Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 22, 2009
Publication Date: September 10, 2009
Citation: Nichols, K.A. 2009. Soil Biological Engineering to Enhance your Bottom Line. Meeting Proceedings. Interpretive Summary: Limitations in soil quality are the biggest barrier to higher crop yields particularly for farmers in sub-Saharan Africa and south Asia, and modern agricultural practices put a great strain on the soil often resulting in the loss or extreme degradation of its organic layer. It is estimated that since land was first cultivated, the amount of C lost to the atmosphere from this organic layer is 30 to 60 Mg ha-1. This C supports of growth of organisms that enrich soil and make it more productive. The value of the services provided by the belowground community is significant and has been estimated at US $1.5 trillion annually. To maximize the gains received from these service, a system must be formed which provides the most benefits at the least cost. The formation of soil aggregates is one of the services provided by soil organisms to maximize the efficiency of a crop production. A favorable environment for plant growth comes from having an adequate amount of pore space for root growth without compaction and water and air flow. In semi-arid environments, soil aggregates will maintain pore space to capture every raindrop where it falls while the discontinuity between pore space in and around aggregates will assist in water retention by making it more difficult for water to be conducted to the surface in response to evaporative pull. In sub-humid environments, soil aggregates will assist in water infiltration which will reduce ponding and run-off. The pores created with soil aggregation also allow for gas exchange between the soil environment and the surface to support the growth and respiration of plant roots. The bottom line is no matter where you live or what you want to produce a healthy soil results in a healthy plant which produces a healthy pocketbook. Soil aggregation is a feat of biological engineering which is a major component for achieving healthy soils.
Technical Abstract: Despite the importance of soil to all life on Earth, soil is the not-well-understood ‘big black box’. Therefore, the next revolution in agriculture needs not to be a green revolution or an iron (i.e. equipment) revolution; it needs to be a brown revolution. In this brown revolution, the root of the problem is the root of the solution, namely plant roots. Throughout the growing season, it is estimated that a quantity of carbon (C) equal to about 100 to 1000 kg ha-1 or 10 to 35% of the total C assimilated by arable crops is released into the soil as root material, exudates, and other soluble products (Juma, 1993). This photosynthetically-derived carbon is used by plants as the ‘currency’ to ‘purchase’ nutrients from the soil via soil organisms. The diversity of these organisms far exceeds any aboveground ecosystem, even that of a tropical rainforest. In 1990, DNA-based methodologies estimated about 4000 different bacterial genomes per gram of soil, but more recent studies and models have pushed the number up to as high as 830,000 (Dance, 2008). Many species may be redundant – eating the same foods and fulfilling the same ecosystem jobs, but as stated above, ‘nothing is discarded’ and ‘nature practices complete continuity and complete conservation’. This cycle of materials through the interplay of the biological, physical, and chemical components of soil may continue uninterrupted, but it may be altered by the way in which soil is managed and this, in turn, will impact the products which come out of this cycle.