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Pharma Tech Outlook | Thursday, June 30, 2022
Soil microbiomes with distinct assemblies through vertical soil profiles drive the cycling of multiple nutrients in reforested ecosystems
FREMONT, CA: To combat the plethora of issues cropping up as a result of poor soil health, some European companies are developing microbial solutions that improve soil fertility more sustainably. Spain has welcomed these companies with open arms, with living organisms designed to act as biofertilizers starting to be accepted on the market.
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Humans have drastically transformed Earth’s protective soil layers, with agriculture and mining being among the most damaging land uses. Severe disturbances to soils result in their failure to hold water and recycle nutrients, two critical soil functions to mitigate biogeochemical and hydrological imbalances on a global scale. Well-established interactions among plant roots, fungi, bacteria and micro and macrofauna are all destroyed once vegetation is removed and soil is upturned, buried, or eroded.
Restoring Bio-functions to Agricultural Soils
Before being converted to agriculture, soils are endowed with vital stocks of organic matter, a dark, amorphous substance built up over decades, if not centuries, by microbial decomposition of plant, animal, and microbial residues. Agricultural crop harvesting, however, prevents most plant residues from being returned to the soil, and tillage disrupts and aerates soils, causing rapid microbial oxidation of organic matter. These practices, combined with wind and water erosion, have caused native organic matter stocks to be lowered by half in agricultural soils worldwide.
To restore soil functionality, a continued supply of fresh root exudates or organic residues is essential. Additions of organic matter sustain microbial degradation of energy-rich carbon compounds to make mineral nutrients available to plants and other microbes. During the degradation of organic compounds, microbes also produce secretions that combine with less degradable residues to create stabilised organic matter. Because it acts as a water and nutrient-retaining sponge, stabilised organic matter improves microbial habitat. Thus, microbial degradative activity exerts positive feedback on soil bio-function.
Restoring Productivity to Mining-impacted Lands
Strip mining is a process where access to near-surface coal seams has impacted millions of hectares. Although government legislation in the 1970s mandated the reclamation of strip-mined lands, legal requirements are based on minimum plant cover rather than on soil properties, with the result that previous levels of land productivity are rarely achieved post-reclamation. Poor plant productivity persists because soils are mostly rocky subsoils that have been stockpiled and redistributed. Microbes in these soils have extremely poor living conditions, with very low organic matter and little access to water and air due to heavy compaction by equipment. As mineral-rich acid mine drainage (AMD) emerges and flows overland, acidic metal precipitates are deposited on the land, killing all vegetation in its wake. A characteristic feature of a barren kill zone is a red-orange surface layer of iron oxide precipitates (below pH 3) that prohibits vascular plant growth.
To improve soil functionality, one can make the most of resident soil microbes by ameliorating their living conditions, providing sufficient, but not excessive, food, air, and water and minimising habitat disruption. The use of all aspects of a soil system from its biogeochemistry to its microbial community allows her to apply highly effective restoration and improvement methods. In the future, the focus will mainly be on how their laboratory and field studies can be scaled up to larger areas under more varied environmental conditions.
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