Carbon cycle of native pasture-based beef cattle production systems in the Pantanal area of the Paraguayan Chaco

Abstract

The objective of the present study was evaluate the carbon cycle in Paraguayan Pantanal area native grassland ecosystems by measuring pasture growth and simulating animal grazing. For this purpose, soil analyzes, annual productivity and forage quality were carried out in 4 agro ecological sites of a 20,000 ha located in Alto Paraguay Department (21º 1' 29.85”S and 58º 17' 38.55” W), from Dec 21, 2019 to Feb 12, 2020. In the selected location was installed an 8 m x 8 m exclusion cage with three treatments (4 m2 subplots), corresponding to cutting intervals (35, 70 and 105 CI days, respectively). The seasonal dry matter (DM) production and the pasture growth rate, adjusted stocking rate at three production levels (50, 70 and 75% breeding rate, respectively), carbon contained in organic matter (OM), root system and aerial biomass accumulated in ground were evaluated. The data were compared using Tukey test with a 5% probability. The emission of greenhouse gases (GG) per head and per ha was simulated and adjusted to breeding livestock to a total area of 6,600 ha and 5,000 grassland ha. The 35 days CI presented 32% higher productivity than 105 days CI in carbon sequestration. The best capture/emission balance per ha was observed in 35 days CI with the 50% breeding rate, producing 1,481 kg of CO2-e ha-1, intensifying and increasing the breeding rate to 75%, the balance decreases to 1,294 kg of CO2-e ha-1. In all cases, livestock in grassland has presented a positive balance when accounting for GG per unit area.