We’re seeing some fields showing some nutrient issues which have reached 6th week of bloom. The field above had the red tint similar to potash deficiency in which we decided to run a leaf tissue and petiole sample. Everything actually came out good except nitrogen. UGA Extension Fertility Specialist Dr. Glen Harris says we generally do our leaf tissue samples before bloom and petiole following bloom. When one is taken this much after bloom it can be difficult pin pointing issues, especially nitrogen.
We were not much under nitrogen uptake, but was still puzzling since a normal recommendations were applied. We are now at 8th week of bloom, and at this time no foliar applications would economically improve the situation. There is always discussion about waiting on bolls in the upper portion of the plant. Dr. Harris says, “Based on field research trials, foliar fertilization is most effective when applied during peak bloom or the first 4 weeks of bloom. Foliar feeding during the 5th – 7th week of bloom may or may not be effective depending on the particular cotton variety. Once you pass the 8th week of bloom, it is too late and no foliar feeding is recommended.”
It is difficult to determine fertility problems in fields were we rotate in and out each year. In the case where we are in the same field for subsequent seasons, we can make changes to our fertility program. increase our total N inputs to prevent the same issue. But even a slight increase or decrease in something like N, we still have to think about how more or less rainfall can affect outcome.