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 (CO 2 , N 2 O, and CH 4 ) 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 N 2 O and CO 2 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 CO 2 and N 2 O were 6.9 kg ha À1 yr À1 and 7.5 kg ha À1 yr À1, respectively, totaling about 3000 kg in CO 2 equivalent ha À1 yr À1 .

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The environmental benefits of producing biofuels from sugarcane have been questioned due to greenhouse gas emissions during the biomass production stage, especially nitrous oxide (N 2 O) associated with nitrogen (N) fertilization. The objective of this work was to evaluate the use of nitrification inhibitors (NIs) dicyandiamide (DCD) and 3,4 dimethylpyrazole phosphate (DMPP) and a controlled-release fertilizer (CRF) to reduce N 2 O emissions from urea, applied at a rate of 120 kg ha -1 of N. Two field experiments in ratoon cycle sugarcane were performed in Brazil. The treatments were (i) no N (control), (ii) urea, (iii) urea+DCD, (iv) urea+DMPP, and (v) CRF. Measurements of N 2 O fluxes were performed using static chambers with four replications. The measurements were conducted three times per week during the first 3 mo and biweekly afterward for a total of 217 and 382 d in the first and second seasons, respectively. The cumulative N 2 O-N emissions in the first ratoon cycle were 1098 g ha -1 in the control treatment and 1924 g ha -1 with urea (0.7% of the total N applied). Addition of NIs to urea reduced N 2 O emissions by more than 90%, which did not differ from those of the plots without N. The CRF treatment showed N 2 O emissions no different from those of urea. The results were similar in the second ratoon: the treatment with urea showed N 2 O emissions of 0.75% of N applied N. Application of NIs resulted in a strong reduction in N 2 O emissions, but CRF increased emissions compared with urea. We therefore conclude that both NIs can be options for mitigation of greenhouse gas emission in sugarcane used for bioenergy.

were assessed, as well as the tiller contribution to these characters. In 2007/2008, there was no water deficit, LAI values were higher than 7, and tillers contributed with 65% of total LAI at the lowest plant density. In this year, grain yield average (13.7 Mg ha -1 ) was not affected by treatments, and tillers contributed with 44% of total yield at the density of three plants per square meter. In 2008/2009, there was water deficit before flowering and during grain filling, which decreased tillering and tiller contribution to LAI. Grain yield in this year increased from 9.7 to 11.7 Mg ha -1 with increasing plant densities, but tiller contribution to grain yield was lower. Tillering increases phenotypic stability of grain productivity to variations in plant spatial arrangement.

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