Foliar Potassium Fertilizer Additives Affect Soybean Response and Weed Control with Glyphosate

Abstract

Research in 2004 and 2005 determined the effects of foliar-applied K-fertilizer sources (0-0-62-0 (%N-%P 2 O 5 -%K 2 O-%S), 0-0-25-17, 3-18-18-0, and 5-0-20-13) and additive rates (2.2, 8.8, and 17.6 kg K ha −1 ) on glyphosate-resistant soybean response and weed control. Field experiments were conducted at Novelty and Portageville with high soil test K and weed populations and at Malden with low soil test K and weed populations. At Novelty, grain yield increased with fertilizer additives at 8.8 kg K ha −1 in a high-yield, weed-free environment in 2004, but fertilizer additives reduced yield up to 470 kg ha −1 in a low-yield year (2005) depending on the K source and rate. At Portageville, K-fertilizer additives increased grain yield from 700 to 1160 kg ha −1 compared to diammonium sulfate, depending on the K source and rate. At Malden, there was no yield response to K sources. Differences in leaf tissue K ( P = 0.03 ) , S ( P = 0.03 ) , B ( P = 0.0001 ) , and Cu ( P = 0.008 ) concentrations among treatments were detected 14 d after treatment at Novelty and Malden. Tank mixtures of K-fertilizer additives with glyphosate may provide an option for foliar K applications.