Pasture characterization and animal performance on silvopastoral systems using tree legumes or grass monoculture

Abstract

The world population is expected to grow by 2050 and also demand for food will increase, it is necessary to find alternatives for a sustainable livestock production. Silvopastoral systems-SPS with tree legumes are promising choices to adapt Agriculture to climate change and provide welfare for cattle, also increase forage nutritive value when the management is applied correctly. This 2-yr study evaluated animal performance and herbage responses in C4-grass monoculture or in SPS in the sub-humid tropical region of Brazil and evaluate productivity and nutritive value of signalgrass [Urochloa decumbens (Stapf.) R. Webster] subjected to shading from the tree legumes gliricidia [Gliricidia sepium (Jacq.) Steud] or mimosa (Mimosa caesalpiniifolia Benth.) under different tree canopy management (harvesting or not one of the rows in the double-row tree planting). The experimental design was randomized complete block with three replications. Treatments were: Urochloa decumbens (Stapf.) R. Webster (Signalgrass) + Mimosa caesalpiniifolia Benth (SPS-Mimosa); Signalgrass + Gliricidia sepium (Jacq.) Kunth ex Walp (SPS-Gliricidia); and Signalgrass monoculture (SM). Response variables included herbage and livestock responses. Cattle were managed under continuous stocking with variable stocking rate. There was interaction between treatment × month for herbage mass. Green herbage accumulation rate ranged from 20 to 80 kg DM ha- 1d-1 across months, with SPS-Mimosa presenting lower rates. Average daily gain was greater in SPS-Gliricidia, followed by SM, and SPS-Mimosa, respectively (0.77; 0.56; 0.23 kg d-1), varying across months. Stocking rate ranged from 0.86 to 1.6 AU ha-1. Total gain per area during the experimental period was greater for SPS-Gliricidia (423 kg BW ha-1), followed by signalgrass in monoculture (347 kg BW ha-1), and SPS-Mimosa (50 kg BW ha-1). The responses variables for different management included canopy height, herbage mass (green leaf blade, green stem, senescent leaves, and senescent stem), herbage accumulation rate, canopy bulk density, and soil moisture, bare soil and botanical composition. Total herbage mass, green herbage mass, and green leaf mass were affected by treatment × evaluation date and harvest management × evaluation date interactions. Herbage accumulation rate in SPS-Gliricidia was greater (55 kg DM ha-1d-1) than SPS-Mimosa (32 kg DM ha-1d-1). Soil moisture was lower at the Mimosa sites (16.2%) compared with the Gliricidia ones (17.2%), and it was greater between tree rows (21.9%) compared with full sun (11.5%), varying across the season. There were significant differences between harvest management for bare soil and litter percentage (P≤0.05). The botanical composition found 36 weed species, distributed in 19 botanical families and 36 of these species were dicotyledonous (53%) and 17 were monocotyledonous (47%). The silvopastoral systems have benefits for the environment, such as the increase of the carbon stock in the biomass and provide more comfort to the animal raised on pasture.