Post-bloom Nutrient Deficiencies, Waterlogging, and Foliar Feeding (Glen Harris): Most Georgia cotton has been blooming for a while now and is starting to show some classic post-bloom nutrient deficiencies. Some areas of the state have gotten significant rainfall also and are showing symptoms of waterlogging or “wet feet”. Sometimes these symptoms, usually involving yellowing or bronzing of leaves, can be confusing and hard to diagnose. Knowing which problem you are dealing with is critical to knowing how or even if you can remedy the problem. Taking soil and tissue samples from “good” and “bad” areas of a field can go a long way toward deciding which nutrient problem you have if any. Petiole sampling is a good way to determine N and K status and needs post-bloom but will not pick up problems such as sulfur and magnesium deficiency (have to take tissue or “leaf blade” samples), Also, once cotton has been blooming for a full 3 weeks, it is not recommended to soil-apply nitrogen (and definitely not K) with ground rigs or through center pivots since root systems are declining and uptake from the soil will be very inefficient. It is at this point (after 3 weeks of bloom) that foliar feeding things like N and K should be considered. 

Here is a quick look at symptoms of some of the post-bloom problems occurring in Georgia cotton right now: 

Nitrogen – A pale yellowish leaf color should start on older leaves toward the bottom of the plant since nitrogen is mobile and can move to the younger leaves at the top of the plant. Early on plants can also be stunted and younger leaves may be reduced in size. Post-bloom and if nitrogen deficiency gets severe enough the bottom leaves will turn bright yellow or red. This is a sure sign of nitrogen deficiency. [READ MORE]