11 Soil Restoration Technologies and their Uses, Characteristics Explained
Soil restoration technologies are infrared spectroscopy, moisture sensor, digital colorimeter, laser diffractometry, penetrometer, irrigation technology, bioreactor, pneumatic decompaction technology, desalination technology, IoT, GPS and remote sensing.
They can be broadly categorized into analytical, implementation and monitoring technologies.
This article discusses the technologies of soil restoration, as outlined below;
-Analytical Soil Restoration Technologies
-Implementation-related Soil Restoration Technologies
-Monitoring-related Soil Restoration Technologies
-Soil Restoration Technologies and Methods/Techniques for Various Scenarios
-Analytical Soil Restoration Technologies
The analytical soil restoration technologies include technological tools and equipment that are used to evaluate of analyze soil.
These technologies are useful in reconnaissance study of sites where environmental degradation has occurred, to collect information regarding the nature and severity of degradation.
The information that is collected using these technologies, may serve as a guide when making decisions on the soil restoration methods that will be implemented.
Analytical soil restoration technologies are; infrared spectroscopy, soil moisture sensor, digital colorimeter, laser diffractometry, and penetrometer technology.
1). Infrared Spectroscopy as one of the Soil Restoration Technologies
Infrared spectroscopy is one of the most common technologies used in soil restoration projects.
It is an analytical technique, and the basic principle behind infrared spectroscopy is to evaluate and characterize soil properties based on how the soil interacts with radiant energy [11].
There are various soil attributes that can be investigated using infrared spectroscopy. These include structural configuration, mineral composition, presence of pollutants and degree of degradation.
Evaluating these attributes is helpful for gathering information about the soil that can be used subsequently in the restoration process.
In infrared spectroscopy, a sample of the soil is introduced into an apparatus which is generally equipped with a projector which directs radiant energy toward the sample, and a spectrometer which measures the pattern of interaction between the radiant beam and the sample.
Expert knowledge is usually required to interpret the data derived from using this technology, in order to gather useful information about the soil being analyzed.
The results of analysis using infrared technology are relatively reliable, and the technology itself is simple, nondestructive and fast to use [15].
There are various types of infrared technologies that are used to analyze soil. These include Fourier Transform Infrared (FTIR), visible-Near Infrared (vis-NIR), Mid-Infrared (MIR) and Photoacoustic Spectroscopy (PAS) [14].
2). Soil Moisture Sensor as one of the Soil Restoration Technologies
The soil moisture sensor is a hydro-sensitive technology that is designed to detect and estimate the volumetric quantity of water in soil [5].
There are various forms in which soil moisture sensor technology can be designed. The sensor may take the form of a portable handheld device or a more elaborate, larger and stationary system.
Soil moisture sensors mostly function based on electric conductivity, whereby the conductive quality of the water in soil is used to detect and quantify it.
The relevance of soil moisture sensor technology ranges from environmental remediation to sustainable farming, resource conservation and soil rehabilitation.
In soil restoration, moisture sensors may be used both in analysis and monitoring of soil.
3). Digital Colorimeter as one of the Soil Restoration Technologies
The digital colorimeter is a technological instrument that is equipped with photometric sensors that can analyze the characteristics of soil through its optical properties.
In order for soil to be analyzed with a colorimeter, it must be suspended in a soil-water solution. The colorimeter may project a beam of light through this solution, then measure and compare the amount and color of light that passes, to a given standard. This standard is often the light amount and color transmitted through a pure solvent under the same circumstances.
Digital colorimeter technology has the advantages of being easy and fast to use, with a fair degree of accuracy.
The technology is utilized in various aspects of soil analysis as well as monitoring. It is a component of kits used to test soil respiration, particle size distribution, soil organic carbon, and other physicochemical parameters [4]. In such applications, the colorimeter is used alongside other equipment like probes and sample containers.
Digital colorimeters operate optimally within a specified range of conditions like temperature and humidity. This range must not be exceeded in order to ensure that measurements are accurate.
4). Laser Diffractometry as one of the Soil Restoration Technologies
Laser diffractometry is a technology which entails the use of laser diffraction method (LSM) to evaluate or analyze a sample.
In laser diffractometry for soil restoration, a laser diffractometer is used to project a parallel monochromatic beam of light onto a sample of soil.
The soil is usually mixed with water to form a soil-water suspension in a sample holder or container. This enables the monochromatic beam to interact effectively with the particles of the soil.
Aside monochromatic light, x-rays may be used in diffraction analysis, to identify minerals in soil. In this case it may be referred to as “x-ray diffractometry” (XRD) [7].
The principle behind diffractometry is very similar to that behind infrared spectroscopy, which is to analyze soil characteristics based on the interaction of soil particles with radiant energy.
In diffractometry, the area of focus is particle size characteristics [12]. This includes distribution of particles and the spatial relationship between these particles.
Based on the manner in which the incident radiation is diffracted by the sample, particle characteristics of the soil can be evaluated. In restoration projects, analyzing particle characteristics is useful to determine the degree and nature of degradation of the soil, and the best methods of remediation that can be used.
5). Penetrometer Technology
Penetrometer technology relates to mechanical devices that are used to test soil resistance to penetration or vertical force.
These devices are collectively called “penetrometers” and may come in various designs according to specific needs. A penetrometer may occur as a portable handheld device that can be used in the field (in situ, onsite), or as a stationary device used in the laboratory.
As a soil restoration technology, a penetrometer is used to evaluate two main characteristics, which are; soil texture and degree of compaction.
These two characteristics can indicate the nature and severity of soil degradation, and can provide guidance on the best soil restoration methods to be used.
-Implementation-related Soil Restoration Technologies
These soil restoration technologies are those which are used during the actual process of stage of soil restoration. The implementation-related soil restoration technologies to be used on any specific site or project, are selected based on information that is gathered from soil analysis.
They include; irrigation technology, bioreactor technology, pneumatic decompaction, and desalination technology.
6). Irrigation Technology as one of the Soil Restoration Technologies
The implementation of irrigation technology is recommendable for soil restoration projects where the soil has been affected by desertification or salinization.
In desertification-related cases, irrigation moisturizes the soil and facilitates biological activity of microbes and plants, as well as carbon sequestration, thereby helping to mitigate the effects desert development and climate change on soil.
In cases where the soil has high saline concentration, irrigation technology may provide water which will eliminate the excess salts through dissolution, in what is called the “leaching fraction” technique [8].
Irrigation technology may take any of various forms. It may consist of an elaborate network of conduits, sprays, and pumps. In other cases, irrigation technology may include sensors and artificial intelligence units that automate the irrigation process [9].
The implementation of irrigation technology often requires careful assessment of the needs of the soil, in order to prevent over saturation or formation of precipitates.
7). Bioreactor Technology as one of the Soil Restoration Technologies
Bioreactors are used in soil restoration projects where bioremediation is needed.
This technology is related to other sustainable technologies or concepts like waste-to-energy, biomass conversion and biofuel production [17].
In remediation of soil, bioreactors can be used to culture microbe populations that will be introduced into a degraded or contaminated site (this act is called bioaugmentation). The bioreactor can be used to regulate the conditions under which these microbes are grown, so as to ensure that these conditions are optimal. An approach such as this is particularly effective for soils that have been degraded as a result of hydrocarbon pollution [3].
Bioreactor technology can also be utilized in composting [16]. The reactor can facilitate quality compost production, which can be applied to degraded soils in order to rehabilitate them.
8). Pneumatic Decompaction Technology
Decompaction technology is needed to restore soils which have undergone excessive compaction as a result of mechanical stress and disturbance from heavy objects over a period of time.
The implementation of pneumatic decompaction becomes necessary only when analysis (likely using a penetrometer) indicates that the soil is excessively compacted.
Compaction is itself a major problem, because it reduces soil porosity and permeability, thereby eliminating useful organisms and processes that are essential to soil health.
The principle of pneumatic decompaction is to create fractures and physically loosen compacted soil. It is often implemented alongside other practices like compost or fertilizer application.
9). Desalination Technology as one of the Soil Remediation Technologies
Desalination is a process by which minerals and salts are removed from a substance or medium, such as soil or water [2].
Water desalination is relatively common as a means of making saline water to be usable for domestic purposes. The process generally transforms saltwater to distilled water using either of two main technologies; thermal distillation and membrane distillation.
Thermal distillation involves the use of heat to separate the pure water molecules from the dissolved salt through boiling and evaporation. Membrane distillation is the use of pressure and a semi-permeable membrane to remove the contaminant minerals from water. It may be alternatively referred to as reverse osmosis, although both concepts are slightly different from each other [10].
In soil desalination, the aim is to reduce the concentration of minerals and salts in soil.
The soil restoration technology for desalination is called soil washing (also soil flushing, soil leaching). It involves the physical washing, flushing or scrubbing of soil to remove dissolved salts and other contaminants, and is mostly used for heavy metal removal [6].
Soil desalination can be carried out in situ (onsite) or ex situ (in external environment, offsite). In situ desalination is called soil leaching, while ex situ desalination may be called soil washing or soil flushing.
Soil desalination technology is water-based. The amount of water and the mechanism of salt removal are usually decided based on the type of salts in the soil and their concentrations. Desalination technologies may also be equipped to treat wastewater after the desalination process.
-Monitoring-related Soil Restoration Technologies
These technologies are used to monitor the progress and effectiveness of soil rehabilitation. They include; IoT, GPS, and remote sensing.
10). IoT Sensors as one of the Soil Restoration Technologies
IoT (Internet of Things) technology is used to control smart devices that can measure and analyze various soil characteristics [1]. This technology is used as the basic framework of artificial intelligence and smart house systems.
The effectiveness of IoT for soil restoration monitoring projects is mainly due to the ability of the technology to collect soil data on a repetitive and continuous basis. IoT can be used to control various sensors like soil moisture sensor and colorimeter. It can also be used to schedule the maintenance of soil through irrigation and fertilizer application.
11). GPS and Remote Sensing Technology
GPS (Global Positioning System) and remote sensing technology can be used to monitor soils after restoration has been carried out [13].
The productivity and health of the soil can be monitored with this technology, based on the rate of plant growth.
Soil Restoration Technologies and Methods/Techniques for Various Scenarios
The following table shows the suitable techniques, methods and technologies of soil restoration for different scenarios and soil conditions;
| Soil Condition | Restoration Method/Technique | Restoration Technology |
| Low Fertility (due to leaching and erosion) | Fertilizer Application
Organic Composting Drip Irrigation Mulching Crop Rotation Cover Cropping Nitrogen Fixation Revegetation, Reforestation Controlled Grazing |
Bioreactor Technology
Irrigation Technology Soil Moisture Sensor IoT and GPS |
| Desertification | Revegetation, Reforestation
Drip Irrigation Fertilizer Application Controlled Grazing |
Irrigation Technology
Soil Moisture Sensor Digital Colorimeter IoT and GPS |
| Hydrocarbon Pollution | Biostimulation, Bioaugmentation
Phytoremediation Organic Composting |
Bioreactor Technology
IoT and GPS |
| Salinization | Desalination | Desalination Technology
Irrigation Technology Digital Colorimeter Laser Diffractometry Infrared Spectroscopy IoT and GPS |
| Heavy metal Contamination | Biostimulation, Bioaugmentation
Phytoremediation Organic Composting
|
Bioreactor Technology
Soil Washing, Soil Flushing, Soil Leaching IoT and GPS |
| Compaction | Decompaction
|
Pneumatic Decompaction
Penetrometer Technology IoT and GPS |
Conclusion
Soil restoration technologies are;
- Infrared Spectroscopy
- Soil Moisture Sensor
- Digital Colorimeter
- Laser Diffractometry
- Penetrometer Technology
- Irrigation Technology as one of the Soil Restoration Technologies
- Bioreactor Technology as one of the Soil Restoration Technologies
- Pneumatic Decompaction Technology
- Desalination Technology as one of the Soil Remediation Technologies
- IoT Sensors as one of the Soil Restoration Technologies
- GPS and Remote Sensing Technology
References
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