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Applications of GIS in soil science

What is soil science? 

Officially soil science in geography is the in-depth study of soil, including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils 1. All for the purposes of improved use and management of soils.

Why is studying soil science important?

Healthy soil contributes to healthy biodiversity, which is important for us to preserve and protect. But healthy soil also helps our economy and society, how? Soil that is kept balanced and fertile will produce more crops, meaning more food to feed the worlds growing population.

Soil scientists optimize soil health that in turn boosts food production so that we can get the highest yield possible from a crop. They develop methods to combat erosion to keep river banks stable and in turn improve water quality. Soil is a non-renewable resource of which many industries are reliant upon.

They identify soil types so that land can be appropriately zoned for flood management purposes, or help us to better understand the movement of contaminants in the soil. The agriculture industry relies on soil science, as does the forestry industry, the environment, even city planners need soil science. So, how does Geographic Information Systems (GIS) and remote sensing play an integral part in soil science?    

How are GIS technologies used in soil science?

Firstly, GIS is not just the map production but the culmination of the data collection and analysis as well. GIS is often used in conjunction with remote sensing and Global Positioning System (GPS) technology to benefit soil science. Remote sensing is the process of monitoring or detecting physical changes in the earth’s properties from a distance. This often entails the use of satellite imagery, aerial imagery, ground penetrating radar or LiDAR data. These various technologies are able to detect different features and at different resolutions, depending on project budget and the detail required. Satellite imagery provides large scale imagery but with a lower resolution, whereas aerial imagery can provide really high-resolution imagery of a selected area. LiDAR stands for light detection and ranging and this process effectively creates 3D imagery of the earth’s surface. Ground Penetrating Radar (GPR) sends radar pulses into the soil to investigate underground features or the soil substrate. GPR is a non-invasive way to analyze the soil properties, and can be very cost effective 2. GPS technology then comes into play in order to link together the mapping capabilities with the imagery collected or data collected on a GPS itself. GPS can be fitted to vehicles, equipment or be hand held to collect data like digitizing boundaries or notable features. All of this remote sensing data collection can be mapped and analyzed with the help of GIS software. These computerized models then help land managers to make those informed decisions. 

GIS and soil mapping

The use of GIS in soil mapping is called Digital Soil Mapping (DSM), which involves creating geographically referenced soil databases from spatially explicit environmental features and field surveys 3.  The data that goes into creating these DSM use remote sensing technologies. Prior to the use of remote sensing, traditional soil surveys were entirely field-based and consequently were labor-intensive, time-consuming and expensive 4. A traditional soil survey would involve soil samples being collected at regular intervals throughout the plot of land. But, with advances in GIS software much can be done without the use of field surveys now. This doesn’t mean traditional soil surveys are not completely done for, as most DSM surveys will require an element of ground-truthing and hands-on data collection. However, the fieldwork is significantly reduced. Today, most soil scientists will go into the field with digital imagery already uploaded onto a rugged tablet or handheld computer. Much of the work will have already been done by the various remote sensing technologies, and all the scientist needs to do is take soil samples or photographs. 

Why do we need soil maps?

Having good quality soil maps are the baseline for many areas of land use planning and management decision making. For example, farm managers can use GIS to identify the most optimal locations for water storage solutions (e.g. dams) based on soil types and other factors. Understanding the soil substrate in an area can also help for future management and conservation of groundwater supplies. Soil maps have an exhaustive list of applications including in grassland improvement, crop yield assessments, erosion management or flood mitigation planning. 

GIS to monitor soil loss and erosion

GIS and remote sensing can be used to make estimates on soil erosion risk and land degradation status, which is important worldwide in agriculture, the environment and in urban areas. In parts of the world where soil loss is affecting people, nature and food production, information like rainfall data, soil type, land use, vegetation cover and the digital elevation model (DEM) can be combined to make an estimate of the erosion risk of an area 5.

In Australia, the health of the Great Barrier Reef is threatened, in part, by sedimentation and soil loss on land. Land managers and government there have been using a combination of airborne and land-based LiDAR surveys to assess gully erosion and target land remediation efforts 6. By doing this they hope to achieve reduced soil loss, water quality improvement and better overall grassland health. Often monitoring soil loss and erosion risk requires many years of data for comparison. High-resolution imagery is cost prohibitive for many, however further advances in technology, open-source GIS software and data collection methods means that these costs are   dropping 7

GIS and soil contamination

Soil contamination and remediation is becoming a big topic around urban areas, waste or mine sites. Contamination from metals and other substances can make the soil toxic for years to come unless the contamination can be identified and removed. One problem encountered when assessing land contamination, as similar to soil surveys, is the intensity of field work involved. By using powerful GIS software it’s possible to more precisely measure spread of contaminants, reduce the labor required in the field and target treatment methods more efficiently 8.

GIS and soil moisture

When studying and managing flood risk it’s not just the water scientists need to study but the soil. The soil substrate and soil moisture content is an important part of understanding flood risk. With climate change putting additional pressure on water resources globally, land managers and city planners must utilize all the technology available, to better understand the catchments they work in. Different soil types or substrates will hold water in different ways and it’s important to understand soil moisture content for a variety of reasons.

Most obviously, it benefits farmers to grow crops, but also helps us to understand groundwater recharge and in turn to better manage our water resources. Soil moisture data can be collected either at a small scale for specific farms or regional areas, or large scale. In 2014 NASA released global scale soil moisture maps that they compiled using satellite-based technology 9. This data has the potential to be used to monitor droughts, predict the weather and many other possibilities. 

GIS, soil science and agriculture

The agriculture sector is rapidly adopting technology and reaping its benefits, GIS is no exception. GIS has enabled farmers to increase production and yields, reduce costs and manage land resources more efficiently. Precision agriculture is commonplace in much of the developed world, with GPS and sensors fitted to tractors and other farm implements to continuously feed data back to farm managers 10. In some cases, farms today can almost be run from the comfort of a sofa – almost. 

GIS and crop production

Soil maps, combined with data recorded from remote sensors and GPS technology can drastically improve farm outputs. Remote sensing can collect data on the health of crops, soil moisture, soil temperature, soil nutrition or the presence of pests and invasive plants . This information can be combined with GIS software to develop varied fertilizing rates across a field, so that more fertilizer is distributed to the parts of the field that need it most. This enables farmers to reduce their fertilizer use, thus, saving them money and reducing the side effects of excess fertilizer run off. The same system can be applied to watering rates, pesticide and herbicide application. 

GIS and grassland management

When raising livestock in extensive production systems the grass quality is of utmost importance. Many other things will affect the production values, but the quality of their food is a high priority. Managing grasslands sustainably requires land managers to understand the soil properties that the grass grows within. Geospatial analysis can help managers determine the suitability of land types for grazing, optimal stocking rates and how the grassland will respond to different environmental conditions 13.

The future of GIS in soil science

Soil science is at the heart of numerous industries and it’s clear that managing soil sustainability offers many benefits to our livelihoods and planet. Predictions of a global population increase and the impending pressure on food production has encouraged a focus on increasing crop yields, and the sustainable use of agricultural land and natural resources. While so much has already been achieved in the realm of GIS in soil science, there’s more to come. More powerful modeling programs with greater detail and accuracy are just some of the advancements we’re likely to see in the future. 

References:

1. https://www.soils.org/files/science-policy/sssa-marketing-2013.pdf 

2. https://acsess.onlinelibrary.wiley.com/doi/abs/10.2136/sh1982.3.0017

3. https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/geo/?cid=stelprdb1254424

4. https://www.sciencedirect.com/topics/social-sciences/soil-surveys 

5.https://www.researchgate.net/publication/259360636_Use_of_GIS_and_remote_sensing_to_assess_soil_erosion_in_arid_to_semiarid_basin_in_Jordan 

6. https://www.oecd-ilibrary.org/sites/3653d3d2-en/index.html?itemId=/content/component/3653d3d2-en 

7. https://www.earthdoc.org/content/papers/10.3997/2214-4609.2020geo131  

8. https://www.diva-portal.org/smash/get/diva2:1257790/FULLTEXT01.pdf

9. https://www.integratesustainability.com.au/2018/11/23/gis-in-agriculture/