It’s possible to have a perfect stand in some areas of a field while others are lodged and tangled at harvest.
Lodging is a costly problem, especially for wheat producers who are pushing for higher yields. The good news is that lodging can be significantly reduced or almost eliminated using careful crop management techniques.
Lodging is a term used to describe regions of cereal fields (or sometimes whole fields) that fall flat on the ground. Some plants try to stand back up, but at that point yield has already been impacted. Lodging can also slow harvest, increase grain losses and make no-tilling difficult as a result of the volume of residue.
Lodging triggers. There are a number of reasons for lodging, but the most frequent is an excessively dense canopy between the stem elongation and heading stages. Dense canopies are often caused by excessive early nitrogen rates or soils with high volumes of residual nitrogen, such as animal manure. If heavy rains are coupled with high winds later in the season, the dense canopies cannot support themselves and the plants fall flat on the ground.
In most examples there is a significant yield reduction, sometimes as much as 50%, especially when areas of the fields lodge during the early grain-filling stages. In some examples there are grain quality issues associated with lodging, such as test weight reductions. The direct yield loss of lodging is frequently caused by stem kinking when the plants fall over, but reduced photosynthesis and increased disease pressure indirectly add to the yield loss.
To help avoid lodging, producers need to count tillers early in the spring to determine if fields are too thick. Count plants and tillers to determine the total number of tillers per square foot or per square yard.
If wheat fields have more than 750 tillers per square yard at the mid-tillering stage, a split application of nitrogen will help reduce head counts at harvest. If tiller numbers exceed 1,000 per square yard, consider holding off on the spring nitrogen until around jointing.
Splitting nitrogen allows 30% to 40% of the nitrogen to be applied early to maintain plant health with the balance applied at or shortly after jointing, when tillering is completed. In many cases, growers who split-apply nitrogen can increase their total nitrogen rates, which boosts yield and enhances standability compared with an early single application.
Other factors that cause wheat lodging include:
- Poor standability varieties. When helping farmers select varieties, I encourage them to select shorter, stiffer straw wheat varieties because they stand better. This allows farmers to push nitrogen rates higher and feed additional yield potential without the risk of lodging.
- Poor field uniformity. Some producers are still struggling with nitrogen application uniformity, which results in streaked fields and alternating lodged strips of wheat. Many farmers have not improved their spreading equipment since the price of nitrogen has tripled in recent years.
Try to avoid using spinning-disk spreaders; even if they are properly calibrated, they tend to have a hard time spreading light materials with fines, especially in windy conditions or on rolling fields. Dry fertilizer is best spread with air trucks. If there are no air trucks available in your area, consider using liquid nitrogen through a row-crop sprayer. The addition of stream bars will provide uniform delivery and basically eliminate leaf scorch by dribbling the nitrogen into the canopy rather than covering leaves with a flat fan application.
- Stem-based diseases. Some producers across the Central Plains raise wheat year after year. In this environment, diseases such as strawbreaker can damage the wheat stems and compromise standability, especially when coupled with wind and rain. Rotating away from wheat is the most effective way to reduce the likelihood of stem-based diseases, but some foliar fungicides offer adequate control as well.
- Poor plant anchorage. Producers who plant wheat into loose, conventional soils can see lodging later in the season, especially following heavy rains and high wind. In most of these examples, the soil did not have adequate structure to anchor the plant, causing the soil around the roots to move, which allows the plant to fall over. Improving the consolidation of the seedbed using reduced tillage or no-till practices will help keep the plants upright.
What’s to come. As optical crop-sensing equipment continues to evolve, so does the ability to spatially distribute nitrogen throughout a field.
Environmentally, this is important, but it also offers the opportunity to reduce lodging. This is achieved by sensing fields and perhaps adding historic yield data. Regions of a field that are more yellow receive more nitrogen in a real-time post application. Deeper soils within a field are likely to be greener, so less nitrogen is applied to these areas. Swath control is available on most sprayers now, which helps reduce nitrogen overlap and lodging at the ends of the field.
Farmers in Europe have access to new growth regulator chemistry. These products help control plant height and improve stem thickness to allow 140 bu. to 180 bu. per acre yields that stand up at harvest. Currently, there aren’t any good growth regulators available for cereals in the U.S., but I expect new products to be available in the next five years.
- February 2012