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Waters are thanking structure lime – a comprehensive research in progress

Hanne Mäkelä (hanne.makela a nordkalk.com), 7 September 2020

Structure lime which contains active lime can effectively improve soil structure and, at the same time, reduce nutrient leakage from arable lands into water bodies. Structure liming also increases the pH of soil and even reduces the fuel consumption of a tractor. The performance of the method and its suitability in various conditions is being examined as part of a comprehensive Finnish project.

The spreading team of Vesa Tuominen, a liming contractor with new spreaders, is spreading lime on the freshly harvested stubble field of Seppo Hakala, a farmer from Eurajoki Municipality. Externally, the work looks like the traditional autumn spreading of agricultural lime on stubbles; however, something new is happening now.

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The purpose of the structural liming is to improve the soil structure and thereby reduce soil erosion and the phosphorous leakage to waterways.

“We are experimentally spreading structure lime on a clayey field,” said Juha Kääriä, Senior Teacher at Turku University of Applied Sciences. “The purpose of the structural liming is to improve the soil structure and thereby reduce soil erosion and the phosphorous pollution of waters, which is the nutrient leakage from agriculture. We assume that structural liming will reduce phosphorous leakage by 30-50 per cent.”

Mr Kääriä is the Project Manager of the Structural Liming as a Method for Water Protection in Agriculture project led by Turku University of Applied Sciences. The project is part of the comprehensive Program for Improved Water Protection 2019-2023 funded by the Ministry of the Environment.

Using structure lime, positive experience and research results are seen in Sweden with the rapid reduction of nutrient input. In Finland, the use of structure lime for this purpose has so far been limited due to the lack of information and guidelines on how much structure lime should be used on various clay soils.

The suitability and efficiency of the method in Finland is now being tested within this comprehensive research, which is also connected to the spreading of structure lime in Eurajoki. In Finland, most clay soils are situated in Southwest Finland and the Uusimaa regions.

Benefits for both waters and farmers

The project involves research on the performance and suitability of structure lime in various conditions and on different soils as well as its impact on the environmental load on waters, its impact on soil and crop yields and the determination of the optimal use volumes and spreading times.

Within the project, which will continue until the end of next year, the various impacts of structure lime are investigated in addition to laboratory and field tests from a wider pilot test performed on the drainage basin level within the drainage basins of two rivers in Eurajoki.

Structure lime contains the same amount of calcium carbonate as agricultural lime, but with the addition of a proportion of active lime that reacts with clay and improves the soil structure. Therefore, structural liming also reduces soil acidity like normal agricultural liming.

“Swedish farmers have noticed that loosening the soil structure reduces the drawbar pull caused by soil during tillage,” Juha Kääriä emphasised. “For a farmer, this means, among other benefits, savings on fuel costs.”

As part of the project, relevant drawbar pull tests are in progress in the Sugar Beet Research Centre. Test results are expected to become available this year.

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Juha Kääriä is the Project Manager of the Structural Liming as a Method for Water Protection in Agriculture project led by Turku University of Applied Sciences

Treatment differs from gypsum

The Finnish government is investing in the improvement of the environmental conditions of waters through a large gypsum treatment project. Juha Kääriä said, however, that gypsum is not suitable for all arable lands, for instance, those situated in drainage basins of high-nature-value waters or in groundwater zones. The treatment must also be renewed quite often, every 3 to 5 years.

“In contrast,” he pointed out, “structure lime is suitable for almost all but organic farming fields. Swedish studies suggest that it must be spread very rarely, that is to say, there is a substantial difference in the frequency of spreading. On some parcels in Sweden, the effect of structural liming was visible even 40 years later.”

Project results on the implementation of structural liming on various clay soils will be published in a practical manual for farmers and advisers.

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