Foliar application of urea to cotton (Gossypium hirsutum L.) is a widely used practice in the Cotton Belt, but there is a lack of published information concerning the utilization of this urea by the cotton plant. A field study using Stoneville 506 was conducted to (1) investigate the uptake and translocation of foliar applied (15)N-urea within a representative sympodial branch as well as the remainder of the plant at specific time intervals after application, and (2) to evaluate the effects of different tissues and tissue age on the efficiency of uptake of foliar-applied N.

Foliar-applied urea was rapidly absorbed by the sympodial leaf and translocated into the subtended boll as well as the next boll along the branch within 6 to 12 hours after application. Absorption into the leaf occurred within one hour after application, but this varied depending on environmental conditions as well as the condition of the plant. No translocation of (15)N occurred to the main-stem leaf or the second sympodial leaf along the branch. Both tissue type and tissue age had little effect on N absorption. The location of the foliar-N spray within the canopy affected the uptake and yield. The benefits of late season foliar applications were discussed.