Effects of organic and inorganic fertilizers on greenhouse gas (GHG) emissions in tropical forestry Danilo Ignacio de Urzedo, Mariana Pires Franco, Leonardo Machado Pitombo, Janaina Braga do Carmo ⇑ Science and Technology Center for Sustainability, Federal University of São Carlos, Sorocaba 18052-780, Brazil article info Article history: Received 16 April 2013 Received in revised form 9 August 2013 Accepted 10 August 2013 Available online 6 September 2013 Keywords: Reforestation Organic waste GHG Emission factor Calophyllum brasiliense abstract The production of organic wastes tends to increase in a manner that is proportional to human population growth. Currently, applying these wastes to soils is being considered as an alternative solution for the over production of organic waste. However, the levels of greenhouse gas (GHG) emissions from organic waste applications in tropical forestry are unknown. The aim of the present study was to quantify soil carbon dioxide (CO 2 ), nitrous oxide (N 2 O) and methane (CH 4 ) emissions from a reforestation project, where trees (Calophyllum brasiliense) were fertilized with different mineral and organic waste materials. A randomized trial was established to measure soil GHG emissions from plots fertilized with sewage sludge compost (SSC), sewage sludge (SS), mineral fertilizer (Min Fert) and a control (C). C. brasiliense seedling spaced in 3 m  2 m intervals were place into a planting hole which had fertilizer incorporated for seedling establishment. Soil GHG were measured using the static chamber method, placing chambers on the surface of the soil and taking measurements over time, during 172 days in a dry season. Organic wastes (SS and SSC treatments) had significantly higher soil CO 2 fluxes than mineral fertilizer and control plots, with soil CO 2 fluxes of 6.35 ± 1.17 and 9.33 ± 0.96 g C m 2 day 1 , respectively. The application of organic wastes promoted a drastic increase in soil N 2 O emissions treated with SSC (141.19 mg ± 21 N m 2 day 1 , p < 0.01), which had a higher emission factor (2.11%). Average soil CH 4 flux on collection days was 0.1 ± 0.2 mg C m 2 day 1 , although cumulative soil CH 4 emissions over the 5 months study period was positive for the SS treatment, demonstrating the potential emission of GHG from this treatment. Apparently, the variation in fluxes between treatments with organic residues was influenced by differences in the physical and chemical compositions of the wastes and the amounts of labile carbon added. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Emissions of greenhouse gases (GHGs) have attracted broad interest because of the various potential consequences of climate change (Lal et al., 1995). Of the several GHGs, carbon dioxide (CO 2 ) is recognized as the largest contributor to the greenhouse ef- fect due to the large amount produced; it represents approximately 60% of total radioactive forcing among the long-lived GHG (Forster et al., 2007). Since 1750, approximately 35% of anthropogenic CO 2 emissions have been directly related to changes in land use (Foley et al., 2005). Despite the fact that methane (CH 4 ) and nitrous oxide (N 2 O) are present at much lower concentrations than that of CO 2 in the atmosphere, these gases potentially cause much more signifi- cant greenhouse effects, 298 times greater for N 2 O and 25 times greater for CH 4 (Forster et al., 2007). The main mode of N 2 O emission from human activities is from agricultural practices (Forster et al., 2007). However, analyzing the contribution of land use to global warming is difficult to quantify because GHGs arise from diffuse sources and complex systems (Foley et al., 2005). Soil management systems are important for carbon (C) sinks and to promote produc- tivity are needed to mitigate global warming (Johnson et al., 2011); the application of mineral fertilizers and organic residues can alter soil GHG emissions, although the response varies in function of sev- eral factors such as changes in temperature, precipitation and waste composition (Scott et al., 2000). The application of sewage sludge onto soil as an organic fertilizer is an alternative solution for a seri- ous problem concerning the final destination of this waste because it is composed largely of nutrients required by plants (Chiba et al., 2008). Sewage sludge and sewage sludge compost provides improvements in the aggregation of particles and in soil structure, promoting root development and water infiltration and, therefore, plant growth (von Sperling and Gonçalves, 2001). Sewage sludge and sewage sludge compost consists mainly of a material that is rich in nitrogen, which leads to productivity gains for crops and reduced consumption of mineral fertilizers (Chiba et al., 2008). Soil management systems that add organic wastes and incorpo- rate carbon have been evaluated as important alternatives for 0378-1127/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2013.08.018 ⇑ Corresponding author. Tel.: +55 15 32295948; fax: +55 15 32296001. E-mail address: jbcarmo2008@gmail.com (J.B. do Carmo). Forest Ecology and Management 310 (2013) 37–44 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco