Cotton doesn’t like it when it’s cold, so plant when it’s warm.
- How cold is too cold for cotton? Chilling temperatures are less than 50 °F but above freezing. These temperatures can kill or severely injure a developing seedling if experienced during early germination and will slow plant growth more than predicted by DD60 accumulation when experienced after emergence. Check the forecast for your region prior to planting.
- What are the ideal temperature conditions for planting? The current recommendation is for planting to occur when soil temperatures are 65 °F or above for three consecutive days and when 50 DD60s are projected to accumulate within five days after planting. These conditions are conducive to rapid germination and vigorous seedling growth, which has the added benefit of decreasing the damage that can be done by early-season pests.
- What’s a DD60? This is the number of degree days accumulated over a particular period of time. The most simplistic formula for calculating daily DD60s is as follows:
DD60 = [(Tmax + Tmin)/2] – 60 °F
Other approaches to DD60 calculation also set an upper-temperature threshold or a daily limit of 10 DD60s. DD60 calculators are available at http://www.georgiaweather.net.
Too much or too little water limits stand establishment.
- Too much water? I’m talking about waterlogging here. Oxygen is a requirement for growth during the germination phase, so waterlogging suffocates plants by creating anaerobic conditions. Having a well-aerated seed bed and avoiding excessively wet soil conditions via proper planting date selection and knowledge of field history can help lessen these problems.
- Too little water? The cotton seed contains a desiccated embryo that is ~8-10% moisture, which is substantially drier than other tissues on a fully-grown cotton plant (80-90% relative water content for leaves). As a result, the cotton seed readily takes up water from the surrounding soil even if the water content of the soil is low. This can be problematic if the soil profile has a relatively low soil water content at planting because the seed is more susceptible to dehydration stress after embryonic tissues have been hydrated. Obvious remedies for this situation include post-planting irrigation for fields in which irrigation is available or planting into good soil moisture for dryland fields and knocking beds down at planting to minimize water loss from the upper portion of the soil profile before harvest. Planting depth affects moisture availability too. The current recommendation in Georgia is to plant the seed at a 0.5 to 1-inch depth. Deeper planted seeds have access to more soil moisture, but the risk of stand loss increases with depth, so planting a variety with high seedling vigor may be necessary for these instances.
If you’ve got crusting, get a rotary hoe soon.
- What is crusting? Crusting is when a thin compacted soil layer forms over a field. This is a problem because the cotton seedling often cannot exert enough pressure to break through the crust.
- When should a rotary hoe be used? A rotary hoe would only be used where crusting was a widespread issue in the field, but timing matters. As a general rule, a rotary hoe should be run within 10 days after planting to ensure that plants don’t just sit under the soil surface and rot. However, I have also had good luck using a rotary hoe as late as 15 days after planting, provided the seedlings I dug up exhibited normal development (a well-developed seedling radicle, pronounced hypocotyl hook, and no visual evidence of disease). The best thing to do is dig up some plants and see what you’re dealing with before making the decision to use a rotary hoe.