PERFORMANCE EVALUATION OF THE PHONOLITE VIA MINERAL IN ADULT ORANGE TREES
The present study’s goal was to analyze the performance of the Phonolite as a source of potassium in the fertilization management of the orchard of the adult orange trees. The study was conducted under field conditions in a commercial orchard of ‘Pera’ sweet orange trees on 5-year old mandarin lime trees. The randomized block experimental design was used, in a factorial scheme with 3 factors (3 doses of Phonolite (60 kg K2O.ha-1; 120 kg K2O.ha-1; 180 kg K2O.ha-1); 2 doses of Plaster (without Gypsum and with 1 t.ha-1); 2 doses of Limestone (without Limestone and with 1,5 t.ha-1), plus 1 additional treatment with the farmer’s traditional fertilization (120 kg K2O.ha-1 via 20- 00-20), totaling 13 treatments, with 4 repetitions and 5 plants per plot. The treatments were applied on 02/02/2012 with a superficial application by tractor on the soil under the plant canopies, using a Vicon fertilizer spreader, without incorporation. Soil samples were evaluated at 5 depths (0-5, 5-10, 10-15, 15-20 e 20- 40 cm) previously removed, 27, 78 and 118 days after the application, and the fruit production of the plants was evaluated at the end of the crop. However, the fruits that were already on the plants when the Phonolite was applied were harvested. It was concluded that the Phonolite was shown to be as effective as the traditional fertilization to elevate the percentage of potassium in the soil and in the leaf. It also contributed significantly to the increase in the orchard’s productivity.