Implications of Sugarcane Straw Removal for Soil Greenhouse Gas Emissions in São Paulo State, Brazil

Abstract

The use of sugarcane straw is a promising option to enhance bioenergy production. But the implications of straw removal for soil greenhouse gas (GHG) emission are not yet fully understood due to scarcity of studies under Brazilian conditions. Four field experiments were designed to assess soil N 2 O and CH 4 emissions derived from nitrogen (N) fertilization under scenarios of sugarcane straw removal in São Paulo state, Brazil. Our focus was also to derive the direct N 2 O emission factor (EF) that represents the regional conditions of sugarcane production, taking into account the data obtained from this study and those from the literature. In each field study, four straw removal rates (no removal (NR); low removal (LR)-removal of 5 Mg ha −1 ; high removal (HR)-removal of 10 Mg ha −1 ; and total removal (TR)-removal of 15 Mg ha −1) were arranged in a randomized block design. This study shows a clear evidence that CH 4 fluxes are very low for all assessed sites regardless of straw removal rates, indicating a predominance of CH 4 consumption by the soil. Cumulative N 2 O emissions ranged from 0.20 to 4.09 kg ha −1 year −1 and were significantly affected by straw removal in two sites, indicating that straw removal reduces N 2 O emissions. The average direct N 2 O EFs obtained from this study and from the literature were 0.28, 0.44, 0.70, and 0.56% for TR, HR, LR, and NR treatments, respectively, which are consistently lower than the EF of 1% suggested by the IPCC. Based on our regional-specific EF (Tier 2), the direct N 2 O emissions derived from N fertilization under scenarios of straw removal showed a reduction of at least 50% in relation to IPCC approach. Our findings are a step forward in providing regional-specific data to reduce the high level of uncertainty concerning N 2 O emission assessments of sugarcane ethanol in Brazil, but further studies are needed to evaluate how straw removal for bioenergy production and the associated changes in soil organic carbon stocks affect the GHG balance of sugarcane. Keywords Saccharum spp.. CH 4 emissions. N 2 O emissions. N 2 O emission factor. IPCC methodology. Tier 2. Crop residues

Legacy Effects of Intercropping and Nitrogen Fertilization on Soil N Cycling, Nitrous Oxide Emissions, and the Soil Microbial Community in Tropical Maize Production

“…Using a synthetic and sugarcane straw compared to bare soil, Fracetto et al (61) observed that the soil cover was responsible for retaining soil moisture and consequently increasing N 2 O emission regardless of labile C inputs and N mineralization during straw decomposition. The residues left on the field by the forage reduced evaporation an explain the higher soil moisture for soil sampled at 49 DAT (61,62).…”

“…The amount of residue left in the field has been shown to be an important factor controlling soil moisture and consequently N 2 O emission in tropical soils (61,62). Thus, the biomass production by forage grasses may be the main factor driving higher soil moisture, recycling N, and adding labile C consequently increasing N 2 O emission during the maize growing season.…”

Modelling the potential for soil carbon sequestration using biochar from sugarcane residues in Brazil

“…We evaluate the model against published data and use it to make predictions for São Paulo State in Brazil using available data on sugarcane production and relevant soil and climate conditions. São Paulo is a suitable case study because Brazil accounts for 40% of global sugarcane production and São Paulo accounts for 55% of the national production 22 with 96% of its sugarcane fields now mechanically harvested 22,23 . We compare three scenarios in which either 100%, 50% or 25% of the available sugarcane residues are used to produce biochar, with the remaining residues added to the fields as fresh material.…”

Greenhouse gas emissions and offset potential from sugarcane straw for bioenergy production in Brazil

“…The amount of straw deposited on the soil surface after sugarcane green mechanized harvesting, as well as straw management, was determined by collecting samples using a metallic frame of 0.64 m 2 (0.8 m × 0.8 m) in each of the three treatments (5 replications). The samples were oven dried for 24 h at 105 °C until reaching constant weight and then weighed [22] , which resulted in: 25.8 Mg Dry Matter (DM) ha -1 after oven dried for T1; 44.3 Mg DM ha -1 for T2 and 18.9 Mg DM ha -1 for T3. The average amount of straw removed from the field after straw management and recovery operation was calculated as the difference of straw mulch dry matter left on the soil surface between T1 and T3 (T3-T1), which resulted in 6.9 Mg DM ha -1 or 27% of the total straw in the control area.…”