The 2017 winter wheat crop in Kansas started out with the unusual challenge of excessive moisture conditions during the optimum sowing window. As a consequence, wheat sowing was delayed for a large portion of the state until mid-October. Afterwards, temperatures have been below-average, thus slowing down crop development. What are the consequences of the delayed sowing progress and below-average temperatures?
Winter wheat sowing delay for 2017-18
Not much of the wheat area was planted before the late-September/early-October rains started as the majority of Kansas was relatively dry. The USDA estimates of crop progress indicated 14% of the Kansas wheat crop was planted by Sept 24 and 21% was planted by October 1st, roughly when the majority of the rain started. Thus, about 21% of the crop was planted before the rain. These early-sown fields had issues with excessive precipitation, which led many producers to replant, especially in low-lying areas that were water-logged and had large drowned out spots. By October 15, wheat in the state of Kansas was only 42% planted as compared to >70% for the same period historically, which provides some perspective on the degree of sowing delay. (Figure 1). As of early November, the majority of the crop has been sown and Kansas is close to the historical normal.
Figure 1. Wheat sowing progress in Kansas during 2017 (dashed line) as compared to the 1994 – 2016 average (solid line) and range (purple area). Wheat sowing progress in 2017 was the slowest since 1994, considerably below the range observed in the period. Graph based on USDA-NASS crop report of progress as of November 16, 2017.
Crop development for the Kansas winter wheat crop
Early-sown wheat fields were subjected to water logging and in many cases required re-planting portions of the field. Wheat fields planted after mid-October have been facing cooler-than-normal temperatures since the time they were sown, as well 30+ days without significant precipitation in many parts of the state, which has slowed crop development. Therefore, the majority of the Kansas wheat crop does not have much fall growth or tillering at this point (Figure 2). The forecast for the later part of November is warmer-than-normal temperatures, which might help the crop produce some extra tillers before the onset of winter, and in many situations be favorable to help with winter survival. Soil moisture increases tillering and winter survival, while a dry topsoil would reduce tillering and increase susceptibility to freeze damage.
Figure 2. Wheat plants sown in mid-October at the three-leaf developmental stage as of Nov. 13, 2017. At this stage, the first tiller has already started to develop but might not yet be visible. If temperatures had been warmer in late October /early November, these plants could potentially be producing their second or third tiller. However, below-average cool temperatures delayed wheat development. Ideally, these plants need to produce an additional 3-4 tillers before the onset of winter dormancy to maximize cold hardiness. Photo taken near Hutchinson by Guilherme Bavia, visiting scholar at K-State Wheat and Forages Production Team.
Delayed sowing and wheat yield potential
Generally, delaying wheat sowing date past the optimum window causes the wheat yield potential to decrease (Figure 3). However, if weather conditions are optimal (mild winter, and cool and moist spring), the crop might still result in decent yields. Reasons for the generally observed decreased yield potential with a delay in sowing date include:
- Less fall tillering potential: fall-formed tillers are generally more productive than spring-formed tillers. When wheat is sown late, it will have less time to tiller in the fall, which decreases the production of higher yielding tillers as well as total tiller production.
- Delayed cycle: late sowing often delays the entire crop cycle as compared to a crop sown earlier. As a consequence, the grain filling period might occur a few days later and under hotter air temperature conditions, which decreases yield and test weight.
- Greater exposure to winterkill: a wheat crop with 3 – 5 fall-formed tillers has greater cold tolerance than a crop that has only one or two tillers. As a consequence, late-sown fields might be more exposed to winterkill, especially in dry conditions. Winterkill is discussed in more detail in the accompanying article in this current eUpdate issue.
Research conducted by Merle Witt with late-sown wheat in Garden City during 1985 through 1991 is summarized in Figure 3. Averaged across all these years, delaying wheat sowing from October 1 to November 1 delayed heading date by 6 days and decreased wheat yields in 23%. Grain filling period was progressively shortened in about 1.7 days and occurred under hotter temperatures (about 1.5 degrees F) for every month of delay in sowing date.
Figure 3. Wheat grain yield, test weight, and heading date responses to sowing date between 1985 and 1991. Data adapted from Kansas Agric. Exp. St. SRL 107.
Therefore, the potential consequences of the delayed progress of the Kansas wheat crop during October include greater exposure to winterkill (especially in dry soil conditions with little snow cover – see accompanying eUpdate article for more details), delayed crop cycle for grain filling under warmer conditions, and a lower yield potential due to decreased fall tillering.
Yet more importantly is the favorable fall precipitation which has allowed the wheat crop to become established. Even if planting and emergence are delayed a few weeks later than optimal, the precipitation that was received in October is setting the 2018 wheat crop up better than had conditions been dry and wheat emergence delayed or prevented due to dry soil conditions. Particularly in the western half of Kansas, research evaluating effects of weather conditions on long-term variety performance tests indicated that wheat yields were influenced the most by favorable precipitation conditions during the fall that promoted stand establishment and moist soil conditions (Holman et al. 2011).
Holman, J.D., A.J. Schlegel, C.R. Thompson, and J.E. Lingenfelser. 2011. Influence of Precipitation, Temperature, and 56 Years on Winter Wheat Yields in Western Kansas. Crop Management 10(1), available at: https://dl.sciencesocieties.org/publications/cm/abstracts/10/1/2011-1229-01-RS
Romulo Lollato, Wheat and Forages Specialist
lollato@ksu.edu
John Holman, Cropping Systems Agronomist, Southwest Research-Extension Center
jholman@ksu.edu
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