Agronomy Research Expertise in Montpellier and Languedoc-Roussillon (South of France)

Agronomy : crops and cropping systems

Keywords :

Direct seeding mulch-based cropping systems (DMC) and carbon sequestration

2. Minimizing the impact of cropping on biogeochemical cycles

2. Minimizing the impact of cropping on biogeochemical cycles

Growing cover crops to restore degraded soils (Yunnan province, China). - A.Chabanne © CIRAD Soils contain more carbon than terrestrial vegetation and the atmosphere combined. They hence represent a critical carbon sink that is closely dependent on land-use patterns. Agricultural practices contribute to the depletion of organic carbon resources. At the plot level, the decline in carbon stocks is attributed to three processes: 1) oxidation due to the loss of soil cohesion, thus exposing carbon to temperature and humidity variations, 2) transfers such as leaching and translocation of dissolved organic carbon or particulate organic carbon, and 3) water and wind erosion. It is thus essential to increase soil organic carbon levels so as to ensure sustainable agricultural management.

DMC with high annual carbon inputs can rectify degraded agricultural soils, restore their fertility and promote overall diversity (production, soil macro- and micro-fauna). In humid tropical conditions, regeneration of the organic matter and physical and biological properties of soils can be as substantial and rapid as losses due to continuous intensive tillage. Between 10 and 15 t/ha/year of dry matter residue must be input into the system, depending on the extent of chemical fertilization, to maintain a stable carbon balance. The best DMC produce between 15 and 28 t/ha/year of dry biomass, thus enhancing organic matter regeneration, improving the physical (aggregation, infiltration), chemical (cation exchange capacity, nutrient recycling, buffering capacity) and biological (macrofauna and microbial population diversity) features. These systems which are founded on high annual biomass production and increased functionnal diversity (even in the dry season) have higher carbon sequestration capacities than the conventional systems.

Lucien Séguy,
& Florent Tivet,

Publication date: 30/05/2010



Update on 19/04/12


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