Bioethanol from sugarcane is becoming an increasingly important alternative energy source worldwide as it is considered to be both economically and environmentally sustainable. Besides being produced from a tropical perennial grass with high photosynthetic efficiency, sugarcane ethanol is commonly associated with low N fertilizer use because sugarcane from Brazil, the world's largest sugarcane producer, has a low N demand. In recent years, several models have predicted that the use of sugarcane ethanol in replacement to fossil fuel could lead to high greenhouse gas (GHG) emission savings. However, empirical data that can be used to validate model predictions and estimates from indirect methodologies are scarce, especially with regard to emissions associated with different fertilization methods and agricultural management practices commonly used in sugarcane agriculture in Brazil. In this study, we provide in situ data on emissions of three GHG (CO₂, N₂O, and CH₄) from sugarcane soils in Brazil and assess how they vary with fertilization methods and management practices. We measured emissions during the two main phases of the sugarcane crop cycle (plant and ratoon cane), which include different fertilization methods and field conditions. Our results show that N₂O and CO₂ emissions in plant cane varied significantly depending on the fertilization method and that waste products from ethanol production used as organic fertilizers with mineral fertilizer, as it is the common practice in Brazil, increase emission rates significantly. Cumulatively, the highest emissions were observed for ratoon cane treated with vinasse (liquid waste from ethanol production) especially as the amount of crop trash on the soil surface increased. Emissions of CO₂ and N₂O were 6.9 kg ha⁻¹ yr⁻¹ and 7.5 kg ha⁻¹ yr⁻¹, respectively, totaling about 3000 kg in CO₂ equivalent ha⁻¹ yr⁻¹.

While food and nutrition security are issues that national and international organizations are tackling, one of the central problems often overlooked is the essential role of soils in providing nutritious food. Soils are the base for food production and food security. However, the majority of soils are in fair and poor conditions, with the most significant threats being erosion and loss of nutrients. In this study, we estimate the potential of soil loss, agricultural productivity loss, and nutrient loss for Brazil’s most important agricultural region, the Brazilian Cerrado, for the years 2000 and 2012. For this, we applied the Revised Universal Soil Loss Equation (RUSLE) model integrated with a geographical information system (GIS) to estimate annual soil loss rate and agricultural productivity loss, and used total nitrogen and total phosphorus in soil to estimate the annual nutrient loss rate caused by soil loss. All model factors and data were obtained from the literature. The results show that agricultural expansion in the Brazilian Cerrado is increasing the area of severe erosion, occasioning agricultural productivity decrease and soil nutrient depletion. The annual soil loss rate increased from 10.4 (2000) to 12.0 Mg ha⁻¹ yr⁻¹ (2012). Agricultural productivity loss occurred in more than 3 million hectares of crops and silviculture in 2000 and in more than 5.5 million hectares in 2012. Severely eroded areas lost between 13.1 and 25.9 times more nutrients than areas with low and moderate soil loss rates. These findings show that government policy should be directed to ensure the sustainable use of soils, mainly in agriculturally consolidated regions of the Brazilian Cerrado.

We estimated carbon and nitrogen stocks in aboveground biomass (AGB) and belowground biomass (BGB) along an elevation range in forest sites located on the steep slopes of the Serra do Mar on the north coast of the State of São Paulo, southeast Brazil. In elevations of 100 m (lowland), 400 m (submontane), and 1000 m (montane) four 1‐ha plots were established, and above‐ (live and dead) and belowground (live and dead) biomass were determined. Carbon and nitrogen concentrations in each compartment were determined and used to convert biomass into carbon and nitrogen stocks. The carbon aboveground stock (C_AGB) varied along the elevation range from approximately 110 to 150 Mg·ha⁻¹, and nitrogen aboveground stock (N_AGB), varied from approximately 1.0 to 1.9 Mg·ha⁻¹. The carbon belowground stock (C_BGB) and the nitrogen belowground stock (N_BGB) were significantly higher than the AGB and varied along the elevation range from approximately 200–300 Mg·ha⁻¹, and from 14 to 20 Mg·ha⁻¹, respectively. Finally, the total carbon stock (C_TOTAL) varied from approximately 320 to 460 Mg·ha⁻¹, and the nitrogen total stock (N_TOTAL) from approximately 15 to 22 Mg·ha⁻¹. Most of the carbon and nitrogen stocks were found belowground and not aboveground as normally found in lowland tropical forests. The above‐ and belowground stocks, and consequently, the total stocks of carbon and nitrogen increased significantly with elevation. As the soil and air temperature also decreased significantly with elevation, we found a significantly inverse relationship between carbon and nitrogen stocks and temperature. Using this inverse relationship, we made a first approach estimate that an increase of 1°C in soil temperature would decrease the carbon and nitrogen stocks in approximately 17 Mg·ha⁻¹and 1 Mg·ha⁻¹of carbon and nitrogen, respectively.

Soils of tropical forests are important to the global budgets of greenhouse gases. The Brazilian Atlantic Forest is the second largest tropical moist forest area of South America, after the vast Amazonian domain. This study aimed to investigate the emissions of nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) fluxes along an altitudinal transect and the relation between these fluxes and other climatic, edaphic and biological variables (temperature, fine roots, litterfall, and soil moisture). Annual means of N₂O flux were 3.9 (± 0.4), 1.0 (± 0.1), and 0.9 (± 0.2) ng N cm⁻² h⁻¹ at altitudes 100, 400, and 1000 m, respectively. On an annual basis, soils consumed CH₄ at all altitudes with annual means of −1.0 (± 0.2), −1.8 (± 0.3), and −1.6 (± 0.1) mg m⁻² d⁻¹ at 100 m, 400 m and 1000 m, respectively. Estimated mean annual fluxes of CO₂ were 3.5, 3.6, and 3.4 μmol m⁻² s⁻¹ at altitudes 100, 400 and 1000 m, respectively. N₂O fluxes were significantly influenced by soil moisture and temperature. Soil-atmosphere exchange of CH₄ responded to changes in soil moisture. Carbon dioxide emissions were strongly influenced by soil temperature. While the temperature gradient observed at our sites is only an imperfect proxy for climatic warming, our results suggest that an increase in air and soil temperatures may result in increases in decomposition rates and gross inorganic nitrogen fluxes that could support consequent increases in soil N₂O and CO₂ emissions and soil CH₄ consumption.