for wheat and barley growth and yield potential are also ripe for disease development — that is, warm, humid weather,” explains Jody Wynia, cereals marketing manager for the Crop Science division of Bayer. “Scab, or Fusarium head blight, may infect grain heads when wet conditions occur during the flowering and grain-filling stages of plant development. Wheat infected with scab will still produce grain, but the grain may be small, lightweight and discolored, lowering its test weight.”
Fungicide products like Prosaro® are an effective choice for growers, especially during seasons with heavy disease pressure. For the best performance, apply Prosaro during flowering (Feekes growth stage 10.51) and before scab symptoms are visible. The broad-spectrum activity of Prosaro will protect the flag leaf, while holding back head diseases. In situations when the pressure of diseases such as powdery mildew and stripe rust becomes apparent early in the season before the crop reaches flag leaf stage, make an early season application of Stratego® YLD fungicide, followed by an application of Prosaro at early flowering.
“The best conditions for wheat and barley growth and yield potential are also ripe for disease development - that is, warm, humid weather”
- Jody Wynia
Finish Strong at Harvest
Managing harvest techniques can be as important as managing inputs. Jim Beuerlein, Professor, Horticulture and Crop Science at The Ohio State University, points out two common causes of low test weight:
- When frost, hail and insect damage prevent grain from filling completely and/or maturing and drying naturally in the field, starch molecules prevent shedding from absorbed water molecules that allow the grain to shrink to a normal size. Artificial heat drying removes excess water but the starch molecules do not shrink and the grain size does not change appreciably, so test weight (density) remains low.
- Grain matures and dries naturally in the field but is sometimes rewetted by rainfall, dew or fog causing the grain to initiate the germination process (precocious germination) before harvesting. During germination, oil, starch and protein digest to produce a new seedling. Although the process leaves small voids inside the grain and may dry in the field, the seed size does not change and the small voids result in a decreased test weight. Maximum test weight occurs when grain is harvested on the first dry-down and at a higher moisture.
Jochum Wiersma, Associate Professor and Extension agronomist outreach for the University of Minnesota, recommends that growers pay attention to controllable factors during harvest to ensure quality grain shipments. One method, he explains, is to turn up the combine blower speed to expel the lightweight seeds that reduce test weight.
“Managing wheat depends on a variety of factors. Right now, we don’t have a cookbook to tell growers what to do each year and every year,” said Wiersma. “Growers need to focus on producing the best wheat possible based on the lowest price per bushel, not lowest price per acre. If an input improves bushels or protects quality, growers should consider it.”
The best strategy for keeping test weights high is an aggressive year-round strategy: clean fields, vigorous seed, an effective disease-control program and skillful harvesting techniques.
Share your grain quality story about wheat with us and your fellow growers? Tweet us — @Bayer4CropsUS using #CerealExperts.
For more information about grain quality in wheat, call 1-866-99-BAYER (1-866-992-21937) or talk with your local sales representative.