Short-term CO2-C emissions from soil prior to sugarcane (Saccharum spp.) replanting in southern Brazil

Abstract

New management strategies should be identified to increase the potential of bioenergy crops to minimize climate change. This study quantified the impact of sugarcane (Saccharum spp.) harvest systems, straw and soil management on carbon dioxide (CO2) fluxes prior to crop replanting carried out on February 2010 in southern Brazil. The soil studied was classified as Haplustult (USDA Soil Taxonomy). Three sugarcane harvest systems were considered: burned (BH) and green harvest with straw maintained on (GH SM) or removed from (GH SR) the soil surface. Our hypothesis is that intensive tillage and the management of sugarcane crop straw could lead to higher CO2 emissions from soil. We measured CO2 emissions in no-till (NT) conditions and after conventional tillage (CT), and with or without dolomite and agricultural gypsum applications. Soil CO2 emissions were measured with a Li Cor chamber (Model Li-8100). Water content of soil and soil temperature readings were first taken 24 h after tillage, over the next 25 days after tillage with 18 measurement days. The removal of sugarcane straw from the soil surface resulted in the rapid reduction of water content of soil (6% in volume) followed by a 64% increase in soil CO2-C emissions, supporting our hypothesis. Additional soil CO2-C emissions caused by removal of crop straw were 253 kg CO2-C ha(-1), which is as high as CO2-C losses induced by tillage. Dolomite and agricultural gypsum applications did not always increase CO2 emissions, especially when applied on soil surface with crop straw and tilled. The conversion from burned to green harvest systems can improve the soil C sequestration rate in sugarcane crops when combined with reduced tillage and straw maintenance on soil surface. The effect of straw removal and related CO2 emission for electricity generation should be considered in further studies from sugarcane areas.