By Jonathan Kleinjan
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.
1. 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.
2. 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.
3. 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.
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