Wheat yields are determined by the combination of main stem, and tillers. A tiller is a stem or shoot produced after the initial parent shoot grows from the wheat seed. Opinions vary as to whether or not more tillers are beneficial to grain yields. Tillers can be beneficial, helping a wheat plant to ‘fill-in’ areas with a poor stand and thus provide weed suppression. More tillers can also result in more heads at harvest, although most research has shown that, regardless of the number of tillers produced, 85-100% of HRSW grain yield is produced by the main stem and the T1 and T2 tillers. A review of intensive wheat management studies suggest that increased yields are the result of more primary spikes with heavier kernels, instead of increased tiller counts.
If a producer wishes to reduce the number of tillers in a wheat production field, there are several management practices which can be implemented.
- Delayed planting.
Late planting will generally result in fewer tillers due to a reduction in vegetative growth. However, wheat is a cool-season grass and is most productive when planted early. This management practice is not recommended.
- Variety selection.
There is genotypic variation for tillering capacity among cultivars. While environmental factors are typically more important than variety selection, low-tillering varieties may respond differently to other management practices than high-tillering varieties.
- Nitrogen rate and timing.
In general, more N will result in more vegetative growth and more tillers. However, tiller formation can be affected by the timing of N and can be increased when application occurs before planting or during the tillering process. To reduce tillers, the bulk of N should be applied after tillering, just prior to stem elongation. A drawback to this approach is another trip across the field and the risk of having N application delayed by weather events.
- Increase seeding rate.
Optimum seeding rates to achieve high yields can vary greatly across variety and environment. However, increasing the seeding rate seems to have the largest impact on reducing the number of tillers without negatively influencing yield. Studies involving intensive management of Hard Red Spring Wheat (HRSW) usually increase the seeding rate by ~50% (i.e. from 1.2 million to 1.8 million seeds/acre).
In a summary of intensive management research conducted on Hard Red Spring Wheat in the upper Great Plains, Ransom et al. (2007) state “It has been hypothesized that, by delaying the N application until tillering has ceased combined with a higher seeding rate, there will be more main stems, greater yield potential, and more uniformity in the flowering of the spikes”.
- Otteson, B.N., M. Mergoum, and J.K. Ransom. 2007. Seeding rate and nitrogen management effects on spring wheat yield and yield components. Agron. J. 99:1615-21
- Otteson, B.N., M. Mergoum, J.K. Ransom, and B. Schatz. 2008. Tiller contribution to spring wheat yield under varying seeding and nitrogen management. Agron. J. 100:406-413.
- Ransom, J.K., G.J. Endres, and B.G. Schatz. 2007. Sustainable improvement of wheat yield potential: The role of crop management. Journal Agric. Sci. 145:55-61.