Profit‐maximizing potassium fertilizer recommendations for corn and cotton. (16th November 2022)

• Record Type: Journal Article
• Authors: Oliver, Kimberly; Popp, Michael P.; Slaton, Nathan A.; Drescher, Gerson Laerson; Roberts, Trenton L.
• Is Part Of: Agronomy Journal. Volume 114:Number 6(2022)
• Page Start: 3358
• Page End: 3376
• Publication Date: 2022-11-16
• Subjects: Agronomy -- Periodicals; 630
• DOI: 10.1002/agj2.21205
• Languages: English
• ISSNs: 0002-1962

Abstract

Abstract: Whereas K fertilization is necessary to maximize corn ( Zea mays L.) and cotton ( Gossypium hirsutum L.) yields in soils with sub‐optimum K availability, maximizing yield is rarely profit‐maximizing. Estimating the tradeoff between yield and fertilizer cost using current soil‐building and/or yield‐maximizing rate recommendations vs. profit‐maximizing fertilizer‐K rates (KR * ) provides insights for producers. Thirty‐nine and 24 fertilizer‐K rate trials were used to estimate respective corn and cotton yield response based on soil‐K availability (SK). Using a field's SK, yield potential, yield response to fertilizer‐K, crop price, and fertilizer‐K cost, KR * were calculated over the past 10 yr. Averaging over that period, using KR * at SK of 75 and 60 mg K kg –1 (a) reduced fertilizer‐K rate by 10 and 38 kg K ha –1, respectively, (b) decreased yield by 53 and 32 kg ha –1, respectively, and (c) increased profitability by US$1.75 and $34.24 ha –1, respectively, in comparison to current recommendations for corn. At SK of 75 and 110 mg K kg –1, cotton profitability at KR * vs. current recommendations rose by $11.54 to $25.95 ha –1, respectively, using 36 and 101 kg K ha –1 more fertilizer, respectively, which led to 27 and 73 kg ha –1 greater yield, respectively. As with prior studies for rice ( Oryza sativa L.) and soybean [ Glycine max (L.) Merr.], corn results suggest using less fertilizer than currently recommended, whereas for cotton, strong yield response to fertilizer‐K and relatively high crop price justified KR * that were above currently recommended rates. A spreadsheet‐based decision tool is online to offer this insight to producers and crop consultants. Core Ideas: Fertilizer‐K rate recommendations often rely on yield response and soil‐test values alone. Adding crop price and K‐fertilization cost may improve the profitability of growing corn and cotton. Fertilizer‐K rates could be profitably reduced for corn producers in the U.S. mid‐South. Fertilizer‐K rates for cotton producers could be profitably raised in the U.S. mid‐South. Online decision support software may aid producers to make complex soil fertility decisions.