Wheat Stand Assessment

Producers often focus on spring wheat assessments for nitrogen and weed management, but forget the importance of assessing wheat for germination and tillering before winter. While both are important, skipping fall assessments can lead to a yield reduction that spring management cannot overcome. This article outlines methods for assessing wheat stands and addressing weed and nitrogen concerns in the fall and spring.

Fall Tiller Counts and Interpretation

While current research suggests that most wheat varieties benefit much more from spring nitrogen than fall nitrogen, scouting and tiller counts help us determine which fields might benefit from fall nitrogen.

First, determine tillers per square foot using the University of Kentucky's method. This should be performed at Feekes 3 (roughly Zadoks 22-26), counting shoots and tillers. For a detailed guide to wheat growth staging, visit "Wheat Growth Stages and Associated Management." This method involves counting plants or tillers in 1-, 2-, or 3-foot sections along a row. The stand count can then be determined using Table 1. For example, if you count 80 plants in 2 feet, on 7.5-inch spacing, that equals 64 plants/sq foot. Note that the table provides an estimate of the relationship of the wheat stand to yield potential and is only a guide. Factors like plant vigor, weather, disease, fertility management, planting date, and variety influence how a wheat stand ultimately responds to achieve its final yield potential.

Fall counts of 80-100 tillers/sq ft indicate a strong stand and good potential for winter survival and yield. While these stands will still need spring nitrogen, they likely won't benefit from a fall application or an increased rate. Fields with tillers between 80 and 50 may respond to nitrogen fall applications, but responses will be more variable and less predictable, depending on weather and soil type. If less than 50 tillers per sq foot, a nitrogen application of 15-30 lbs/acre will encourage fall tillering. Adding fall nitrogen will hasten growth, potentially leading to winter kill if applied to heavy or well-growing stands, especially in fields with high organic matter and soil nitrogen.

Additionally, while assessing stands, be sure to scout for weed growth. When scouting in a burst of warm weather during the late winter, it is not uncommon to find speedwell (in bloom), chickweed, and dead nettle moving forward in stands that did not receive an herbicide in the fall, while those that did are extremely clean.

Spring Tiller Countsand Interpretation

During spring, we often experience a couple of weeks of rapid growth, and growers begin asking themselves whether to move up applications, which may or may not be helpful for yield and profit. A spring stand assessment is essential for determining winter survival, yield potential, and whether this application should be moved up. Spring checks need to be completed between Feeks 3-5/6. Counting early, Feeks 3, will provide you with survivability and initial tillering rates and should be completed on fields that had low tillering in the fall. Stronger tillered fields can be checked later, Feeks 5/6, prior to an application being made.

Using the method and table from above in Fall Tiller Counts and Interpretation, calculate tillers/ sq ft. Once the tillers per sq. ft. for the final stand have been calculated, they can be compared with the information in Table 2 to determine potential yield. If the field is averaging 19 plants per square foot, the yield potential is 90-95%. If the average is 10 plants per square foot, the yield potential will be closer to 55%.

^a This provides an estimate of the relationship of the wheat stand to yield potential and is only a guide. Many factors (plant vigor, weather, disease, fertility management, planting date, and variety) influence how a wheat stand ultimately responds to achieve its final yield potential.

Fields with stand counts below 15 plants per square foot have yield potential below 75 percent (Table 2) and should not be kept; instead, they should be rotated into corn or soybeans. While this may seem like a financial waste, consider the inputs needed to produce the crop, the sale value, and the opportunity cost of not producing a full-season crop. For fields with a yield potential of 75 to 90%, a first top-dressing application close to green-up, Feeks 3-4 to promote tillering and help maintain yield potential, and a second top-dressing application around Feeks 6-8 to apply the remainder. For fields with a potential of 90% or greater, nitrogen should be applied between Feeks 3 and 6, with potential for a second application around Feeks 8, depending on the timing of the first application, nitrogen source, and desired quality.

To determine nitrogen application rate, a formula that accounts for total nitrogen and the yield goal is used. While these formulas may change by wheat type and location, the Pennsylvania Agronomy Guide recommends 1.0 lbs of nitrogen per bushel of expected wheat. A 100-bu/acre field needs 100 total nitrogen units. Total nitrogen includes fertilizer applied at planting, fall, and spring.

Example: The fall tiller assessment indicated 45 tillers/sq ft, so 15 units/acre was applied. At a Feeks 3 assessment, tiller count was 17/sq ft, indicating a 78% yield potential. To further increase tillering, 40 units were applied at Feeks 4. If the yield goal is 90 bu/acre, and 55 (15 in fall and 40 at Feeks 3) units have already been applied, the Feeks 6 application should be 45 units/acre.

Spring evaluations are not just for tillering and nitrogen assessment. Consider drowned out in low-lying spots, heaving or the pushing of the plant out of the soil, and exposed roots. These problems are more prevalent in low areas and areas of high clay content. If areas affected by heaving or thinning stands make up most of the field area, it might be worthwhile to consider rotating out of wheat and into a corn crop to utilize any N that may have been applied. Depending on which herbicides were applied and their respective replant restrictions, soybeans may also be planted.

Interested in Learning More about Winter Wheat Management?

If you are interested in learning more about winter wheat management, tune in to Season 2, Episode 8 of the Agronomy Highlights Podcast. In this episode, Penn State Extension agronomy experts tackle winter wheat management from two perspectives: general agronomy and soil fertility. From planting dates and seeding rates to nitrogen applications in fall and spring, this episode covers all the basics of successfully growing a crop of winter wheat. Listen on our website, Spotify, Apple Podcasts, or wherever you listen to podcast content.

Additional Resources

The tables in this article and other information were obtained from the Comprehensive Guide for Wheat Management in Kentucky, developed by the University of Kentucky Extension. The Ohio State University article When and How Much Nitrogen to Apply to Wheat, can provide a detailed look at assessing wheat stands. Lastly, if you would like to take a deeper look at fall applications, read Are fall applications of N to winter wheat beneficial? by the University of Wisconsin-Madison.