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Title: POTASSIUM REQUIREMENTS OF ULTRA NARROW AND CONVENTIONALLY SPACED COTTON AS AFFECTED BY TILLAGE

Author
item Reeves, Donald
item MULLINS, GREGORY - VA POLYTECHNIC INSTITUTE

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/8/2002
Publication Date: 5/20/2002
Citation: Reeves, D.W., Mullins, G.L. 2002. Potassium requirements of ultra narrow and conventionally spaced cotton as affected by tillage. In: Proceedings of the Beltwide Cotton Conference, National Cotton Council, January 8-12, 2002, Atlanta, Georgia. 2002 CDROM.

Interpretive Summary: Because of higher plant populations, smaller plants with reduced root systems, and removal of a higher proportion of burs (which contain high amounts of potassium) with stripper harvesters compared to spindle harvesters, potassium fertility management may be different for ultra-narrow row (UNR) cotton than for cotton grown in conventional (30 to 40 inch) spacings. We conducted a 3 year field study to determine the potassium need of cotton, as affected by row spacing (8-inch UNR or 36-inch row) and tillage system (chisel plowing or no-tillage). Ultra-narrow row cotton consistently resulted in substantial yield increases compared to conventional row spacing but the potassium need for UNR cotton was similar to that of cotton grown with the conventional row width. Adequate potassium was required to maintain fiber quality, especially with UNR cotton and/or no-tillage cotton. Producers contemplating growing UNR cotton are advised that a sound potassium fertility program is critical to maintain yield levels and fiber quality of cotton grown in this system.

Technical Abstract: Potassium (K) needs for conventional spaced (30 to 40-inch row) cotton (Gossypium hirsutum L.) have been well researched and established, but there has been no published data on K requirements of ultra-narrow row (UNR) cotton. We conducted a replicated 3 year study on a Lucedale sandy loam (Rhodic Paleudults) in central AL to determine the K need of cotton, as impacted by row spacing and tillage system. Treatments were a factorial arrangement of K fertilizer rate (long-term applications of 0, 30, or 60 lb K2O/A), row spacing (8-inch UNR or 36-inch conventional), and tillage system (chisel disk or no-tillage). Cotton lint yields ranged from 142 to 1253 lb/A during the 3 year study, depending on season and treatment combinations. Ultra-narrow row cotton consistently resulted in substantial yield increases compared to conventional row spacing (98% increase, averaged over tillage, K rates and years). Ultra-narrow row cotton yield response to K was similar to that of cotton grown in conventional row widths and UNR spacing with adequate K fertilization (to 60 lb K20/A), consistently provided the highest yield. In two of three years, this row spacing-K fertilizer combination was optimized with no-tillage. Fiber quality, as determined from HVI, varied with year, row spacing, tillage, and K fertilization. Adequate K (60 lb K2O/acre on this soil) was required to maintain micronaire readings, especially with UNR cotton and/or no-tillage cotton. Although it remains to be seen whether UNR cotton will be accepted by the market, our results suggest that adequate K nutrition is critical to optimize yield levels and fiber quality of UNR cotton.