Soil Maps summarise available knowledge and present it in a graphical form for others to understand and use. The contents of soil maps depend on the purpose, kind, scale, intensity of sampling, soil complexity and purity of mapping units required by the land user or a project.
John Rasic has pioneered an innovative 4-step mapping system for displaying soil properties in the most meaningful way. On the basis of the presence or absence of specific soil properties determining particular land use, the system is able to rate soil advantages, limitations, suitability and potentials of a land and offer solutions for soil problems and management.
This rating provides a practical means of dealing with the complex challenges that is targeted to identifiable and measurable areas of land and, in this respect, is different to other systems in use. This system can be highly selective in data selection and presentation and is particularly useful for corporates and private enterprises. It is designed to help land users to understand and visualise what the survey land is like by answering the following questions:
- How and why are soils similar or different?
- Why are the soils grouped or separated as shown on the maps?
- What are the advantages and limitations of the soils or groups of soils?
- How can such limitations be corrected using available technology?
- How can the natural soil boundaries be relocated to reduce the contrast, not only between the soils, but also between running costs and productivity?
- How to synthesise between different soils that can sustain similar kinds of practices after amelioration?
- What will the potential of the land be after corrective measures or amelioration have been implemented?
- How to avoid the twin penalties of low returns through under-use and long-term damage from over-use?
See examples of maps below.
Map 1–Soil Types
- The extent and the distribution of different soils as they were recognised in the field during the soil survey
- The approximate boundaries or demarcation lines between areas of different soil types
The map is usually of permanent and general character, for it contains all the data available and, as such, cannot be tailored to suit the needs of a particular land user or project. Map 1 is rarely sufficient for planning and decision-making because it cannot present all of the data. However, it is very important, as it is from this map containing all the data that one derives a series of interpretive maps showing different sets of relationships between the soils and their characteristics influencing different land uses.
The main benefit of such a Base Map is the ability to store, retrieve, revise, reuse and re-interpret the data for both immediate and future land uses, but without the need for repeating the field work and data entry for the second time.
Map 2–Soil Suitability
The Soil Suitability Map (will open in Adobe Acrobat) is derived from Map 1 and is highly selective in data analysis, interpretation and presentation. This map is the first of the interpretive maps produced in the process of the 4-step mapping system and designed to:
- Identify soil properties that are both favourable and restrictive for intended land uses
- Group various soils into distinct classes called “Suitability Units”, which have one or a few quite specific but similar limitations that require similar remedies for their improvements
The main benefit of the Soil Suitability Map is to:
- Evaluate the current soil status as it is before soil improvement or amelioration
- Provide a cost estimate of the remedial work specified on the Amelioration Map, and
- Help you to decide, in the pre designing and pre investing stage, whether to proceed with the necessary soil improvements or to change plans and to find more suitable land.
Map 3–Soil Amelioration
Amelioration is a process of modifying soils to improve their usability. Rarely can we modify an entire soil profile, but only some parts of it. This modification is never cheap, simple or easy. When soils are poorly understood and treated incorrectly, irreversible damages can occur and make them worse than they were before treatments.
- Prescribe the remedies for overcoming the soil limitations shown on Map 2
- Group the soils with similar limitations into Amelioration Units that require similar corrective measures for their improvements
- Relocate natural soil boundaries and increase uniformity, not only between the soils but also between running costs and productivity
This interpretive map should always be used in conjunction with Map 2, as it is designed to minimise the risk of potentially greater expenses associated with guess work, redesigning, reamelioration and reinstalment. The main benefit of the amelioration map is to help you to make the right choices and get the best possible outcome for your money the first time round.
Map 4–Soil Potential
The Soil Potential Map (will open in Adobe Acrobat) ) is the final step of 4-step mapping system designed to synthesize between ameliorated soils and group them into broader management classes called Soil Potential Units, which can sustain similar kinds of practices after amelioration.
This highly integrative map is derived from the previous Maps 2 & 3 and is, therefore, applicable only if the proposed remedial work is fully and correctly implemented. It provides the basis for designing irrigation layout and water scheduling, selection of crops, moisture monitoring, trailing sites, benchmarking and management.
The main benefit of this map is the ability to predict, with a high degree of certainty, the soil status after amelioration.
In time, however, the condition of ameliorated soils will inevitably change, and handed over soil information should be revised as knowledge and experience progresses. An appropriate post-survey support plan can be made to deal with such changes according to the needs of your soils as describe under the heading After Handover.