Shading effects on canopy and tillering characteristics of continuously stocked palisadegrass in a silvopastoral system in the Amazon biome

摘要

In silvopastoral (SP) systems, forage responses depend on the microenvironment in which the plants develop. Our objective was to evaluate canopy and tillering characteristics of shaded 'Marandu' palisadegrass [Brachiaria brizantha (Hochst A Rich) Stapf, syn. Urochloa brizantha] under continuous stocking in a SP system. Treatments were one full sun (FS) and three shaded systems (silvopasture, SP) corresponding to distances from tree groves: 7.5 m north (SP1), and 15 m (SP2) and 7.5 m south (SP3) studied during two rainy seasons (Year 1 and Year 2). The tree in the SP system was Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden x Eucalyptus urophylla S. T. Blake). The photosynthetic active radiation was greater in FS (923 mu mol m(-2) s(-1)), followed by SP2 (811 mu mol m(-2) s(-1)), SP1 (727 mu mol m(-2) s(-1)) and SP3 (673 mu mol m(-2) s(-1)). Forage accumulation in FS was 15% greater than the mean of SP1, SP2 and SP3 (10,663 kg DM/ha). There was no difference in net accumulation of leaf, stem and dead material, averaging 3,302, 3,420 and 4,063 kg DM/ha respectively. Leaf accumulation and accumulation rate were greater in Year 2, and leaf accumulation rate was similar among treatments (19 kg DM ha(-1) day(-1)). Leaf proportion increased 14% from Year 1 to Year 2. Specific leaf area was greater for treatments SP1 and SP3 (193 cm(2)/g). Tiller population density was similar across treatments in Year 1. Shaded palisadegrass maintains leaf productivity similar to FS under continuous stocking in an SP system.