Soil Temperatures for Cotton Planting
Planting in our region is often related to soil moisture availability in the seeding zone. This is obviously the prime consideration in many locations. Seed germination is favored by high soil oxygen concentration, adequate soil moisture, and soil temperatures above 64oF. Based on work conducted by USDA-ARS researchers at Lubbock, the cotton plant requires more than 100 hours above 64oF at the seed level to emerge. Germination can begin when the mean daily temperature is 60oF at seeding depths, but growth will be slow at these temperatures.
The optimum planting target is to have a 10-day average soil temperature of 65oF at the 8-inch depth. If poor quality seed is planted, then 70oF may be a better target. This volume of soil underneath the seed can act as a potential short-term heat buffer to moderate seed zone temperatures if cool spells do occur after planting. This is due to the fact that soil temperatures in the seed zone will lag air temperatures by about 3-5 hours.
At a minimum, soil temperatures in the seed and root zone should exceed 60oF AND the five day forecast for daytime maximum temperatures should exceed 80oF. Additionally, nighttime minimum temperatures should be forecast to be above 50oF for the next 5 days.
During critical germination times, soil temperatures below 50oF can cause chilling injury and result in malformed seedlings, reduced vigor and stand establishment, and increased likelihood of seedling disease problems.
Emergence will generally occur after accumulation of 60-80 DD60 heat units after planting. If as few as 25 heat units are forecast over the next five days, it is not recommended to plant. At Lubbock, the long-term average air temperatures and corresponding DD60s for various dates in May are listed below:
| Day | High | Low | Average | DD60s per day (=Average Temp - 60) |
| May 1 | 79 | 51 | 65 | 5 |
| May 10 | 82 | 54 | 68 | 8 |
| May 20 | 84 | 57 | 70.5 | 10.5 |
| May 30 | 87 | 60 | 73.5 | 13.5 |
When considering long-term average temperatures for May, one should consider waiting until after at least May 1 to plant. By delaying planting until May 10, at least 8 DD60s per day would result in a total of about 40 over the next five days.