Production Resources

Wheat yield components: What are they and how do they impact management decisions?

Wheat

Do you know where your wheat yield comes from? Understanding wheat yield components and how management choices influence each component can help guide decisions to maximize yield. What are yield components? Yield components are the primary factors that contribute to overall grain yield. Environment, plant stress and resources influence yield components. There are three main yield components.

Yield components

Heads per ft² (heads/ft²) = plant density x heads per plant
Grains per head (grains/head)
Grain weight

The amount each yield component impacts yield varies. For instance, the number of heads per ft² has a larger influence on yield variation than grain weight, although both components are important. Management effects on yield components are not independent of each other. Instead, they can have interactive or conflicting relationships where the increase of one can mean a decrease in another. Below is more information on wheat yield components and the management practices that influence them.

Heads per ft²

The number of heads per square foot is influenced by both plant density (the number of plants per square foot) and number of heads per plant.

Plant density

Plant density is primarily determined by farmer seeding rates and seed germination percentage. Plant density strongly influences heads/ft² and overall yield. Therefore, seeding is the one opportunity to maximize this yield component.
- Management considerations:

Table 1. Management considerations that influence plant density.

Seed Quality	Use certified seed or a high-quality seed source. Understand seed qualities, such as germination, vigour, seed weight (TKW), mechanical damage, and disease levels. Use an accredited lab to conduct seed quality evaluations.
Seeding Rate	Recommended target plant density in Manitoba for wheat is 23-28 plants/ft² (Manitoba Agriculture, 2025). Seed using the target plant population method to maximize plant population.
Seeding Date	Wheat is usually planted from late April to the end of May in Manitoba. Early seeding has been shown to increase crop yield potential, as crops can better utilize water and nutrient resources, but there are still risks to seeding early which should be considered. Producers are increasingly moving away from using calendar dates to guide seeding timing and are instead using soil temperature. The minimum soil temperature for wheat seed germination is 4°C (Manitoba Agriculture, 2025). Research conducted in Saskatchewan and Alberta found the optimum soil temperatures to maximize yield and quality was 2-6°C at seed depth (Collier et al., 2020). For more information on seeding date check out these MCA articles on early and delayed seeding of spring cereals.
Seeding depth	Wheat should be planted 1.5-3 inches deep (Manitoba Agriculture, 2025). Optimum seeding depth can change depending on soil and environmental conditions. Check out this MCA article for more information on seeding depth decisions in dry soil conditions.
Seed treatment	Consider a fungicide or dual (fungicide/insecticide) seed treatment. Seed treatments can help with biotic and abiotic stress mitigation.

Heads per plant

Heads per plant is determined by the number of yield-contributing tillers developed per plant. This yield component has a strong influence on overall yield and is quite variable. Many factors affect this, such as resources available during tiller initiation, seeding rate and environmental conditions. Furthermore, for a tiller to contribute to yield it needs to fully develop and survive until maturity.
Tillers are initiated from the 3-leaf stage (GS 13) to stem elongation (GS 30), while tiller mortality occurs once resources are limited until anthesis begins (FAO, 2002). Tillers per plant are impacted by environment but also variety.
- Research conducted in Manitoba on spring wheat found that tillers range from 1.9 to 2.6 per plant, depending on the variety (Mangin, 2022).
- Research from North Dakota found heads per plant range from 2 – 2.64. Tillering capacity was significantly influenced by variety and environment (Mehring, 2016). Generally, as the seeding rate increases, the number of tillers decreases (Mehring, 2016).
- Furthermore, the main stem and tillers don’t contribute equally to grain yield. Every consecutive tiller initiated contributes less than the one before (Otteson et al., 2008).

Table 2. Per cent of yield contributed by main stem and tillers from hard red spring wheat grown in North Dakota (Otteson et al., 2008).

Stem	Percent contribution
Main stem	53-56
First tiller	31-33
Second tiller	10-12
Third tiller	2

Agronomic practices such as nutrient management and seeding rate impact heads per plant. Nutrient limitation during early growth and tiller initiation will reduce the number of heads per plant (Mangin, 2022).

Grains per head

Grain number per head is determined by the number of spikelets and florets (spikelet sub units) on a wheat head (Figure 2). Spikelet and floret development initiates around the 3-leaf stage (tiller development) until stem elongation (GS 30) (Mangin, 2022).

Figure 1. Wheat head parts during flowering. Photo credit: University of Wisconsin (used with permission).

Although development of these plant organs occur early in the growing season, the survival of florets at each spikelet will determine the final grain number.
Typically, only 20-30 per cent of the florets which are initiated survive through stem elongation to flowering (Slafer et al. 2014).
Resource limitations of nutrients and water, extreme heat during flowering and shading prior to flowering reduce the number of grains per head (FAO, 2002).
Adequate early season nitrogen is required to ensure resources are available when grains per head are being determined. Research from Mangin (2022) suggests nitrogen fertilizer application at flag leaf stage may be too late to correct nitrogen requirements and influence the number of grains per head.
Grains per head is also influenced by variety, thus genetics play a role. For instance, in research conducted by Mangin (2022), AAC Brandon had significantly more grains per head compared to AAC Cameron and Proposer.

Grain weight

Grain weight (TKW) is important but has the least plasticity of all wheat yield components.
Grain weight is strongly influenced by genetics and environmental conditions during grain fill, the period between flowering and crop maturity. High temperatures and low soil moisture will limit the overall grain weight.
- Management considerations:

Table 3. Management considerations that influence grain weight.

Seeding early

Utilizing seeding practices that can reduce the number of days during grain filling where hot and dry conditions are experienced has the potential to mitigate adverse effects on seed weight.

Foliar Fungicide

Protecting the yield-bearing leaves is important to fulfil plant yield potential (refer to paragraph below). Leaf diseases such as septoria complex, tan spot or rust can reduce the photosynthetic leaf area, thus reducing the energy going towards filling the grain. Protecting these leaves with a foliar fungicide is warranted if disease levels and environmental conditions are favourable for disease development.

Yield contributing plant parts

Understanding the plant parts that photosynthetically contribute to yield helps determine how to handle disease and fungicide application decisions. Leaf contribution to grain yield is not equal across leaves or plant parts. Furthermore, yield contributing leaves change by crop type, even between cereals like barley and wheat. The wheat flag leaf, head and penultimate leaf contribute most to wheat yield, so protecting these leaves is vital to protecting your yield. For more information about fungicide application decisions, check out this article by MCA about early season disease management.

Figure 2. Percent contribution to grain yield by plant part in wheat and barley. Image courtesy of Alberta Grains.

References

Acevedo, E., Silva, P., and Silva, H. (2002). Wheat growth and physiology. In B.C. Curtis, S. Rajaram, H. Gómez Machpherson(Eds.), (2002), Bread Wheat Improvement and Production (n.a.). FAO.

Collier, G.R.S., Spaner, D.M., Graf, R.J., and Beres, B.L. (2020). The integration of spring and winter wheat genetics with agronomy for ultra-early planting into cold soils. Front Plant Sci.11(89). https://doi.org/10.3389/fpls.2020.00089

Mangin, A. (2022). Agronomic practices to minimize lodging risk while maximizing yield and protein potential of spring wheat in the eastern Canadian Prairies. [Doctoral Dissertation, University of Manitoba]. FGS – Electronic Theses and Practica, University of Manitoba Institutional Repository. Agronomic practices to minimize lodging risk while maximizing yield and protein potential of spring wheat in the eastern Canadian Prairies

Manitoba Agriculture. (2025). Spring Wheat Production and Management. Manitoba Agriculture. Province of Manitoba | agriculture - Spring Wheat

Manitoba Agriculture. (2025). Reward Versus Risk: Seeding Early in Manitoba. Manitoba Agriculture. Province of Manitoba | agriculture - Reward Versus Risk: Seeding Early in Manitoba

Mehring, G. (2016). Determining Optimum Seeding Rates for Diverse Hard Red Spring Wheat (Triticum Aestivum L.) Cultivars. [Doctoral Dissertation, North Dakota State University]. NDSU Theses and Dissertations. Determining Optimum Seeding Rates for Diverse Hard Red Spring Wheat (Triticum Aestivum L.) Cultivars

Otteson, B.N., Mergoum, M., Ransom, J.K., & Scgatz, B. (2008). Tiller contribution to spring wheat yield under varying seeding and nitrogen management. Agron. J. 100, 406-413. doi:10.2134/agronj2007.0109.

Slafer, G.A., Savin, R., & Sadras, V.O. (2014). Coarse and fine regulation of wheat yield components in response to genotype and environment. F. Crop. Res. 157, 71–83. Elsevier B.V. doi:10.1016/j.fcr.2013.12.004.