Amendoim forrageiro aumenta a produtividade animal e reduz a emissão de gases de efeito estufa em região de clima tropical

Abstract

Forage grasses mixed with legume is a strategy to increase the sustainability of cultivated pastures with ecological and economic benefits. The study aimed to evaluate animal performance and the balance of greenhouse gas emissions in Nellore heifers in the pasture of Brachiaria brizantha cv. Marandu with or without nitrogen or mixed with Arachis pintoi cv. BRS Mandobi. The experimental design was a randomized complete block with three treatments: (1) mixed Marandu palisadegrass (Brachiaria brizantha) and forage peanut (Arachis pintoi) without N fertilizer (MIXED); (2) Marandu palisadegrass monoculture (N FERTILIZER); (3) monoculture Marandu palisadegrass without N fertilizer (CONTROL), with four, replicates, with repeated measures over time (seasons). The fertilized system showed greater herbage mass (p < 0.047), stocking rate (p < 0.001), and gain/area in kg/ha/year (p < 0.001) followed by the mixed and control systems. Regarding methane emissions, heifers in the mixed treatment had lower methane emissions in g/animal/d (p = 0.001), g/d/kg BW (p = 0.018), and g/d/kg BW0.75 (p = 0.009) compared to the other treatments. The N utilization by fertilizer or biological nitrogen fixation had lower CH4 emission (g/kg DMI) than control system (p = 0.044). Mixed system had lower N2O emissions (kg/animal/day and kg/gain/carcass) than the fertilizer system, however, greater than control system (p < 0.001). Animals in the fertilizer had greater N2O emissions of g/kg gain and kg/ha/year than the other treatments (p < 0.001). The fertilized system had greater N excretion (total, urine, and feces), N2O emissions (total, urine, and feces), and NH3 (total, urine and feces) when measured in g/animal/day and kg/ ha/season when compared with mixed and control systems (p < 0.05). N2O emissions as a function of BW (mg/d/kg BW and mg/d/kg BW0.75) and intake (g/kg DMI and g/kg BW) were greater in fertilized system than the other systems (p < 0.01). Fertilized system had greater NH3 emissions (g/d/kg BW, g/d/kgBW0.75, g/kg CMS, g/kg CMOd, and g/kg CPB) compared to the other treatments (p < 0.001). The mixed system had lower total emissions in Mg CO2eq/ha, kg CO2eq/kg gain, and kg CO2eq/kg carcass than the fertilized system (p < 0.001). The use of nitrogen via biological fixation is a strategy for pasture intensification with mitigating greenhouse gas emissions.