Phonolite Rock Powder Promotes Adequate K and Na Nutrition and Cycling in Eucalypt Stands Even During Drought

Phonolite rock powder is an alternative to potassium fertilizer, having applicable K and Na content among rocks, as well as others nutrients (e.g. Ca, S and Si). The study tested the effects of replacing KCl with phonolite rock powder on tree growth, nutrition, and nutrient cycling in a Eucalyptus stand. We compared four top dressing fertilization treatments: PHO (91.7 kg ha− 1 of K and 47.5 kg ha− 1 of Na, applied via phonolite); SOD (54.2 kg ha− 1 Na, applied via NaCl); KCl (91.7 kg ha− 1 of K), and Control (no top dressing fertilization); where KCl and SOD present equivalent molar amount (2.33 kmol). Leaf K concentrations were elevated in the KCl treatment and leaf Na concentrations were elevated in the SOD treatment. Leaf K and Na concentrations in the phonolite rock powder treatment were similar to or lower than those in the KCl and SOD treatments. There were no differences among treatments in tree growth, volume, and aboveground biomass, probably due to a prolonged drought, during which precipitation was 27