Precision farming is a management method that takes advantage of Global Positioning Systems and Geographic Information Systems to optimize crop productivity at any point in the field. The use of this technique requires knowledge of the spatial variability present in a field, and equipment capable of applying production inputs at variable rates. We propose the use of plant height as a surrogate variable to assess growth potential within a production field. Plant height is an important integrator of the production environment and can be used to identify areas of the field with production problems. This study used spatial variability in plant height of a cotton field at Kingsville, Texas for the application of mepiquat chloride (Pix). The MEPRT software was used to develop a relationship between plant height and pix application rate. The coefficient of variability in plant height was reduced from 12.2% on May 29, prior to the application of Pix, to 7.9% on June 16. The amount of pix applied ranged from 4 to 8 oz per acre, with a mean of 6.0 oz per acre. Although the yield increments due to the variable rate application of pix were negligible, the improved uniformity of the field may benefit from the application of harvest aid chemicals and harvest efficiency. We concluded that further evaluation of the economic benefits of variable rate pix application in rain-fed areas are needed to determine the usefulness of Variable Rate Application Systems (VRAS) in South Texas.