The understanding of plant morphological and physiological responses to shading can contribute to developing sustainable silvopastoral systems (SPS). Our objective was to evaluate the shading effect on herbage accumulation (HA), plant‐part composition, physiology, and canopy structural characteristics of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf]} under intermittent defoliation in a SPS with Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus urophylla S.T. Blake) in Sinop, Mato Grosso, Brazil. The experimental design was a randomized complete block arranged under a strip‐split‐plot, where the plots were allocated to four distances from the Eucalyptus grove (3, 6, 10, and 15‐m) in the SPS, on both faces (north and south), with four replications. The evaluations were done during two summer rainy seasons (RS1 and RS2) and one dry season (DS). The herbage accumulation (HA) in RS1 (4290 kg DM ha–1) was 51% greater than in RS2. The greatest canopy height, light interception, and leaf area index (LAI) values were measured during RS1 (25 cm, 91%, and 3.5 cm2 cm–2, respectively). Leaf photosynthesis rate was less at the 3‐m distance (12.5 μmol CO2 m–2 s–1) than at other distances (17.3 μmol CO2 m–2 s–1). We conclude that Marandu palisadegrass has the ability to physiologically adapt to shaded environments, although the dynamics along the whole tree growing cycle needs to be considered so that grass productivity can be sustained in the long‐term. Core Ideas Longer shading impacted canopy structure and forage accumulation at 3‐m distance. Physiological responses shows reduced light effects on the forage growth pattern. Morphologic composition and sward characteristics were only affected at 3‐m distance. Leaf photosynthesis rate was lesser close to the grove. Silvopastoral systems is an option for livestock production in the Brazilian Amazon.

Forage accumulation (FA) is a key response in grazing experiments, and estimates of FA in continuously stocked pastures are often obtained using exclosure cages. This study evaluated how 14-, 21-, and 28-d exclusion periods using cages affected morphological, physiological, and morphogenetic responses of continuously stocked 'Mulato II' hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) pastures maintained at 20-and 30-cm canopy height and how this affected estimates of FA. Grazing exclusion resulted in greater rates of leaf elongation (LER; 1.62 vs. 1.37 cm tiller −1 d −1), stem elongation (SER; 0.16 vs. 0.07 cm tiller −1 d −1), leaf growth (101 vs. 86 kg dry matter [DM] ha −1 d −1), and stem growth (3.4 vs. 1.8 kg DM ha −1 d −1) inside the cages compared with outside. Greater LER resulted in greater final leaf length and leaf area index (LAI) in longer exclusion periods. With greater LAI, photosynthesis was greater within the exclosure cages than on pasture (54.5 vs. 43.9 μmol CO 2 m −2 s −1). Greater leaf growth rate, together with same tiller population density and leaf senescence rate (LSR) across exclusion periods, resulted in overestimated FA by 14, 26, and 24% for 14-, 21-, and 28-d exclusions, respectively. There was no effect of canopy height on FA, because greater LER and SER values in 30-cm canopies were compensated by greater LSR. Choice of sites for cage placement by visual appraisal and reduced number of sampling sites resulted on "negative" values of calculated FA for the 14-d exclusion, making the choice of sampling sites a major source of error in estimation of actual FA. Increasing the number of sampling sites and using indirect measurements of forage mass (FM) may increase the accuracy of FM and FA estimates.

Rotational stocking (RS) is generally associated with the intensification of pasture‐based animal production systems, although many studies have shown little advantage over continuous stocking (CS). The objective of this research was to describe and explain the effects of two average canopy heights (20 and 30 cm) and three stocking methods (CS; rotational stocking with lenient defoliation, RSL; and rotational stocking with moderate defoliation, RSM) on forage accumulation (FA), vertical distribution of plant‐part components, and nutritive value of ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) during two summer rainy seasons in Piracicaba, São Paulo, Brazil. Pastures were maintained at average canopy height of 20 and 30 cm under CS, and treatments under RSL and RSM were imposed by variations of ±20 and 30% of the average canopy heights, representing defoliation intensities of 33 and 47% of the pre‐graze heights, respectively. The FA was not affected by CS, RSL, RSM stocking methods, averaging 8090 kg DM ha−1 year−1. Canopy bulk density and distribution of plant‐part components in the canopy profile were better at the average canopy height of 20 cm, accompanied by the greater nutritive value. The leaf bulk density was generally greater in RSM compared to CS. Pastures under CS had greater crude protein and in vitro digestible matter, and lesser neutral detergent fibre concentrations. Mulato II brachiariagrass should be managed at an average height of 20 cm under CS.

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