As our cotton is progressing, we are approaching peak bloom on some of our oldest cotton. This is the time when many growers will begin to apply foliar fertilizer to their cotton, usually nitrogen or potassium. Foliar fertilizer is used to supplement a good soil applied fertilizer program. Some growers may automatically apply foliar fertilizer to their cotton, or use it in instances where they think additional nitrogen or potassium is needed on the crop.
Here’s the UGA recommendations for applying foliar fertilizer to cotton:
Nitrogen: Feed grade urea is the most reliable, economical and proven foliar N material. The standard recommendation is to apply 4.5 lbs of nitrogen/acre as urea in at least 5 gallons or more of water per acre (5 gal/acre assumes aerial application, 10 to 12 gallons of water is preferred for ground application). Both liquid urea (23% N) and granular urea (46% N dissolved into water) can be used.
10 lbs of feed grade urea (granular 46% N) per acre will give you approximately the recommended 4.5 lbs of nitrogen per acre.
Potassium: Potassium nitrate is the most common material used for foliar K applications. The standard recommendation is to apply 4.4 lb of potassium per acre in 5 gallons or more water per acre. (Again 5 gallons assumes foliar application, 10 to 12 gallons is preferred for ground application). Both liquid and granular potassium nitrate can be used.
10 lbs of granular potassium nitrate (44% K2O) per acre will give you the recommended 4.4 lbs of potassium per acre.
Keep in mind that there are other products out there available to use for foliar feeding cotton. Some of these may not contain as much fertilizer as the products mentioned above and you may not be able to apply them at the same rates as mentioned above. Use caution with all fertilizer products as improper rates could cause leaf burn.
How late is too late to foliar feed cotton?
Foliar feeding is most effective when applied during peak bloom, or the first 4 weeks of bloom. Foliar feeding during weeks 5-7 of bloom may or may not be effective depending on the variety grown.
Once you pass the 8th week of bloom, it is too late. No foliar feeding is recommended after this point.