Cotton Recovery to Early Season Nitrogen Stress.

Cotton is a crop globally known for fiber, protein, and oil production. Nitrogen (N) fertilizer plays a large role in its growth and development, but if poorly managed can cost producers money and pollute the environment. Studies to estimate lint yield using mid-season NDVI readings have been carried out in the past, with positive responses.  However, accurate N recommendations based on biologically functional algorithms depend upon the ability of cotton to recover from early season N stress.  This study was conducted to evaluate the ability of cotton to recover from early season N stress and to determine to what extent N application can be delayed while still producing maximum yields. The evaluation of cotton’s ability to recover from early season N stress was investigated at the R.L. Westerman Irrigation Research Facility near Stillwater, Oklahoma on a Port-Oscar silt loam (fine-silty, mixed, super active, thermic Cumulic Haplustolls), and at the Southwestern Research Station near Altus, Oklahoma on a Hollister silty clay loam (fine, smectitic, thermic Typic Haplusterts).  Preplant N was applied as urea (46-0-0); while topdressed N was applied as urea ammonium nitrate (UAN, (28-0-0).  Top-dress rates were applied at different growth stages.  Optical sensing including GreenSeeker readings of  normalized difference vegetative index (NDVI) at 3 growth stages. Cotton was harvested at maturity and lint yields calculated.  Results will include sensor correlation with plant biomass, yield, and the efficacy of sensor based N rate recommendations.
Key words: Cotton, Early season N stress, Recovery, NDVI, lint yields