RESUMO

Foliar fertilization with macro and micro minerals for the forage grasses establishment can be a less costly alternative for the farmer, however the possible beneÀ ts of this management technique still need to be better studied. The objective with this work was to evaluate the physiological, productive and structural responses of grasses of the Urochloa genus, depending on the application or not of foliar fertilizer during the plant establishment. Four experiments were carried out, in each of which one of the following forage grasses was evaluated: Urochloa brizantha cv. Marandu, Urochloa spp. Mulatto II, Urochloa spp. Mavuno and Urochloa spp. Ipyporã. All the experiments were carried out from November 2018 to March 2019, in a completely randomized design, with four replications. The experimental area of each experiment consisted of four plots with 12.25 m², where half the area of the plots received foliar fertilizer (FH PASTAGEM FOLIAR, with 14% N; 12% P; 12% K; 0.38 % Mg; 10.2% S; 0.24% Cu; 0.18% Mn and 0.63% Zn) and the other half did not. The response variables were evaluated: spad index, leaf area index, canopy light interception, forage production and root density. In all experiments, the foliar fertilizer application during the establishment of Marandu, Mulato II, Mavuno and Ipyporã grasses did not inÁ uence (P>0,05) the spad and leaf area indexes, forage production and root density.(AU)

Assuntos

RESUMO

Although highly weathered soils cover considerable areas in tropical regions, little is known about exploration by roots in deep soil layers. Intensively managed Eucalyptus plantations are simple forest ecosystems that can provide an insight into the belowground growth strategy of fast-growing tropical trees. Fast exploration of deep soil layers by eucalypt fine roots may contribute to achieving a gross primary production that is among the highest in the world for forests. Soil exploration by fine roots down to a depth of 10 m was studied throughout the complete cycle in Eucalyptus grandis plantations managed in short rotation. Intersects of fine roots, less than 1 mm in diameter, and medium-sized roots, 1-3 mm in diameter, were counted on trench walls in a chronosequence of 1-, 2-, 3.5-, and 6-year-old plantations on a sandy soil, as well as in an adjacent 6-year-old stand growing in a clayey soil. Two soil profiles were studied down to a depth of 10 m in each stand (down to 6 m at ages 1 and 2 years) and 4 soil profiles down to 1.5-3.0 m deep. The root intersects were counted on 224 m(2) of trench walls in 15 pits. Monitoring the soil water content showed that, after clear-cutting, almost all the available water stored down to a depth of 7 m was taken up by tree roots within 1.1 year of planting. The soil space was explored intensively by fine roots down to a depth of 3 m from 1 year after planting, with an increase in anisotropy in the upper layers throughout the rotation. About 60% of fine root intersects were found at a depth of more than 1 m, irrespective of stand age. The root distribution was isotropic in deep soil layers and kriged maps showed fine root clumping. A considerable volume of soil was explored by fine roots in eucalypt plantations on deep tropical soils, which might prevent water and nutrient losses by deep drainage after canopy closure and contribute to maximizing resource uses.