Considerations When Planting Winter Wheat After a Spring Crop

• Best management practices for wheat seeded after a spring crop may vary substantially due to differences in the amount and type of crop residue left in the field after harvesting.
• Optimum seeding rates may differ due to expected available moisture during the growing season, seedbed condition, anticipated stand loss, planting date, and geography.

Winter wheat can be seeded during late summer or early fall after harvesting soybean, corn, grain sorghum, or other crops. The best management practices for wheat planted after corn or grain sorghum may be different than the best practices for wheat planted after soybean, due to the higher volume of residue produced by corn and sorghum crops. For example, less crop residue may require less tillage for seedbed preparation, resulting in a more favorable soil environment for no-till seeding and shorter-term nitrogen (N) immobilization from decaying plant residue.

Spring Planted Crop

Corn – Fusarium graminearum (also known as Gibberella zeae) is a fungus that can cause Gibberella ear and stalk rots in corn and can overwinter on corn residue. The overwintering fungus can produce spores in the spring which can potentially infect wheat, causing Fusarium head blight (FHB), also known as head scab. High humidity can encourage spore production and frequent spring rains can disperse the spores to the growing wheat crop. If the pathogen infects wheat, it can lead to yield loss and reduced grain quality due the to the production of a mycotoxin called deoxynivalenol, or DON, which is toxic to humans and livestock.^1,2

Sorghum – Sorghum can produce compounds that may be toxic to wheat, potentially reducing yield potential. The process of one species of plant producing chemicals to harm another species is known as allelopathy. Tillage can help to decrease the likelihood of allelopathy occurring. However, before performing a tillage operation, growers should consider any impact on erosion that tillage might have. Increasing the seeding rate can also help to offset any stand losses due to allelopathic effects.³

One method of reducing the chances of allelopathic effects occurring is to desiccate the sorghum crop prior to harvest. If the sorghum crop has reached physiological maturity and the grain moisture is less than 20%, an application of glyphosate can be used to desiccate the sorghum plants without affecting yield. A glyphosate application can also help insure that the sorghum will not continue to grow even after harvest (assuming a killing frost has not yet occurred), which can use soil moisture that is otherwise needed to get the wheat crop established. However, this option should not be used if the stalk quality of the sorghum crop is questionable, as increased lodging could occur.³

Product Selection

One important step to producing maximum economic yields is evaluating and selecting wheat products with high yield potential, high test weight, high grain quality, winter hardiness, drought tolerance, and resistance or tolerance to insects and diseases specific to your area. Since each seed product will have specific strengths and weaknesses, more than one product should be considered. Choosing multiple products of varying maturities can also help in managing risks associated with agronomic challenges such as late spring freezes or diseases such as Fusarium head blight and can aid in maintaining yield potential.

University and seed company performance trials can help identify top performing products, helping growers to best position products on their farms. Evaluating performance data from two or more years will provide a more accurate indication of yield potential over a broader range of growing environments. Purchasing certified seed can help ensure the wheat product is free of weed seed and certain diseases and offers the desired germination percentage. Product performance and ratings are available in publications from most wheat producing states including:

Kansas State University: MF991 Kansas Wheat Variety Guide 2024 (ksu.edu).

Oklahoma: https://okwheat.org/research-documents/variety-trials/

Planting Date

Wheat should be planted as soon as possible after harvesting the spring planted crop. This helps to give the wheat crop adequate growth potential before going into winter dormancy and allows for the formation of fall tillers, which are more productive than spring-initiated tillers.^1,4

Seeding Rate

Like planting dates, recommended seeding rates will vary from state to state and even within a state. For example, in the low-rainfall area of western Kansas, seeding rates are generally lower than in central and eastern Kansas. In western Kansas, recommended seeding rates range from 600,000 to 900,000 seeds/acre (40 to 60 lb/acre with 15,000 seeds/lb products). Recommended seeding rates increase to 750,000 to 900,000 seeds/acre in central Kansas and to 900,000 to 1,125,000 seeds/acre in eastern Kansas. Under irrigation, the seeding rate recommendations may further increase to 1,350,000 seeds/acre.⁵

Additionally, the University of Wisconsin recommends seeding rates of 1,300,000 to 1,600,000 seeds/acre for timely planted wheat, while the University of Illinois suggests seeding rates of 1,500,000 to 1,700,000 seeds/acre.^6,7 Consider increasing seeding rates for later planting dates to help the stand compensate for a shorter fall season and associated reductions in fall tiller development.

Growers may want to consider increasing seeding rates in challenging high-residue environments where achieving desired stands may be difficult. Since delayed planting may reduce the incidence of fall tillering, increasing the seeding rate may help to overcome a lower tillering rate.

Consider contacting your local county extension office for recommended seeding date and seeding rate for timely planted or late planted wheat for your area.

Post-Harvest Considerations for Tillage and Residue Management

Residue management of the spring planted/fall harvested crop begins by confirming that the stalk choppers and spreaders on the combine are distributing residue evenly. If improvements in distribution are needed, always refer to the combine operator’s manual before performing any maintenance or adjustments.

If soil moisture is lacking after harvest, no-till wheat seeding may be an option to conserve soil moisture that contributes to quicker wheat emergence. No-till wheat planting may be more successful after a soybean harvest than a corn or grain sorghum harvest, due to there being less crop residue on the soil surface.

The amount of corn residue produced per acre will vary by yield, weather, soil type, and corn product. As corn yields have generally increased in recent years, the amount of residue has increased proportionally. Generally, the ratio of corn grain weight to residue weight is about 1:1 on a dry matter basis.⁸ Residue is desirable for soil erosion protection; however, excess corn residue can cause no-till planting to be problematic. Also, corn stalks and cobs are low in nitrogen (N) and high in carbon (C), resulting in a high carbon to nitrogen (C:N) ratio. Initially, N may be tied up as the residue breaks down, which may temporarily reduce its availability for the wheat crop.

One option to manage heavy residue left by a high yielding corn or grain sorghum crop is harvesting the residue. This could be used as a feed source as well as possibly reducing the potential for immobilization of N since there will be less residue to breakdown. Residue harvest should be managed so as to leave enough residue on the soil surface to protect against wind or soil erosion. Although this may delay the planting of wheat, it may also provide a better soil environment for the wheat crop to establish a desired stand.

The University of Kentucky conducted a three-year research project focusing on corn residue management for no-till wheat after corn harvest. The study was conducted at three locations, and treatments included removing residue, chopping with a rotary mower, and chopping with a flail mower prior to seeding. Additionally, if corn residue was not shredded, wheat was either no-till planted parallel to the harvested corn rows or diagonally to the corn rows.

Results of the study indicated small but significant yield differences between residue treatments when planting no-till wheat with favorable growing conditions (mild fall/winter and early/warm spring). However, with unfavorable weather condition (cool fall and/or spring or severe winter), the following observations were noted:

• When corn residue was not shredded, planting diagonally to the corn rows resulted in higher yield potential during all three years.
• The use of a flail mower resulted in more uniform distribution of residue compared to using a rotary mower.⁹

Seeding Equipment and Seeding Depth

Heavy corn residue may create a concern about achieving uniform planting depth, especially with shallow seed placement when wheat is planted no-till. Good seed-to-soil contact is necessary for quick germination and emergence. Shallow planting may inhibit the seedling’s access to sufficient soil moisture, increase the risk of unhealthy crown development, and predispose the seedling to freeze injury during harsh winter conditions.¹

Producers should make sure that their no-till drill is able to cut through surface residue in order to achieve adequate seeding depth in the thickest layers of crop residue and that residue is not too wet to cut through. “Hairpinning” may occur when residue is not sufficiently cut and is instead pressed into the seed slot by the seed furrow opening discs, preventing adequate seed-to-soil contact. Additional ballast (weight) may need to be added to the drill to maintain adequate downforce to cut through the residue and place seed at the target depth. Shredded residue, with smaller pieces uniformly distributed prior to planting, may result in a more uniform planting depth.^1,9

Nutrient Management

A current soil test should be used to determine existing soil nutrient levels, especially pH, phosphorus (P), and potassium (K) to avoid future over- or under-fertilizer applications. Phosphorus and K removals per harvested bushel of wheat, soybean, corn, and grain sorghum are listed in Table 1, as is P and K removal per harvested ton of corn silage (67% moisture) and wheat straw. If needed, consider applying P and K fertilizer for both the spring crop and winter wheat prior to spring planting.

Generally, nitrogen (N) is the nutrient needed in the greatest quantity for winter wheat and its application usually provides the largest contribution to maximizing yield potential. Nitrogen application rates are influenced by expected yield, soil type, previous crop residue, and other factors. An additional 30 lb/acre of N should be added to the recommended rate following grain sorghum or corn so that the additional N will help to break down the residue and overcome the issue of N being tied up. Do not give a credit to the N application rate when following soybean, since the organic N release from the soybean crop will most likely occur too late to be of benefit to the winter wheat crop.³

Herbicide Product Selection

Consider re-cropping restrictions for seeding wheat when choosing herbicide products to be applied for spring planted crops such as corn, soybean, sorghum, and others. Some of the soil-applied residual herbicides may have a three- to four-month re-cropping restriction in order to seed wheat. The amount of precipitation received (or irrigation water applied) after application can influence the potential for injury due to herbicide residues remaining in the soil. Always read and follow pesticide label directions.¹

Sources:

¹Haag, L., Roozeboom, K., and Ciampitti, I. 2021. Management considerations for no-till wheat following sorghum or other summer crops. Kansas State University Extension, Agronomy eUpdates. https://eupdate.agronomy.ksu.edu/article/management-considerations-for-no-till-wheat-following-sorghum-or-other-summer-crops-463-4

²2012. Know potential risk of wheat after corn. FarmProgress, OhioFarmer. https://www.farmprogress.com/wheat/know-potential-risk-of-wheat-after-corn

³Bean, B. 2019. Double cropping wheat behind grain sorghum. Sorghum Checkoff. https://www.sorghumcheckoff.com/agronomy-insights/double-cropping-wheat-behind-grain-sorghum/.

⁴Latzke, J.M. 2023. Consider these steps when no-tilling wheat into summer residue. Kansas Farmer. https://www.farmprogress.com/crops/consider-these-steps-when-no-tilling-wheat-into-summer-residue

⁵Paulsen, G.M., Sears, R.G., Shroyer, J. et al. 1997. Wheat production handbook. Kansas State University. https://bookstore.ksre.ksu.edu/pubs/wheat-production-handbook_C529.pdf

⁶Nafziger, E. 2009. Chapter 4: Small grains and grain sorghum. In, Illinois agronomy handbook 24^th edition. University of Illinois. https://extension.illinois.edu/sites/default/files/2023-10/small_grains_and_sorghum.pdf

⁷Conley, S. and Gaska, J. 2012. Top 8 recommendations for winter wheat establishment in 2012. University of Wisconsin, Integrated Pest and Crop Management. http://ipcm.wisc.edu/blog/2012/09/top-8-recommendations-for-winter-wheat-establishment-in-2012/

⁸Sheaffer, C., Lamb, J., and Rosen, C. 2024. Harvesting corn stover. University of Minnesota Extension. https://blog-crop-news.extension.umn.edu/2024/03/harvesting-corn-stover.html

⁹Herbek, J., Murdock, L., James, J., and Call, D. Corn residue management for no-till wheat. University of Kentucky. https://wheatscience.ca.uky.edu/sites/wheatscience.ca.uky.edu/files/99-00pg20.pdf

Web sources verified 10/21/24. 1710_457976