Influence of Variable Chloride/Sulfur Doses as Part of Potassium Fertilization on Nitrogen Use Efficiency by Coffee
2023
Victor Hugo Ramirez-Builes | Jürgen Küsters | Ellen Thiele | Luis Alfredo Leal-Varon | Jorge Arteta-Vizcaino
Chloride (Cl&minus:) is applied in coffee at rates as a &ldquo:macronutrient&rdquo: in the form of muriate of potash (MOP). Potassium (K+) is one of the most demanded nutrients by the coffee plant, and MOP is one of the most used fertilizers in coffee production. No scientific evidence shows how Cl&minus: applied with MOP influences coffee growth, nutrient uptake, and nitrogen use efficiency (NUE). In order to address these questions, a greenhouse trial over two years and a field trial over four years were conducted. The trials were designed to test the influence of variable Cl&minus:/S ratios on biomass accumulation, nutrient uptake, and NUE. A significant effect of the Cl&minus: rates on growth was observed under greenhouse conditions but a non-significant effect on yield under field conditions. Cl&minus: and S significantly influenced the NUE in coffee. The results allow us to conclude that Cl&minus: rates need to be balanced with S rates, and that Cl&minus: applied at macronutrient rates can improve the NUE in coffee between 7 and 21% in greenhouse conditions and between 9% and 14% in field conditions, as long as the rates do not exceed 180 mg L&minus:1 Cl&minus: and 80 mg·:L&minus:1 S in the greenhouse and 150 kg·:ha&minus:1·:year&minus:1 Cl&minus: and 50 kg ha&minus:1·:year&minus:1 S in the field. With the aim to improve the NUE in coffee, the Cl&minus: content in leaves in coffee should be lower than 0.33% of dry matter, and in soil lower than 30 mg·:L&minus:1. In practical terms, coffee farmers need to balance K-based fertilizers to avoid the excessive Cl&minus: applications that reduce the nutrient use efficiency, especially the NUE.
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