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United States Department of Agriculture

Agricultural Research Service

Title: Microbial engineering to enhance your bottom line

Author
item Nichols, Kristine

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 19, 2008
Publication Date: January 29, 2008
Citation: Nichols, K.A. 2008. Microbial engineering to enhance your bottom line. Meeting Proceedings for the 12th Annual No-Till on the Plains Winter Workshop, Salina, KS, Jan. 29-30. pp. 138-139.

Interpretive Summary: Agriculture, now and in the future, faces many challenges – rising fuel and input costs; increasing urbanization, global population, and pressure to be more environmentally sustainable; and decreasing water and soil resources. No-till systems with continuous and diverse plant cover improve soil fertility and health and can help producers face these challenges and enhance their bottom line by reducing costs while maintaining or increasing yields. The soil foodweb is a comprised of billions of different organisms – bacteria, micro-arthropods, fungi, earthworms, insects, plants and animals – interacting at different trophic levels to provide food and energy for the growth and maintenance of this diverse community. Carbon entering into this foodweb comes either directly or indirectly from the plant as plant residues or root exudates. As this carbon flows through the foodweb and is feed upon by different organisms, it changes molecular structure and eventually becomes part of humus, or decomposition-resistant organic matter, that gives the dark brown ‘richness’ or fertility to soils. Recent research has demonstrated that soil biota not only contributes to the formation and maintenance of organic matter, but organisms have also been identify as environmental engineers. As engineers, they manipulate their environment to increase their access to food and support greater growth. The formation and stabilization of soil aggregates (i.e. soil pellets larger than 0.098 inches) is a prime example of microbial engineering. Soil organic matter transformations, as a result of soil biological activities, play a major role in the aggregation process. These activities, especially the growth of fungal hyphae, arrange primary particles (i.e. sand, silt, and clay) into conglomerations which are glued together and stabilized by bacterial and fungal metabolites/exudates. Soil aggregates then act homes for microbes which provide protection against predators and movement by soil water, and contain organic matter (or a microbial food source). Soil aggregates also improve soil porosity which improves air and water movement into the soil. These processes enhance microbial growth by providing much need water and oxygen and reducing toxic carbon dioxide concentrations. Modern agricultural practices, such as tillage and high fertility inputs, have destroyed the environment favorable to microbial growth by mechanical shearing aggregates, exposing buried humus to the soil surface where it is more rapidly decomposed by exposure to air and residue decomposers (i.e. microorganisms on the soil surface which feed on crop residues), and reducing root exudates which are an important source of food in the foodweb. These factors create a vicious cycle of microbial and aggregate loss due to increases in microbial habitat destruction and predation, and decreases in microbial food supplies and exudates. Without the input of fungal hyphae and fungal and bacterial exudates, new soil aggregates are not formed, and old soil aggregates may more easily fall apart. To rebuild microbial populations and improve soil quality, no-till, continuous cropping production systems are recommended. Increasing plant diversity is also recommended to maintain the foodweb. Plant diversity impacts the carbon to nitrogen ratio of the food source, which makes the food palatable to a variety of different organisms in the soil. Having a diverse array of organisms in the soil helps to maintain predator and prey relationships, favors improved soil fertility and reduces risks from diseases and extreme weather patterns, such as drought, flooding, and changes in temperature conditions – intense heat or cold.

Technical Abstract: The soil foodweb is a comprised of billions of different organisms – bacteria, micro-arthropods, fungi, earthworms, insects, plants and animals – interacting at different trophic levels to provide food and energy for the growth and maintenance of this diverse community. Carbon entering into this foodweb comes either directly or indirectly from the plant as plant residues or root exudates. The microbes in this foodweb are also environmental engineers who manipulate their environment to increase their access to food and support greater growth. Soil aggregate formation and stabilization is a prime example of microbial engineering. Fungal hyphae arrange primary particles (i.e. sand, silt, and clay) into conglomerations which are glued together and stabilized by bacterial and fungal metabolites/exudates. These aggregates protected microbes on and within them from predation, loss of habitat, and loss of food or organic matter. Tillage and high fertility inputs have destroyed the environment favorable to microbial growth by mechanical shearing aggregates, exposing buried humus to rapid decomposition, and reducing root exudates. No-till, diverse cropping systems have demonstrated their ability to rebuild microbial populations and improve soil quality. Maintenance of the soil foodweb will enhance microbial engineering which may improved soil fertility and reduce risks from diseases and extreme weather patterns, such as drought or flooding.

Last Modified: 7/28/2014
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