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Teagasc: Sequencing Ireland’s soil genome

The use of predictive soil mapping was necessitated by the prohibitive cost of a manual survey

Teagasc and the Environmental Protection Agency (EPA) have come together to launch the new Irish Soil Information System. In what has been described as the equivalent of "sequencing Ireland's soil genome", the new system has resulted in the production of a National Soil Map which indicates where all 213 soil types that are found in Ireland can be found throughout the country.

The 1:250,000 scale map is part of an integrated soil information system, which provides a free public web portal that gives stakeholders, including farmers and local authorities, a tool to explore Irish soils and their properties.

According to Teagasc director Prof Gerry Boyle, the new soil information system opens a new chapter for agriculture and for the environment. "For the first time, after three generations of soil science, we have a complete picture of the diversity and properties of soils in Ireland."

EPA director Laura Burke adds: "Soils are literally the foundation of our rural environment. We know that each of our 213 soil types are unique and have their own characteristics and agronomic and environmental responses. Sustainable management of this national resource is key to achieving the 'smart, green growth' envisaged in the Food Harvest 2020 Strategy.

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“Through this successful collaboration between Teagasc and the EPA,” she adds, “we are now one step closer to ensuring that Ireland’s green credentials are truly at the heart of our farming produce and our countryside.”

The new map will assist farmers in deciding how much nutrients to give their land and when as to establish what crops and other activities might perform best. It will also provide additional data to assist the EU to evaluate which farms qualify for additional special assistance due to poor quality soil and other criteria.

There are also significant environmental benefits, notably in the area of water quality. The water framework directive in Europe aims, inter alia, to achieve at least "good" water quality status by 2015 by mitigating the causes of pollution and these include the migration of soil nutrients into river basins.

However, many catchments may not achieve good water quality status within this timeframe due to the time lag of nutrient transport from source to receptor. This delay reflects the time it takes for nutrients to travel to the water body via hydrological and hydrogeological pathways and can range from days to decades. The new map will help with an appraisal of the time lags which apply to differing areas and soil types throughout the country.

Another important environmental consideration is the potential of soils to act as a carbon sink offsetting greenhouse gas emissions. With agriculture accounting for 40 per cent of these emissions, there is a clear challenge to increase production in compliance with climate change targets. In addition, both markets and consumers are demanding that agricultural produce generates lower carbon footprints.

The capacity for the sector to reduce greenhouse emissions through abatement measures is limited to about 8 per cent of current emissions, but soils can play an important role as a potential carbon sink.

Indeed, European temperate grasslands have been shown to be a carbon sink, with annual sequestration rates of approximately 1 tonne of carbon per hectare.

Given that grassland comprises 4 million hectares, or 90 per cent of this country’s agricultural area, the size of Irish grassland sinks may be considerable. The enhanced soil quality information should help improve the performance of Irish grassland as a carbon sink.

"Knowledge of the location and properties of soils will allow for more precise and effective policies", says Reamonn Fealy of Teagasc's Spatial Analysis Unit. "Already the Department of Agriculture, Food and the Marine is using the new maps to delineate the new areas of natural constraint.

“Similarly,” Fealy adds, “the soil information system will facilitate more targeted and effective implementation of the river basin district management plans, and a progression towards tier-3 reporting on greenhouse gas emissions. More targeted policy approaches will result in more synergies between increased food production and environmental sustainability”.

The initial work on the new map actually started more than 40 years ago when Teagasc’s predecessor, An Foras Talúntais, carried out the first soil survey in the 1970s. This survey mapped the soils of approximately half of the country and the detailed county maps produced from it have been in great demand ever since from scientists, planners, local authorities and indeed farmers.

The Irish Soil Information System represents an infill of this data to create a map for the whole country.

"Using the historical data collected by An Foras Talúntais, we created soil landscape models called 'soilscape' models," says project manager Dr Rachel Creamer. "These allowed us to predict the soils in counties that had not yet been surveyed. We then conducted a traditional three- year survey campaign to validate the predicted map in over 10,000 locations."

The Teagasc team adopted a unique methodology that combines novel digital mapping techniques with traditional soil survey application in collaboration with Cranfield University in Bedfordshire, where the technology was piloted.

According to Creamer, the use of predictive mapping to create a soil map is a novel method and Ireland is the first country to use this method on a national scale. “We use the soils information that we have to predict what soil types will exist in other locations,” she says. “We have 30 different types of data relating to the soil type and we can use this to create a model to say where certain conditions exist certain soil types should.”

This predictive mapping method was necessitated by the prohibitive cost of a manual survey. “Traditional survey methods are very labour intensive and it would have been too expensive to put the boots in the field to do it,” Fealy adds.

The predictive mapping was validated by a traditional soil survey carried out over 2½ years. This validation involved the collection of soils data at more than 11,000 locations across the country. A second detailed survey was then conducted, in which dug 225 soil pits were dug, to describe these reference soils in full detail.

These pits were sampled at various depths and a suite of laboratory analyses were conducted to allow the classification of the soils, using both the Irish classification system and the world reference base system, the main unifying classification system used in Europe. These analyses included: pH, texture; organic matter; total nitrogen; extractable iron and aluminium; bulk density; and base saturation. These surveys revealed that an accuracy level of 78 per cent, which is in line with international norms.

“It’s very complex,” says Fealy. “There are 11 main soil types in Ireland and you can find nine of them in one field in Co Cork. Overall there are 213 different soil types and, while we can’t tell you exactly where you will find them, we can tell you where you are most likely to find them.

“This is very important as there is an old proverb which says that mankind owes its existence to a few centimetres of soil and the fact that it rains.”