Carbon balance and crop residue management in dynamic equilibrium under a no-till system in Campos Gerais

Abstract

SUMMARYThe adoption of no-tillage systems (NT) and the maintenance of crop residues on the soil surface result in the long-term increase of carbon (C) in the system, promoting C sequestration and reducing C-CO 2 emissions to the atmosphere. The purpose of this study was to evaluate the C sequestration rate and the minimum amount of crop residues required to maintain the dynamic C equilibrium (dC/ dt = 0) of two soils (Typic Hapludox) with different textural classes. The experiment was arranged in a 2 x 2 x 2 randomized block factorial design. The following factors were analyzed: (a) two soil types: Typic Hapludox (Oxisol) with medium texture (LVTM) and Oxisol with clay texture (LVTA), (b) two sampling layers (0-5 and 5-20 cm), and (c) two sampling periods (P 1 -October 2007; P 2 -September 2008). Samples were collected from fields under a long-term (20 years) NT system with the following crop rotations: wheat/soybean/black oat + vetch/maize (LVTM) and wheat/maize/ black oat + vetch/soybean (LVTA). The annual C sequestration rates were 0.83 and 0.76 Mg ha -1 for LVTM and LVTA, respectively. The estimates of the minimum amount of crop residues required to maintain a dynamic equilibrium (dC/dt = 0) were 7.13 and 6.53 Mg ha -1 year -1 for LVTM and LVTA, respectively. The C conversion rate in both studied soils was lower than that reported in other studies in the region, resulting in a greater amount of crop residues left on the soil surface.Index terms: C sequestration rate, soil texture, subtropical soils.(1) Received for publication in July 25, 2011 and approved in July 10, 2012.(2) Posgraduate student (PhD)

Carbon Depletion by Plowing and its Restoration by No‐Till Cropping Systems in Oxisols of Subtropical and Tropical Agro‐Ecoregions in Brazil

“…Recently, Ferreira et al . () reported that for this region, the minimum amount of biomass‐C input to maintain the steady state was 3·21 Mg ha −1 y −1 , and in this study, the biomass‐C input was 4·15 Mg ha −1 y −1 . The percentage of biomass‐C converted into SOC in this study was 14·2 and was very similar with the findings obtained by Ferreira et al .…”

“…The main reason was the low amount of biomass-C added through residues of summer crop and winter species during the 29 years of experiment and the near absence of legumes as a winter cover crop (Table II). Recently, Ferreira et al (2012) reported that for this region, the minimum amount of biomass-C input to maintain the steady state was 3Á21 Mg ha À1 y À1 , and in this study, the biomass-C input was 4Á15 Mg ha À1 y À1 . The percentage of biomass-C converted into SOC in this study was 14Á2 and was very similar with the findings obtained by Ferreira et al (2012), which was~12Á63-14Á26%.…”

“…Recently, Ferreira et al (2012) reported that for this region, the minimum amount of biomass-C input to maintain the steady state was 3Á21 Mg ha À1 y À1 , and in this study, the biomass-C input was 4Á15 Mg ha À1 y À1 . The percentage of biomass-C converted into SOC in this study was 14Á2 and was very similar with the findings obtained by Ferreira et al (2012), which was~12Á63-14Á26%. There were no significant differences among tillage treatments even with a trend of soils under CT and NT containing relatively more SOC than that under MT in the 40-to 100-cm depth.…”

“…The percentage of biomass‐C converted into SOC in this study was 14·2 and was very similar with the findings obtained by Ferreira et al . (), which was ~12·63–14·26%. There were no significant differences among tillage treatments even with a trend of soils under CT and NT containing relatively more SOC than that under MT in the 40‐ to 100‐cm depth.…”

Chemical and physical fractions of soil organic matter under various management regimes in Roraima, Brazil

“…However, it is crucial to identify the different fractions, as well as the forms of protection under natural vegetation and various agro-management systems (FIGUEIREDO et al, 2010).…”