Biomass quantification and characteristics produced under increased atmospheric CO2 simulated conditions in agricultural system

Abstract

Atmospheric CO2 enrichment increases plants growth rate, raising total biomass production with direct interference in fiber, hemicellulose and lignin content, which has implications in ruminants feeding. The overall project objective is to evaluate the effects of the increased biomass production in response to increased atmospheric CO2 concentration in agricultural system. The goals include determining effects of two contrasting atmospheric CO2 concentration (ambient and 200 ppm above) in biomass production and quality of Brachiaria ssp., forage and soil elementary and isotopic levels, gas flow of soil-plant system; as well as identify benefits and propose interventions aiming the forage production sustainability in environment with increased CO2 concentration. The experiment will be conducted in CENA/USP (Piracicaba, SP) and Embrapa Meio Ambiente (Jaguariúna, SP). The Free air carbon dioxide enrichment (FACE) facility has twelve octagonal 10 m diameter rings located in a 7 ha area. Six rings representing the control treatment are kept in untreated conditions (current CO2 atmosphere), and other six rings are treated with pure CO2 to achieve 200 ppm above ambient concentration. Brachiaria brizantha cv. Marandu was seeded in 5,8 m2 plots within each ring and at regular intervals will be harvested at 20 cm height. Forage production, nutritional quality and characteristics shall be determined for each collection interval throughout the experimental period (2 years). Fiber degradability and methane production will be measured by in vitro gas production at 12 months intervals. At the beginning and at the end of the trial period, organic matter in the soil-plant interface will be evaluated. Greenhouse gases fluxes in the soil-plant system will be analyzed at the end of the trial period. The results aim to contribute to the improvement in Brazil's ability to predict the impact of current and future climate change on Brazilian agriculture; increased accuracy in monitoring emissions and retention of greenhouse gases in the Brazilian agriculture, the provision of technologies and products that enable the farmers remain competitive, adapting to new weather patterns, and promote the reduction of Brazilian greenhouse gases emissions from agricultural activities.