Wheat planting conditions as of late-September 2018
September has returned to a wetter pattern in the west (Figure 1). In the majority of the wheat growing region of the state, namely central and western Kansas, this was accompanied by warmer than normal temperatures and windy conditions. Therefore, estimated root zone soil moisture is relatively low in the west as compared to eastern Kansas (Figure 2).
Figure 1. Total cumulative precipitation in the period between September 19 and 25, 2018. Map by K-State Weather Data Library.
Figure 2. Measured surface soil moisture in percent of soil volume as of 27 September 2018. Map by Kansas Mesonet.
The weekly precipitation forecast for Kansas indicates that the probability of precipitation for the next 7 days exists for totals ranging from 0.1 inches in western Kansas to as much as 1.75 inches in the eastern portion of the state (Figure 3). Despite the drier profile in western Kansas, the forecast is favorable and might bring much needed moisture for a good start to the wheat-growing season.
Figure 3. Weekly precipitation forecast as of September 28, 2018 by the National Weather Service Weather Prediction Center (NOAA). Precipitation probabilities in Kansas for the next 7 days’ range from 0.10 to 1.75 inches.
Possible challenges for wheat planting and crop establishment
The current wheat planted acreage in Kansas, according to the USDA-NASS crop progress report, was 21% as of September 28. This is slightly below the 1994 – 2016 average of 30% (Figure 4), and the crop might be favored by the forecast rain.
Figure 4. Percent wheat area in Kansas planted by as function of time; starting September 1. Purple area and solid line show the long-term range and average, and the dotted line shows 2018 progress. Data shown for the period 1994 – 2018 as reported by the USDA-NASS Crop Progress Reports (https://www.nass.usda.gov/Publications/National_Crop_Progress/).
One challenge that fields already planted can face is high soil temperature stress, which can lead to germination problems especially in wheat varieties with high-temperature germination sensitivity (varieties that will not germinate when soil temperatures are greater than 85 degrees F). Average weekly 2-inch soil temperature during September 22-28 ranged from 64 to 72 degrees F (Figure 5). Earlier planted wheat likely encountered soil temperatures above 85 degrees F resulting in poor germination due to hot soil temperatures. Sufficient rainfall event will continue to decrease soil temperatures and germination should occur.
Figure 5. Weekly average 2-inch soil temperature during the September 22 – 28 period. Map by Kansas Mesonet.
With about 80% of the winter wheat area still to be planted, the crop sowing progress in the following days will depend on weather conditions. While many producers might try to plant some acres before the forecast rain, a delay in planting progress can be expected after the rains, especially in central Kansas, depending on total precipitation and soil moisture conditions.
If precipitation is excessive, producers should not hurry and sow wheat into extremely moist soils. Planting wheat under wet conditions can present either mechanical or biological challenges.
Mechanical challenges include:
- Inability to get the equipment in the field to perform plowing or sowing operations.
- Mudding up the equipment after field operations are started.
- Increased soil compaction due to machinery traffic in moist soils. Soil compaction can restrict adequate root growth, affecting plant anchorage and decreasing its ability to uptake water and nutrients.
Biological challenges include:
- Delayed crop emergence due to wet and cold soils.
- Possibly increasing early-season disease and insect problems.
Planting wheat into a dry topsoil can also be challenging. While a good seed distribution is generally achieved when sowing wheat into dry soils, if the forecast rain does not materialize, the lack of moisture for germination can result in uneven stands and high within-field stand variability (Figure 6), which can ultimately impact grain yield. Otherwise, the forecast rain will help ensure a good stand establishment.
Figure 6. Uneven wheat stands resultant from sowing into dry soils. Photo by Romulo Lollato, Extension wheat and forage specialist.
Even in late September, we are still in the optimum planting date range for wheat for most of the state, so producers should not hurry and sow wheat into extremely moist soils. Waiting for the water to drain and/or evaporate so the soil dries adequately before performing the sowing operation would be the best option.
Romulo Lollato, Wheat and Forages specialist
Mary Knapp, Weather Data Library
Andres Patrignani, Soil Water Processes Agronomist