ICON description and consortium

ICON major goals

The interdisciplinary and transdisciplinary research unit ICON started its operation in 2011. It carries out process-oriented re-search for exploring and quantifying the ecological consequences of future changes in rice produc-tion in SE Asia. ICON particularly focuses on the consequences of altered flooding regimes (flooded vs. non-flooded), crop diversification (wet rice vs. dry rice vs. maize) and different crop management strategies on the biogeochemical cycling of C and N, associated green-house gas emissions, the water balance, and other important ecosystem services of rice cropping systems. The overarching goal is to provide the basic process understanding necessary for balancing the revenues and environmental impacts of high-yield rice cropping systems while maintaining their vital ecosystem services. A huge field experiment has successfully been established at the Interna-tional Rice Research Institute (IRRI, Philippines), which was complemented by field and laboratory experiments. Major conclusions drawn from ICON Phase I are:

A central field experiment is established at the International Rice Institute (IRRI, Philippines). Experiments of ICON comprise

• molecular biological processes of carbon and nitrogen cycling and associated GHG exchange in soil.
• the structure and functioning of soil food webs.
• a combination of plant physiological and soil chemical research addressing the fate of root exudates in soil and their impact on carbon cycling and nitrogen retention
• high resolution/high precision assessments of carbon, nitrogen and water budgets.

Phase I of the Unit finished in 2014. Major conclusions drawn from ICON Phase I are:

• Pollution swapping based on GHG emissions seems not to be a major risk associated with crop diversification. Losses of soil organic carbon could reverse positive changes of the GWP if they exceed 0.5 t C ha^-1 per cropping season.
• Transition towards a terrestrial soil fauna occurs, but the succession did not yet reach a climax. Buffering of macro- and micro-bioturbation on the release of trace gases has the potential to diminish environmental risks.
• Microbial boosting of nitrogen cycling is small, but changes in the plant microbiome may have unknown consequences for plant-microbe interactions.
• Crop diversification reduces water retention with the long-term balance depending on climatic fluctuations. Crack dynamics seem to be the critical driver of hydrological cycling.
• Loss of organic matter and nutrients are among the major drawbacks of crop diversification. Appropriate mitigation options are needed to reduce environmental risks.
• Nitrogen fertilization is not a viable mitigation management. Alternative mitigation options need to be proved for addressing the major risks identified in ICON Phase I.

ICON Phase 2

To continue research and develop results of Phase I ICON consortium initiated implementation of the second phase of ICON. It has four major objectives:

• quantify long-term changes of environmental process associated with crop and management diversification at the local scale by making use of the ICON field experiment,
• understand crack formation and its functional conse-quences (plot scale and lower),
• extend key findings of ICON Phase I to a higher spatial level relevant for agronomic evaluations and management decisions (regional scale) by including addi-tional representative rice-growing environments of the Philippines, and
• investigate the potential of rice straw residue management and cover crops as alternative mitigation options.

ICON consortium