Cotton has a great ability to overcome many stresses and produce profitable lint yields when the crop gets off to a good, uniform start. So, when is the “best” time to plant cotton to meet those criteria?
First, much as with corn, the goal is to achieve an acceptably uniform and optimal stand. The recommended window for cotton planting is relatively narrow compared to that for other summer crops grown in Kansas – roughly May 1 through June 5. However, it is best to monitor soil conditions rather than the calendar. For a variety of reasons, including seedling chilling, potential herbicide injury, thrips and seedling diseases, it pays to plant when growers can not only get an adequate stand, but also when the crop will grow vigorously.
Soil temperature and the 10-day forecast are two major factors to that fast start. Cotton seed germination and early growth/emergence is favored by soil temperatures above 64 degrees F and adequate, but not excessive, soil moisture. Based on USDA-ARS research work at Lubbock, TX, the seedling cotton requires more than 100 hours above 64 degrees F at the seed level to emerge. In Kansas, we often use 60 degrees F as our baseline temperature at seed level. In addition, growers should be planting high quality varieties (e.g. high cold germination and large seed size, with good cold tolerance and early season vigor ratings).
Information from North Carolina State University’s cotton web page illustrating the importance of heat unit accumulation immediately following planting is shown in Table 1.
Table 1. Relationship between predicted DD-60s and Planting Conditions (Source: North Carolina State University, https://cotton.ces.ncsu.edu/
Predicted DD-60 accumulation for five days following planting
10 or less
11 – 15
16 – 25
26 – 35
36 – 49
Avoid planting cotton if the low temperature is predicted to be below 50°F for either of the two nights following planting or predicted daily DD-60s is near zero for the day of planting.
Cotton seed subjected to cold the first 2-3 days after planting, OR when the seed is imbibing moisture from the soil, is susceptible to imbibitional chilling injury. Cotton seed contains lipids which must be converted to energy, and cell membranes must develop properly. If soil temperatures drop below 50 degrees F during this critical germination period, seedlings may suffer damage. The first 30 minutes after planting, the seed will absorb up to 60% of the water necessary for germination. Cold soil temperatures (<45°F to 50°F) will most likely lead to injury or seedling death. Damage may result in malformed seedlings, loss of or damage to the taproot, and a greater likelihood of seedling disease problems. Injury usually kills the root tip meristematic tissue which stops normal taproot growth and leads to lateral root development (Figure1). If the plants survive, the root system will not develop normally.
Figure 1. Cotton seedlings subjected to chilling temperatures (A) compared to seedlings not chilled (B) during imbibition from a study conducted by Hopper and Burke. Note the absence of normal taproot growth of the seedlings in A. Seedlings in A and B were exposed to the same temperature (86°F) with the exception of the first six hours of imbibition in which seedlings in A were exposed to chilling temperatures of 40°F.