Evaluation of Cotton Yield, Quality, and Plant Growth Response to Soil-applied Potassium

The frequency and severity of K deficiency symptoms in crops grown on the clay soils of the Central Blacklands and Gulf Coast regions of Texas have increased in recent years. While drought has contributed to the occurrence, the frequency of K deficiencies in multiple row crops, especially cotton, is a major concern to producers, scientists, and other agricultural professionals. The objective of this research is to evaluate the effect of K application rates and methods on cotton growth, development, yield, and fiber quality.

Studies were conducted in 2013 and 2014 at a total of eight sites in the Central Blacklands and Gulf Coast regions of Texas. Sites were in Williamson, Hill and Wharton counties. Soil test K concentrations ranged from 60 and 350 ppm. Five rates of banded liquid K (20, 40, 80, 120, and 160 lb K₂O/A as 0-0-15, KCl) and four rates of granular broadcast K (40, 80, 120, and 160 lb K₂O/A as KCl) were evaluated. The liquid treatments were banded preplant approximately 4 in. to the side of the row and 6 in. deep. Granular (dry) treatments were broadcast preplant and lightly incorporated. A zero K control was included. Phosphorus and N were applied according to soil test results for a 2 bale/A (lint) yield goal. In-season plant measurements included stand counts, plant height, nodes to first fruiting branch, and total nodes. Lint yield was determined and samples sent to Cotton Inc. for HVI (quality) analysis.

In 2013 there was response to K application, with band applied K performing better than broadcast application. However, in 2014 K application did not produce significant difference in yield at any site, regardless of rate or placement. This effort is planned for expansion in 2015 to other cotton-producing regions of the USA, with industry and commodity group support.