Recent weather pattern
The last week brought significant rains in the eastern portion of the state, with as much as 5.88 inches accumulated between September 13 and 19 (Figure 1). The majority of the wheat growing region of the state, though, namely central and western Kansas, had very limited precipitation totals, ranging from 0 to 0.14 inches. As a consequence, 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 13 and 19, 2017. Map by K-State Weather Data Library.
Figure 2. Estimated root zone (~3 ft) soil moisture in percent of soil volume as of 19 September 2017. Map by Dr. Andres Patrignani, K-State Soil Water Processes specialist.
The weekly precipitation forecast for Kansas indicates that the probability of precipitation for the next 7 days exists for totals ranging from 1.7 inches in eastern Kansas to as much as 5.7 inches in the western portion of the state (Figure 3). Despite the drier profile in western Kansas, the future 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 22, 2017 by the National Weather Service Weather Prediction Center (NOAA). Precipitation probabilities in Kansas for the next 7 days range from 1.7 to 5.7 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 7% as of September 18. This is slightly above the 1994 – 2016 average of 6.2% (Figure 4), and the crop might be favored by the forecast rain.
Figure 4. Percent wheat area in Kansas planted by September 18, 2017. Data shown for the period 1994 – 2017 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 won’t germinate when soil temperatures are greater than 85 degrees F). Average weekly 2-inch soil temperature during September 13-19 ranged from 68 to 79.1 degrees F (Figure 5), indicating soil temperatures above 85 degrees F were likely experienced. In fields currently experiencing poor germination due to hot soil temperatures, a cold rainfall event will decrease soil temperatures and germination should occur.
Figure 5. Weekly average 2-inch soil temperature during the September 13 – 19 period. Map by K-State Weather Data Library.
With 93% 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 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:
Biological challenges include:
Planting wheat into a dry topsoil, as is the condition of many parts of southwest and south-central Kansas, 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.
In mid-September, we are still in the beginning of the optimum planting date 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