Amelioration Strategies for Combating Global Soil and Land Degradation by Agroecosystems.
Alvin Smucker, Michigan State University, Crop and Soil Sciences, 530 Plant & Soil Sci. Bldg., East Lansing, MI 48824-1325 and Rainer Horn, Institute of Plant Nutrition and Soil Science, CAU Kiel, Hermann-Rodewald-Str. 2, Kiel, 24118, Germany.
Increasing numbers of rural economies tied to world markets are causing more marginal lands to be intensively managed for production agriculture. In the search for greater land area, more forests and grasslands are subjected to logging, burning and/or tillage. Potential consequences of these deforestation trends include greater surface erosion of marginal soils along sloping landscapes devoid of protective vegetation. Reductions in soil health, structure stability, and increased greenhouse gas emissions coupled with surface soil losses cause irreversible damage to the landscape and the atmosphere. This symposium will focus on the theoretical and practical approaches for new and novel reclamation strategies that reverse soil degradation processes. Specific tools, practices and methodologies that promote the maintenance and regeneration of soil resources located on multi-use landscapes while increasing agriculture-based income without damaging the environment will be presented. Feed back and feed forward mechanisms associated with aggregate stability, water infiltration, surface vegetation, and soil health will be discussed. Intensive tillage practices reduce Soil Organic Matter (SOM) contents leading to soil degradation and erosion. Soil aggregate complexes are among the most active biogeochemical structures known. The majority of soil profile volumes are tightly packed with these highly interactive structural sanctuaries which establish independent gradients of pores, water, oxygen, carbon dioxide, essential plant nutrients, organo-mineral complexes, and myriads of microbial communities. Recent evidence indicates that soil aggregates are clearly one of the least explored natural sites for stabilizing surface soils and sequestering additional quantities of Carbon (C) from the atmosphere. New synchrotron technologies provide non-destructive and repeated observations for identifying revised demographics of intraaggregate pores that facilitate feedback and self-organizational mechanisms for strengthening soil macroaggregates. These new biogeochemical mechanisms offer new opportunities to double or triple the quantities of soil C stored for longer periods of time by macroaggregates. Soil aggregates require frequent additions of significant quantities of C products from surface plant residues, plant roots, and decomposing particulate organic matter. Recent studies indicate that carbon deposition rates of 1300 to 1900 kg per ha are required to maintain the stability of soil aggregates, 6.3 to 9.5 mm across, when subjected to repeated drying and wetting cycles. This high C requirement suggests sustainable management systems must be designed to generate high quantities of C which stabilize surface soils.