Cotton Fertilizer Information
Cotton planting is scattered across our planting window. Abundant rainfall has hampered and or prevent entry to many infield procedures this year. Please refer to the 2021 UGA Cotton Production Guide here https://www.ugacotton.com/production-guide/ for details. Sidedress N between first square and first bloom depending on growth and color (toward first square if slow growing and pale green, toward first bloom if rapid growth and dark green). A portion of the sidedress N can also be applied as foliar treatments or through irrigation systems. No N should be soil-applied (either top dressed or through the pivot) after the 3rd week of bloom.
Studies have shown that uptake of soil-applied N from by cotton roots is basically ineffective after this critical point.
Foliar Fertilization
Foliar fertilization of cotton should be used to supplement a good soil-applied fertilizer program. The most likely nutrients needed for foliar applications are N, B, and K. Foliar N applications can be made as part of an overall N management strategy or as determined by petiole testing. Feed grade urea is the most reliable, economical, and proven foliar N material. The standard recommendation is for 4.5 lb N/A as urea in 5 gal or more of water (5gal/A assumes aerial application). Both liquid (23 % N) and granular urea (46 % N dissolved into water) can be used. Applying all the recommended K to soil preplant or at-planting should provide sufficient K for Georgia cotton in most cases. Potassium nitrate is the most common material used for foliar K applications. The standard recommendation is for 4.4 lb K2O /A in 5 gal or more of water. Again, 5 gal/A assumes aerial application and both liquid and granular KNO3 can be used. If potassium nitrate is not available, there are other foliar K fertilizers available (for example, liquid 5-0-20) that
can also be used to foliar feed K. However, many of these materials do not contain as much K and cannot be applied at rates comparable to potassium nitrate without causing significant leaf burn.
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 grown. How late is too late to foliar feed cotton? Once you pass the 8th week of bloom, it is too late and no foliar feeding is recommended.