Impacts of land use and cover changes on soil nitrogen balance in the brazilian cerrado region

• Autor(a) principal: Luciene Gomes
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações do INPE
• Texto Completo: http://urlib.net/sid.inpe.br/mtc-m21b/2017/10.27.17.30

How has agricultural extensification and intensification affected nitrogen cycle in the Brazilian Cerrado? How will it affect nitrogen cycle in the future? Nitrogen is an essential element to food production. Little nitrogen indicates low crop productivity and soil degradation, while too much of it indicates environmental pollution that is detrimental to environmental health, economic prosperity, and food security. First, we conducted a spatial assessment of soil nitrogen balance in the Brazilian Cerrado based on land use dynamics in the years 2000, 2010, and 2012. Second, in order to explore trajectories of agricultural expansion and estimate soil nitrogen balance for the year 2050, we developed a spatially explicit modelling approach capable of representing land use change and soil nitrogen balance for the Cerrado. The trajectories were examined: Sustainability (A); Middle of the road (B); and Fragmentation (C). First results show a movement toward soil nitrogen depletion. In 2000 the balance shows a slight nitrogen accumulation (0.07 TgN) to a condition of nitrogen depletion (-0.37 TgN) in 2012. Such results suggests that agricultural practices in the Cerrado region have been mining soil nitrogen, potentially affecting soil sustainability. Silviculture, annual crops (e.g soybeans and maize), and pasture were found to be the main drivers of nitrogen depletion. Second results show negative soil nitrogen balance in all trajectories: -0.94 TgN (A), -3.19 TgN (B), and -1.69 TgN (C). Only in the sustainability scenario (A), where natural vegetation was maintained and better agricultural production practices were applied, soil nitrogen was less affected. Silviculture and pasture continued to be the main drivers of soil nitrogen depletion in all trajectories. Unless an effective government program of sustainable land management is implemented, areas of inefficient nitrogen management will expand, compromising agricultural production and ecosystems services.