Strategies for potassium fertilization to improve coffee drink quality and fertilizer technologies for efficient use of nitrogen in different corn planting systems

Abstract

The evolution in the productive potential of crops, combined with the favorable climate conditions, contributed to the success of agriculture in Brazil. The use of technologies for fertilizers, aiming to increase the use efficiency of the primary sources, should follow the same path. In this sense, technologies for the efficient use of nutrients can contribute to the proper supply of nutrients to plants and may improve the quality of harvested products. Brazil stands out as the largest coffee producer in the world, and the major challenge of Brazilian coffee production is to achieve increasing yields while improving the quality of the beverage. Potassium (K) is one of the most essential nutrients for the quality of the coffee beverage. Thus, several studies were conducted to monitor the influence of K on the quality of the coffee beverage. Some of these studies indicate that chloride (Cl), the accompanying ion of K in potassium chloride (KCl), can reduce the quality of the coffee beverage, when present in high concentrations. Therefore, other sources than KCl should be investigated, aiming to improve the quality of the harvested grains. Besides coffee, the country stands out in the production of grains under the no-tillage (NT) system. No-tillage promotes multiple benefits to soil health and crop yields. However, one potential drawback of NT systems is the reduced use efficiency of nitrogen (N), the most required nutrient by corn, when urea is used as an N source. Such reduced efficiency is due to the presence of the straw layer, which can enhance urease activity and reduce the contact of the fertilizer with soil. The fertilizer market already has products that can enhance N use efficiency, such as urease inhibitors. Thus, the challenge is to study the behavior of such additives in various cropping systems since the urease activity is higher in NT than in conventional tillage. Thus, the objective of the first chapter of this work was to study the effect of the physical mixture of KCl and potassium sulfate (K2SO4) sources in different proportions and their influence on the nutritional status, yield, chemical composition, and quality of the coffee beverage. As for the second chapter, the aim was to evaluate urease inhibitors in the treatment of urea applied as topdressing under NT and CT systems, and their efficiency in mitigating N-NH3 losses and improving nutrition and yield of corn grown in the second crop season. For the first chapter, it was observed that the stock of Cl reduces the over time; fertilization with KCl reduces the cup quality grade and PPO activity, probably to the negative effect by the ion probably. The increased application of the cloro in top-dressing have of the direct relationship with the increase of potassium leaching and electrical conductivity. The analyses potassium leaching and electrical conductivity, it may show that coffee beans damage due to use of Cl. As for the second chapter, the fertilizers as ammonium nitrate, and ammonium sulfate had the lowest N-NH3 losses, regardless of tillage system. The urea + NBPT reduced the mean N-NH3 loss by 33% compared to prilled urea. The urea + NBPT (1,200 mg kg-1) and urea + NBPT (180 mg kg-1) reduced by 72% and 22% the N-NH3 losses compared to prilled urea in the no-till system.