Soil carbon storage potential of direct seeding mulch‐based cropping systems in the Cerrados of Brazil

Abstract

No-tillage cropping systems with direct seeding into a mulch of plant residues from cover crops -the so-called direct seeding mulch-based cropping (DMC) systems -have been adopted widely over the last 10-15 years in the Cerrado region of Brazil. They are replacing the traditional soybean monoculture with bare fallow using conventional tillage (CT) practices. The objective of this study was to examine how DMC practices affect soil organic carbon (SOC) dynamics and to assess their potential for enhanced soil carbon (C) storage. The approach was to determine soil C stocks along a chronosequence of fields under DMC, and then to apply the generic decomposition and yield (G'DAY) plant-soil model to analyse the soil C storage potential for a number of cropping systems. Forty-five fields were selected on a plateau of Ferralsols in the central Cerrado region to represent a chronosequence of 0-12 years under continuous DMC. Before DMC the fields had been under CT soybean monoculture following the clearing of the native savannah. An average increase in SOC stocks of 0.83 Mg C ha À1 yr À1 in the 0-20 cm topsoil was measured. The corresponding increase in total soil nitrogen was 79 kg N ha À1 yr À1 . The G'DAY model predicted a net accumulation of 0.70-1.15 Mg C ha À1 yr À1 in the 0-40 cm topsoil for the first 12 years, depending on the type of soil and DMC system. Model predictions showed that less soil C was accumulated under DMC systems that commenced immediately after clearing the native savannah. Gains in soil C under DMC were primarily due to the introduction of a second crop that caused higher net primary productivity, leading to higher plant C inputs to soil. A rough estimation shows that the conversion of 6 million ha of CT soybean monoculture to DMC in the Cerrados would enhance soil C storage by 4.9 Tg C yr À1 during at least the first 12 years following the conversion to DMC.

Carbono, matéria orgânica leve e fósforo remanescente em diferentes sistemas de manejo do solo

“…Os resultados de estoque de carbono encontrados neste estudo são considerados baixos se comparados com outros trabalhos da literatura (Bayer et al, 2004;Wendling et al, 2005;Corbeels et al, 2006;Blanchart et al, 2007;Siqueira Neto et al, 2009). Entretanto, o acúmulo de C pode variar regionalmente devido às condições climáticas (Carvalho et al, 2010), ao tipo de solo (Bayer & Mielniczuk, 1999), ao manejo aplicado e, principalmente, em função do tempo de implantação do SPD (Carvalho et al, 2009).…”

“…Apesar de na literatura serem encontrados dados sobre os teores e estoques de carbono orgânico, em solos cultivados no Cerrado (Bayer et al, 2004;Wendling et al, 2005;Corbeels et al, 2006;Blanchart et al, 2007;Siqueira Neto et al, 2009), ainda são necessárias mais informações sobre os teores de MOS e os valores de Prem em experimentos de longa duração com uso de plantas de cobertura.…”

Cotton expansion and biodiversity loss in African savannahs, opportunities and challenges for conservation agriculture: a review paper based on two case studies

“…Runoff transports sediments, nutrients and possibly erosion-related pollutants to streams, lakes, estuaries and coral reefs (Farella et al 2001). Moreover, the conversion from a large to a small standing-biomass ecosystem leads to a release of organic carbon to the atmosphere, particularly under tropical conditions (Corbeels et al 2006). This release can be an important contribution to global climate change (Vitousek et al 1997;Corbeels et al 2006).…”

“…Moreover, the conversion from a large to a small standing-biomass ecosystem leads to a release of organic carbon to the atmosphere, particularly under tropical conditions (Corbeels et al 2006). This release can be an important contribution to global climate change (Vitousek et al 1997;Corbeels et al 2006). Thus, agriculture may alter regional and even global hydrological and biogeochemical cycles and affect distant biodiversity.…”

Soil fertility status, carbon and nitrogen stocks under cover crops and tillage regimes

“…Modeling simulations for the Brazilian Cerrado indicated that soil C and N stocks under soybean monoculture with bare fallow declined approximately 20% after 50 years under no-tillage (CORBEELS et al, 2006). A more intensive agriculture combined with NTS practices can enhance C-accumulation rates by increasing biomass production whereby greater amounts of crop residues are returned to the soil (BATLLE-BAYER et al, 2010).…”