Brasil
Brasil
Forage grass canopies may be affected by the shaded microclimate in silvopastoral (SP) systems throughout the year. This in turn may affect forage plant characteristics. Our objective was to assess microclimate effects on the responses of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf.]} under continuous stocking in an SP system with Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus urophylla S. T. Blake). Trees were planted in triple rows (grove), with three groves per 2-ha silvopasture experimental unit (11° 51′ S, 55° 35′ W). The spacing between groves was 30 m, and tree density was 135 ha–1, in East-West orientation. Microclimate and forage plant variables were evaluated from December 2016 to March 2018 in the treatments consisting of “full sun” (FS) grass monoculture pasture and at three distances from the grove: 7.5 m North (7.5 N), 15 m (15), and 7.5 m South (7.5S). Photosynthetically active radiation (PAR) was greatly affected and positively associated with most of the responses of Marandu palisadegrass. On average, PAR reduction in relation to FS was 8, 24, and 40 % for 15, 7.5 N, and 7.5S, respectively. The greatest maximum temperatures (35.8 °C) and the least minimum temperatures (15.8 °C) were registered during the Winter. Both forage accumulation rate (∼ 45 kg ha−1 d-1) and leaf accumulation rate (∼ 19 kg ha-1 d-1) were similar between FS and 7.5S (most shaded distance). Shade tolerance mechanisms of palisadegrass under grazing were associated with increases in specific leaf area and leaf proportion, allowing shaded pastures to sustain productivity at levels equivalent to those of pastures without shade.
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