The objective of this work was to evaluate alternative sources of potassium for improving soil fertility and coffee productivity and beverage quality. The experiment was conducted in a coffee (Coffea arabica) crop, planted in an Oxisol area, in the municipality of Patrocínio, in the state of Minas Gerais, Brazil. The treatments consisted of the K sources TK47 and Super Greensand (SG) - both based on glauconite silicate mineral -, at the following doses: 0 kg ha^-1 K₂O (control); 42, 84, 168, and 336 kg ha^-1 K₂O from TK47; 618 kg ha^-1 K₂O from KCl; and 168 kg ha^-1 K₂O from SG. A randomized complete block design was used, with four replicates in each treatment. The experimental units consisted of three rows with ten plants each, using the eight central plants as the useful plot. Potassium fertilization with TK47 increased soil fertility, correcting soil acidity and elevating K⁺, P, and Ca²⁺ contents, effective cation exchange capacity, and Zn²⁺ and Fe²⁺ levels in the soil. Fertilization with 336 kg ha^-1 K₂O from TK47, in a single dose, provides grain yield and polyphenol oxidase activity similar to those of fertilization with 618 kg ha^-1 K₂O from KCl, in a split-dose, but a better sensory analysis of the resultant beverage.

The aim of the present study was to investigate the effects of magnesium on the gas exchange and photosynthetic efficiency of Coffee seedlings grown in nutrient solution under different light levels. The experiment was conducted under controlled conditions in growth chambers and nutrient solution at the Department of Plant Pathology of the Federal University of Lavras. The treatments consisted of five different Mg concentrations (0, 48, 96, 192 and 384 mg·L⁻¹) and four light levels (80, 160, 240 and 320 µmol photon m⁻²·s⁻¹). Both the Mg concentration and light levels affected gas exchange in the coffee plants. Photosynthesis increased linearly with the increasing light, indicating that the light levels tested were low for this crop. The highest CO₂ assimilation rate, lowest transpiration, and highest water use efficiency were observed with 250 mg·Mg·L⁻¹, indicating that this concentration was the optimal Mg supply for the tested light levels.

Phosphorus (P) is considered one of the nutrients that most limits crop yields, especially in soils with an advanced degree of weathering. To evaluate P dynamics and availability in soil resulting from various P doses and sources and to assess the resulting P content of coffee leaves and the final coffee yield, an experiment was conducted in the municipality of Três Pontas, MG, Brazil, in a Red Argisol (Ultisol) area. Fertilization, except for P fertilization, was performed based on the soil analysis results. The annual P doses tested were 0, 75, 150, 300, 450 and 600 kg ha-1 P2O5. Two P sources, simple superphosphate and magnesium thermal phosphate, were evaluated and compared in the study. A physicochemical analysis of the soil and an analysis of leaf dry matter were performed. The available P content in the soil increased as a result of the applications of the two sources. The leaf P levels stabilized at approximately 1.8 and 1.9 g kg-1 for simple superphosphate and magnesium thermal phosphate, respectively, as a result of the application of approximately 300 kg ha-1 P2O5. The coffee responded to P fertilization in the production phase. Averaged over three harvests, the yield per harvest showed gains of 45.3% and 40.3% for simple superphosphate and magnesium thermal phosphate, respectively, with the application of the highest studied dose, 600 kg ha-1 P2O5.