Ecological engineering

Designing cropping systems based on ecological intensification

Biodiversity (plants, fauna and microbial communities) is the engine that drives soil-crop interactions and enhances ecosystem services (regulation and provision).

Direct seeding Mulch-based Cropping systems (DMC) are part of Conservation Agriculture practices, optimizing their performances. Under DMC, the three technical principles of Conservation Agriculture (minimum soil disturbance, permanent soil cover and crop rotations) are translated into biological processes with high and diversified biomass-C inputs from crops and key cover crops, to continuous C supply above and belowground, to ecosystem services of regulation and provision (i.e., SOC accumulation, improving water infiltration and retention, improving nutrient cycling, and soil biota) (Séguy et al., 2010).

Mimicking a natural ecosystem

They are built on a wide functional diversity (i.e., plant species and genetic variation within species, macro and microorganisms) to build ecological resiliency. DMC aim at enhancing the ecological efficiency of agro-ecosystems by optimizing bio-geochemical processes, through diversified crop rotations and the use of a large diversity of crops and cover/relay crops. They enhance the production of biomass (above and belowground) sustaining a continuous supply of fresh organic matter, sustaining plant nutrition, soil biological activity and microorganisms nutrition, enhancing water retention, nutrient cycling, soil functional diversity, and thus resilience to economic and climate uncertainties (Séguy et al., 2001, 2006, 2009, 2012).

 

DMC systems must first improve, restore and maintain the productive capacity of the soil while reducing the use of chemical inputs in a protected environment (i.e., control soil erosion at field and landscape levels). Maintaining soil biodiversity and soil functions are essential for improving both productivity and food stability while preserving the quality and quantity of ecosystem services in a sustainable way.

Key principles to drive ecological processes and functions, through beneficial biological interactions and synergies, are:

      • a high and continuous production of above and belowground biomass, even in poor soils, through the use of a large diversity of plants enhancing various ecosystem services,
      • keeping the soil permanently covered, maintaining through the litter system a continuous supply of organic compounds enhancing the dynamics of water and nutrients,
      • sustaining as an energy source the biological regulation by macro and microorganisms, able to perform various functions (i.e., bioturbation, chemical transformation, aggregation, biological nitrogen fixation…).

 

     
 Rolling cover of millet  Root systems of finger millet and pigeon pea  Stylosanthes guianensis

 

A large diversity of DMC systems and technologies

We develop a range of DMC systems for contrasted biophysical conditions in Kampong Cham (Red Oxisol, 70% clay), Kampong Thom (irrigation scheme of Stung Chinit, sandy soil, 80% sand) and in Battambang (alcaline Mollisol). DMC systems are designed and assessed for the main uplands crops (i.e., maize, cassava, soybean, mungbean, rice) and for lowland rice. In addition, a large diversity of plant species are used through complex rotations, associations and sucessions.

 
 A soil mining attitude in the uplands of Cambodia  Maize and cassava, the crops of the pioneers
     
Building soil resilience  through DMC systems