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Evaluation of Variable Rate Pix (Mepiquat Chloride) Application by Soil Type

Mary E. Thurman and Ronnie W. Heiniger


 
ABSTRACT

Growth variability, due to soil type, moisture or fertility differences, is common in many fields across the Cotton Belt. Pix (Mepiquat Chloride) is used for height control during the growing season. The objectives of this study were to evaluate the ability of a variable rate Pix application by growth areas to a) reduce variability in final plant height, b) increase yield, and c) reduce overall use of Pix in variable cotton fields. A split plot design was used with four Pix treatments: untreated, uniform rate, variable rate based on the rapid growth area, and variable rate based on the slower growth area. Both growth area specific variable rate treatments resulted in reduced variability in final height and plants within the ideal range on 32"-40". On the rapid growth soil type, the variable rate treatment resulted in higher Pix rates, yields, and boll retention than the other treatments for this soil type. When yield data were averaged over two locations, the VRT treatment in the rapid growth soil had a 65.8-pound advantage over the uniform Pix treatment. The VRT treatment in the growth limiting had a 45.3-pound lint advantage over the uniform rate. An economic analysis was performed and yield numbers were applied to a 45 acre variable field (approximately 75% rapid growth soil type, 25% growth limiting). In this situation more Pix would have been recommended by VRT than uniform; however the grower would have still found a yield advantage equivalent to $1540 through variable rate Pix use.



Reprinted from Proceedings of the 1999 Beltwide Cotton Conferences pp. 524 - 526
©National Cotton Council, Memphis TN

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Document last modified Monday, Jun 21 1999