Study suggests West Texas cotton farmers should apply more potassium to soil

Cotton farmers in West Texas could be missing out on increased yields by not applying enough potassium, or K, to their soils, according to recent research. 

A new study conducted by researchers at the Texas A&M AgriLife Research and Extension Center in College Station has shown that, despite the region's already-high soil potassium levels, fertilizing with potassium can result in significant yield increases. 

Amee Bumguardner, Katie L. Lewis, Seth A. Byrd, Glen Ritchie, and Gaylon Morgan teamed up for study. They were looking to determine the effects of potassium fertilizer on cotton growth, yield and fiber quality in semiarid conditions.

Researchers used muriate of potash (KCl) applied through knife-injection and broadcast methods. Potassium application rates included 0, 45, 90, 135, and 180 kg ha-1 with both high (90% ET) and low (30% ET) irrigation levels. Leaf K concentrations were also measured to determine potassium's effects on cotton growth. 

The research could provide a valuable insight into the effects of K application on cotton yield in semiarid conditions. 

"Potassium did not offset the negative effects of moisture stress on cotton lint yield in the semiarid environment of the Texas High Plains," the researchers concluded. "Although a positive lint yield response to added fertilizer K given that soil test levels were greater than the Mehlich III K critical level were not expected, a positive response due to K fertilizer application on lint yield following broadcast and injection applications across irrigation level was observed at Lamesa in 2016."

Researchers conducted field trials in the Texas communities of Lamesa and New Deal to assess the impact of potassium application under varying irrigation levels. 

They found that in Lamesa in 2016, lint yield was significantly higher when 90 kg K ha-1 was broadcast, (2,153 kg ha-1 lint) compared to the 180 kg K ha-1 treatment and all treatments with 30% ET irrigation. However, in 2017, no lint yield differences were observed among potassium application rates. 

At New Deal, lint yield was similar across all K application rates in both years. While potassium application increased yield with the 90% ET irrigation level with broadcast application, no differences were observed in water-deficit cotton, suggesting the need for further research to better understand the dynamics of potassium on lint yield in semiarid cotton production systems.

The study also evaluated whether potassium application increases crop growth, yield and fiber quality in soils. 

Results showed positive responses in cotton yield were observed when soil potassium was applied, but only when applied at the appropriate rates. Furthermore, no significant effects of potassium application were observed on fiber quality traits. 

The findings contradict the common notion that potassium applications are not required in soils with sufficient K levels, highlighting the importance of site-specific fertilizer recommendations. Researchers suggest that potassium application rates should be based on yield potential, soil characteristics, and management practices.

The study, "Potassium Fertilization Effects on Cotton Growth, Yield, and Fiber Quality Under Varying Irrigation Regimes," was published in the Journal of Cotton Science. The research was funded by the Texas Cotton Producers Board and Cotton Inc.