Evaluation of Cotton Yield, Quality, and Plant Growth Response to Soil-Applied Potassium
The frequency and severity of potassium (K) deficiency symptoms in cotton have increased in some soils in the US Cotton Belt over the past decade or so. Insufficient levels plant available K in these regions are likely decreasing yields and fiber quality and leading to decrease profits for cotton producers.
IPNI-2015-USA-101
29 Apr 2016
2015 Annual Interpretive Summary
A previous study was conducted by Texas A&M University (TX-56) in response to increased frequency and severity of K deficiency symptoms in cotton grown on certain soils. The initial Texas project gained considerable interest among cotton specialist from other states in the U.S. Cotton Belt. Thus, in 2015 the study was extended across 11 Cotton Belt states with support from multiple sources (Cotton Inc., IPNI, and Fluid Fertilizer Foundation). The objective of this multi-state study is to evaluate the impact of K fertilizer placement and rate on cotton lint yield, quality, and return on investment, and to re-evaluate and modify K fertilizer recommendations accordingly.
In 2015, a total of 14 sites were spread across 11 states—Alabama, Arizona, Arkansas (2), Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas (3), and Virginia. Soil samples were collected prior to planting at all sites in increments of 0 to 6, 6 to 12, and 12 to 24 in., and subsequently analyzed by the Texas A&M Soil Testing Laboratory. Fertilizer was applied 2 to 4 weeks prior to planting. Potassium fertilizer application rates were 0, 40, 80, 120, and 160 lb/A. Placement comparisons were broadcast incorporated versus banding (6 in. deep, 4 in. to side of row). For the broadcast application granular KCl was used, and for the banded treatment solubilized KCl was used. The need for other nutrients was addressed according to soil test recommendations. A single cotton variety (DeltaPine 1321B2RF) was used at all locations to eliminate the effect of genetics on yield and quality parameters.
At the time of this report only yield data from the sites was available, lint quality and leaf tissue data were still being compiled. Lint yield response in 2015 was mixed, with little apparent relationship between soil K level and K fertilizer response, and no clear pattern of response to placement. In some cases there were numerical, but not significant responses to K rate and placement, and unexpectedly there was significant yield response to banded K at the higher application rates at the site with the highest preexisting soil K concentration (Lubbock, 350 ppm K, Mehlich III). This is the first year of a project that is planned for three years.