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Soil composition
Soil develops very slowly over long periods of time, and its formation results from natural and environmental forces acting on mineral, rock, and organic compounds. Soils can be divided into two groups: organic soils are those that are formed from sedimentation and primarily composed of organic matter, while those that are formed from the weathering of rocks and are primarily composed of inorganic material are called mineral soils. Mineral soils are predominant in terrestrial ecosystems, where soils may be covered by water for part of the year or exposed to the atmosphere.
Soil consists of these major components:
- inorganic mineral matter, about 40 to 45 percent of the soil volume
- organic matter, about 5 percent of the soil volume
- water and air, about 50 percent of the soil volume
The amount of each of the four major components of soil depends on the amount of vegetation, soil compaction, and water present in the soil. A good healthy soil has sufficient air, water, minerals, and organic material to promote and sustain plant life.
The organic material of soil, called humus, is made up of microorganisms (dead and alive), and dead animals and plants in varying stages of decay. Humus improves soil structure and provides plants with water and minerals. The inorganic material of soil consists of rock, slowly broken down into smaller particles that vary in size.
The new trend of soil studies: the Inorganic Carbon
Soils are a major player in the global carbon (C) cycle and climate change by functioning as a sink or a source of atmospheric carbon dioxide (CO2). The largest terrestrial C reservoir in soils comprises two main pools: organic (SOC) and inorganic C (SIC), each having distinct fates and functions but with a large disparity in global research attention.
The Organic Carbon
Organic C is a vital component of healthy soils due to its crucial role in nutrient cycling, physical and chemical soil properties, as well as positive impact on microbial functions. This organic C is a major player in global climate change because of its dual roles as sink or source of atmospheric CO2 depending on soil management, plant biomass input, land use, and climatic conditions.
The Inorganic Carbon
The SIC pool is larger than the atmospheric CO2 pool or terrestrial plant biomass C. It is often assumed that SIC changes very slowly over geological time scales because its contribution to biological cycles is much lower than SOC.
Many recent studies, however, report that SIC is far from stable and can be vulnerable to land use changes and intensive crop production, soil acidification, and water flow and recharge – processes that can reduce and even deplete SIC stocks within a few decades.
Soil inorganic C is a major player in the global C cycle and climate change, whose contributions are mainly by releasing CO2 in the atmosphere, that must be understood to achieve mitigation goals related to global land use and climate change.
There is a considerable disparity in the level of global research attention dedicated to SOC and SIC. Although several studies have generally indicated that SIC is an overlooked C pool, but it remains unclear how much specifically SIC is understudied in global soil C research. The differences in the contributions of SOC and SIC pools in global soil C research remain to be quantified.
A vast majority of studies investigating carbon fluxes at the soil–atmosphere interface considered biogenic respiration as the main source of CO2. However, careful consideration is required while estimating the carbon budget of calcareous soils since a significant amount of CO2 emission might originate from abiotic sources.
Ignoring the impact of inorganic carbon in calcareous soil may result in an overestimation of soil respiration, particularly when assessing organic matter decomposition.
Subject to various management practices, soil carbonates could be a major source of C via dissolution and CO2 emission and, together with soil respiration, could have a significant impact on the global C balance.
How to analyse the Soil Inorganic Carbon
Soil inorganic carbon is analyzed by measuring the amount of carbon released after treating a soil sample with an acid, which converts carbonates into CO2 gas.
With our TIC DISCOVER all the process of analysis is automatic.
The instrument is equipped with an autosampler up to 68 positions which hosts 40 or 60 ml vials sealed with septum and screw cap.
After filled in the vials with the samples (up to 2 gr), the instrument starts adding automatically acid, through a probe, into each vial.
The acid reacts with the sample and release CO2 (that is the CO2 from the inorganic content).
The probe will collect an aliquot of the CO2 to inject into the basic unit, that detect the amount of carbon through an NDIR detector.
The TIC DISCOVER is a fully PC controlled instrument, with its own software Windows based.
This allows a fully unattended highly reliable automation for overnight operation.
