Produtividade e disponibilidade de nutrientes influenciadas pela calagem, adubação NPK e intervalos de colheita em erva-mate

Abstract

Mate (Ilex paraguariensis St. Hil.) is a typical plant of South America, and despite its historical political, social, economic and cultural importance very little technical advance has been observed in the last years. The current planting system is mainly based on extrativism by which the exported nutrients are not replenished and continuous decrease in productivity has been observed. Therefore, this study aimed to evaluate the effect of liming, NPK fertilization and harvesting intervals on mate yield and plant nutrient content and on soil fertility. Six trials were laid out in the field in mate plantations in the 2 x 2 m spacing. The liming study was set in three different sites, and lime supplied at rates corresponding to 0; 0,3; 0,6; 0,9 and 1,2 times the liming need to saturate 100% of the base exchange capacity. Because the lime was broadcast on soil surface, only half of each dose was applied. The study of NPK rates was conducted in one of these sites, and consisted of doses of o; 20; 40; 60; 120 and 240 kg ha-1 of N, or P2O5 or K2O. In each case, the harvesting intervals were: 12, 18 or 24 months. In the liming trial, soil pH, and content of Ca, Mg and Al, in the 0-5, 5-10 and 10-20 cm layers, were determined 18 months after treatment application. In the NPK studies, soil was sampled at 0-10; 10-20 and 20-40 cm depths and analyzed for the respective nutrient tested. In the N trial, the labile and total fractions N and C were analyzed. In all trials, mate leaf, small branches and commercial components (leaf + small branches) yield and plant nutrient content were determined. Mate yield was increased from 21 to 27% by lime rates which rose Ca and Mg soil content to levels considered high by mate growers. Liming reduced Al content in the plant. Mate yield increased with N, P and K rates, especially in longer harvesting intervals. Plant recovering is not complete for harvesting interval of 12 month. Harvesting intervals are recommended for higher yield and for more efficient nutrient utilization by the mate plants.