SOLAR RADIATION IN UNDERSTORY OF AGROSYLVOPASTORAL SYSTEM WITH EUCALYPT ON DIFFERENT SPACINGS

Abstract

The solar radiation in understory of eucalypt stands can be the base to decide about the introduction of annual cropping and pastures in agrosylvopastoral systems. This study determined the levels and distribution of the photosynthetic photon flux density, global solar radiation and illuminance in understory of different spacings of agrosylvopastoral with eucalypt. The experiment was established in December 1999, in cerrado area. It was planted clone seedlings of a natural hybrid of Eucalyptus camaldulensis Dehnh with Eucalyptus urophylla S.T. Blake, intercropped with rice in the first year, soybean in the second and Brachiaria brizantha pasture in following years. The experimental design was randomized blocks, with five repetitions. The treatments were installed in split plots, with the primary treatments constituted by ten spacings of eucalypt stand: 3,33 x 2m, 3,33 x 3m, 5 x 2m, 10 x 2m, 10 x 3m, 10 x 4m, (3 x 3)+7m, (3 x 3)+10m, (3 x 4)+10m and (3 x 3)+15m. The secondary treatments were difned as evaluations in rows and in the space between rows, at 27, 38 and 54 months after planting. The solar radiation in eucalypt s understory changes according the spacing. The canopy closure in lowest spacings promote general shading in understory at two years old. In the highest spacings the space distribution of ligth and shade changes along of the year time.