Potassium fertilization of cotton on two high testing soils under two tillage systems

Abstract

Potassium (K) fertilization of cotton (Gossypium hirsutum L.) has been a major research focus the last few years throughout the cotton belt. The objective of this field research, conducted from 1991 through 1994 on two high Mehlich I extractable K (EK) soils, was to evaluate broadcast and foliar applied K for conventional‐ (CT) and no‐tillage (NT) production. Main plot broadcast K rates were 0, 28, 56, and 112 kg K ha^‐1. Foliar sub‐plot treatments were a non‐foliar check, KNO₃, and Ca(NO₃)₂. The KNO₃ was applied four times per year at 4.1 kg K ha^‐1 application^‐1. Calcium nitrate was applied at 1.6 kg N ha^‐1 to equal the N applied in the KNO₃. Extractable K increased annually with broadcast K for both tillage systems and soils and was higher for NT than CT. Lint yields from CT of both soils were increased two of the eight site‐years while yields from NT were increased five of eight site‐years by broadcast K. Three of the NT site‐year yields plus four‐year mean yields of both soils were increased by applying 56 kg K ha^‐1, a rate higher than currently recommended for high EK soils. Yield responses to foliar fertilization were from added N rather than the K. Petiole K levels were sufficient so that extra K applied foliarly was not recommended for either soil or tillage system.