Soil and crop residue CO2-C emission under tillage systems in sugarcane-producing areas of southern Brazil

Abstract

Appropriate management of agricultural crop residues could result in increases on soil organic carbon (SOC) and help to mitigate gas effect. To distinguish the contributions of SOC and sugarcane (Saccharum spp.) residues to the short-term CO 2 -C loss, we studied the infl uence of several tillage systems: heavy offset disk harrow (HO), chisel plow (CP), rotary tiller (RT), and sugarcane mill tiller (SM) in 2008, and CP, RT, SM, moldboard (MP), and subsoiler (SUB) in 2009, with and without sugarcane residues relative to no-till (NT) in the sugarcane producing region of Brazil. Soil CO 2 -C emissions were measured daily for two weeks after tillage using portable soil respiration systems. Daily CO 2 -C emissions declined after tillage regardless of tillage system. In 2008, total CO 2 -C from SOC and/or residue decomposition was greater for RT and lowest for CP. In 2009, emission was greatest for MP and CP with residues, and smallest for NT. SOC and residue contributed 47 % and 41 %, respectively, to total CO 2 -C emissions. Regarding the estimated emissions from sugarcane residue and SOC decomposition within the measurement period, CO 2 -C factor was similar to sugarcane residue and soil organic carbon decomposition, depending on the tillage system applied. Our approach may defi ne new emission factors that are associated to tillage operations on bare or sugarcane-residue-covered soils to estimate the total carbon loss.Keywords: soil respiration, carbon dioxide, emission after tillage, soil organic carbon IntroductionLosses of soil organic carbon (SOC) due to soil management in agricultural areas have been identifi ed as a factor that accelerates the greenhouse effect, especially by emitting CO 2 in the atmosphere (Eugster et al., 2010). Losses of SOC can be assessed either by directly measuring changes in SOC content or by monitoring soil CO 2 emissions. The latter has the advantage to detect immediate or near-immediate effects of management practices on C loss via emissions. The impact of tillage on the loss of SOC and associated emission factors under different management systems has been studied (Smith et al., 2010;La Scala et al., 2008; La Scala et al., 2009 a,b), and some researchers have used tillage emission factors as bias for estimating soil conversion from conventional to no-till. However, Smith et al. (2010) noted that this conversion can be affected by the depth of tillage, and multiple factors should be developed to reduce estimation errors.Agricultural activities contribute with approximately 20 % to the global greenhouse gas emissions (Lokupitiya and Paustian, 2006). No-till farming combined with the maintenance of crop residues on the soil surface has been identifi ed as an important strategy for sequestering carbon (C) from the atmosphere (Lal, 2007). Tillage induces the loss of C as CO 2 by breaking up soil aggregates and exposing the protected organic matter to microbes. Tillage also incorporates and mixes residues, improving aeration, which can lead to additional C losses by maximizin...

Soil respiration after tillage under different fertiliser treatments – implications for modelling and balancing

“…We suppose that the collar of this repetition was placed inadvertently over an accumulation of plant residues buried in the soil. It has been described for other sites that the incorporation of residues increases tillage-induced SR (Alvarez et al, 2001;Dao, 1998;Teixeira et al, 2013). Also in this treatment, precipitation triggered the highest SR of the entire experiment on day 9 since wetting of previously dry soil increases microbial activity and therefore SR in general Kim et al, 2012;Reichstein et al, 2003).…”

Soil tillage and cover crop on soil CO2 emissions from sugarcane fields

“…We believe that the variation in CO 2 emissions during the first 50 DAT was stimulated by cover cropping and tillage and were increased by rainfall events. Several studies indicate that soil tillage increases the oxidation of organic C by releasing large amounts of CO 2 into the atmosphere over a short period of time (Figueiredo, Panosso, Donald, Reicosky, & La Scala, ; Silva‐Olaya, Cerri, La Scala, Dias, & Cerri, ; Teixeira et al., ). At the same time, precipitation events tend to cause changes in soil water content which stimulates microbial activity in addition to infiltration of rainwater causing the expulsion or displacement of air (CO 2 ) from soil porosity, subsequently combining to increase CO 2 emissions (Figueiredo et al., ; Smart & Peñuelas, ).…”

Agronomic and environmental implications of sugarcane straw removal: a major review

“…Soil tillage practices increase the surface contact between soil and straw (also decrease the size of particles). This, combined with higher aeration and temperature, increases microbial activity (La Scala et al ., ; Silva‐Olaya et al ., ; Teixeira et al ., ).…”

“…Teixeira et al . () observed that the association between straw mulching and tillage operations increased CO 2 emissions by 36% when compared to similar tillage practices without straw mulching. Soil tillage practices increase the surface contact between soil and straw (also decrease the size of particles).…”

“…In Brazil, short‐term studies have demonstrated that the removal of sugarcane straw increases soil CO 2 emissions (Corradi et al ., ; Teixeira et al ., ; De Figueiredo et al ., ). Such emissions respond to exponential increases in soil temperature (Davidson et al ., ), which in turn have a remarkable effect on the microbial activity that induces the decomposition of SOM and roots (Silva‐Olaya et al ., ).…”