Soil organic matter, biota and aggregation in temperate and tropical soils - Effects of no-tillage

Abstract

-The long-term stabilization of soil organic matter (SOM) in tropical and temperate regions is mediated by soil biota (e.g. fungi, bacteria, roots and earthworms), soil structure (e.g. aggregation) and their interactions. On average, soil C turnover was twice as fast in tropical compared with temperate regions, but no major differences were observed in SOM quality between the two regions. Probably due to the soil mineralogy dominated by 1:1 clay minerals and oxides in tropical regions, we found a higher aggregate stability, but a lower correlation between C contents and aggregate stability in tropical soils. In addition, a smaller amount of C associated with clay and silt particles was observed in tropical versus temperate soils. In both tropical and temperate soils, a general increase in C levels (≈ 325 ± 113 kg C·ha -1 ·yr -1 ) was observed under no-tillage compared with conventional tillage. On average, in temperate soils under no-tillage, compared with conventional tillage, CH 4 uptake (≈ 0.42 ± 0.10 kg C-CH 4 ·ha -1 ·yr -1 ) increased and N 2 O emissions increased (≈ 1.95 ± 0.45 kg N-N 2 O·ha -1 ·yr -1 ). These increased N 2 O emissions lead to a negative global warming potential when expressed on a CO 2 equivalent basis. La stabilisation à long terme de la matière organique du sol (MOS) dans les régions tempérées et intertropicales est sous la dépendance de l'activité biologique (champignons, bactéries, macrofaune et racines), de la structure du sol (agrégation) et de leurs interactions. En moyenne, si le turnover du carbone du sol (C) est environ deux fois plus rapide en régions intertropicales qu'en régions tempérées, peu de différences apparaissent toutefois quant à la qualité de la MOS sous ces climats différents. La stabilité de l'agrégation est plus élevée pour les sols des régions intertropicales, ceci étant probablement dû à leur minéralogie dominée par des argiles de type 1:1 associés à des oxihydroxides métalliques. Toutefois, pour les sols tropicaux, la corrélation entre teneur en C et stabilité de l'agrégation est plus faible et de moindres quantités de C sont associées avec les éléments fins (argile+limon). Aussi bien sous climats tempéré que tropical et subtropical, une augmentation générale des stocks de C du sol (≈ 325 ± 113 kg C·ha -1 ·an -1 ) est observée avec les pratiques de non labour. Pour les sols des régions tempérées, si une fixation de CH 4 (≈ 0.42 ± 0.10 kg C-CH 4 ·ha -1 ·an -1 ) est mesurée sous non-labour, parallèlement une émission de N 2 O est observée (≈ 1.95 ± 0.45 kg N-N 2 O·ha -1 ·an -1 ), conduisant finalement à un bilan négatif en terme de réchauffement global exprimé en équivalents de flux de C-CO 2 .carbone du sol / agrégation / émissions N 2 O / non-labour / régions tempérées et intertropicales INTRODUCTIONThe conservation of sufficient soil organic matter (SOM) levels is crucial for the biological, chemical and physical soil functioning in both temperate and tropical ecosystems. Appropriate levels of SOM ensure soil fertility and minimize agricultural impac...

Changes in soil organic matter under different land management in misiones province (Argentina)

“…Working in similar soils of Misiones, Morrás & Piccolo (1998) found more aggregation and more SOM in the top 0.05 m of the soil and more aggregation degree but no differences in SOM content at 0.05 -0.15 m soil depth after six years of elephant grass -yerba mate association as compared to a long term conventionally tilled yerba mate plantation. In contrast to temperate soils, the better aggregation in tropical soils does not lead to an increase in C sequestration: aggregates formed by mineral-mineral bindings form faster but also protect less C upon conversion to no tillage than aggregates in temperate soils (Six et al, 2002).…”

“…Its combination with a simple model to describe decrease C kinetic from forest and accumulation C kinetic from elephant grass is promising. Although the descriptive model we used is easier to parameterize than other more powerful models which describe SOM bio-transformations taking into account a great number of parameters and compartments (Smith et al, 1997;Nicolardot et al, 2001;Petersen et al, 2005), the validation of this one in other experimental sites of the Ultisols of Misiones province is still pending. Thus it should be used carefully in long-term simulations, due to the need of continuous experimental data, particularly to establish the stable SOM pool size.…”

Carbono e nitrogênio nas frações granulométricas da matéria orgânica do solo, em sistemas de culturas sob plantio direto

“…A principal função da MO particulada é servir como fonte de energia e nutrientes aos organismos, o que desencadeia os processos de formação e estabilização dos agregados, transformações bioquímicas dos elementos e aumento de cargas no solo (Duxbury et al, 1989;Baldock & Skjemstad, 2000;Six et al, 2002a). A entrada e a maior concentração de MO particulada ocorrem, principalmente, nos primeiros centímetros abaixo da superfície do solo, sendo diretamente influenciadas pela serapilheira e raízes (Duxbury et al, 1989).…”

“…A entrada e a maior concentração de MO particulada ocorrem, principalmente, nos primeiros centímetros abaixo da superfície do solo, sendo diretamente influenciadas pela serapilheira e raízes (Duxbury et al, 1989). Dessa forma, o preparo do solo, a quantidade e qualidade dos resíduos culturais, a relação raiz/parte aérea e a frequência e duração dos cultivos interferem na dinâmica e no estoque de MO particulada (Janzen et al, 1998;Balesdent et al, 2000;Six et al, 2002a;Chevallier et al, 2004;Santos et al, 2011), e, portanto, nas propriedades do solo que conferem qualidade.…”

Atributos físicos de um planossolo háplico sob sistemas de manejo comparados aos do campo nativo

“…Ci. Solo, 32:1849-1855 contribuem na agregação pela aproximação das partículas do solo (Carter, 2002;Six et al, 2002). Watts et al (1997) Em comparação aos sistemas PD e PC, o maior DMPA foi observado no CN (Quadro 2).…”