Corn planting and soil temperatures: Late-March and projected conditions
Corn planting time is here, or nearly here. Soil planting conditions are critical for successful emergence and early-season uniformity of the crop. In making this decision, producers should not only consider the optimal soil temperature for adequate emergence but also soil moisture conditions at planting.
Soil temperature conditions for the past week (March 15-21) experienced minimal changes in the SE and NE regions of the state, ranging from 49-51 F for the SE to 43-46 F for the NE and NC regions (Fig. 1). Average soil temperatures varied from 43 F (minimum) to close to 59 F (maximum) for this period. The warmest soil temperatures were in the SW and southern section of the SC region. As reflected in the Figure 2, a large soil temperature increase occurred in the western part of the state – with temperatures increasing approximately from 4 to 8 F compared to the previous week. Soil temperature increases were reported in all districts, but lower increases were reported in the NC, NE and SE regions.
As a reminder, selection of the optimal planting date is one of the most critical factors in the farming decision-making process. In making this decision, producers should consider soil temperatures rather than just the calendar dates. Changes in soil temperature will be also affected by changes in soil moisture.
Figure 1. Average soil temperatures at 2-inches for the week of March 15-21, 2017.
Figure 2. Changes in weekly average soil temperatures at 2-inches week ending March 14 vs. week ending March 21.
The precipitation outlook for the coming 7 days (March 24-31) is projecting between 1 to close to 4 inches depending on the area of the state (Fig. 3). Larger precipitation amounts are forecast for the eastern and SC parts of our state – between 2.5 to 4 inches; while less than 1.5 inches is projected for the western, NC, and NW parts of the state.
Figure 3. 7-Day Outlook Precipitation Probability from March 24-31, NOAA.
Many factors, including amount of residue coverage, soil moisture, and topographic position will impact the actual change in soil temperature in any given field. Wet soils in a no-till situation will be slower to warm. Dry soils will vary more rapidly, matching air temperatures.
Projections for coming weeks are for precipitation and temperature to be above normal for almost the entire state (Fig. 4), which will slow down soil warming conditions. Also, soil moisture content will impact the workability of those fields for planting.
Figure 4. 8-14 Day Outlook temperature (upper panel) and precipitation (lower panel) probability from March 31-April 6, NOAA.
As a reminder optimal soil conditions produce a large impact on corn uniformity and early growth. Lack of uniformity in emergence can greatly impact corn potential yields.
Temperatures at or above 55 F will help establish the young corn plants and improve the probability of presenting a uniform canopy. Proper soil moisture conditions will be needed to avoid potential problems related to wet soils, such as having plants with shallow root systems, which can increase susceptibility to standability problems during the growing season.
Think about all these factors when deciding on the optimal planting time. Wet conditions seem likely to affect early planting for corn in many areas of the state. If possible, wait and plant under more uniform soil temperature and moisture conditions to guarantee a more uniform early-season stand of plants. More information about planting status of summer row crops will be provided in upcoming issues of the Agronomy eUpdate. Stay tuned!
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Mary Knapp, Weather Data Library