FAQ

What is the SAVE project?
Are there risks to using gypsum?
What is the impact of gypsum on phosphorus leaching?
Does gypsum influence crops?
Does gypsum contain sulphur?
What is gypsum and where does it come from?
How is the gypsum transported to the farms?
What kind of equipment can be used to apply the gypsum?
When is the gypsum applied?
What types of fields are suitable for gypsum treatment?
Could gypsum application prevent other measures planned for the farm?
Could gypsum become a compulsory additive for farmers in the future?
How often should the gypsum application be repeated?
Will the application of gypsum impact EU subsidies?
Why is there another study on gypsum application when this has been studied before?

What is the SAVE project?

SAVE is a joint research project of the University of Helsinki and the Finnish Environment Institute (SYKE), for the purpose of determining whether gypsum could be used as a large-scale method for waterway protection. The research entails a gypsum pilot project in the Savijoki river basin conducted in cooperation with local farmers. The project collects experiences from farmers and studies the impact of gypsum on the waterways and nutrient levels in the soil. SAVE is funded by the Finnish Ministry of the Environment (2016–2018). Pilot Gypsum is also a part of the NutriTrade project (2015–2018) funded by the EU Central Baltic programme.

Are there risks to using gypsum?

As gypsum contains calcium, it should not be used on cropland where the ratio of calcium to the other soil cations (Mg, K, Na) is already high. Cation imbalance can weaken the fertility of the soil. The applicability of gypsum is determined for each plot by checking the cation values in the productivity information of the plot. However, in most cases, the calcium in the gypsum improves the aggregate structure of the cropland and its fertility by balancing the cation ratio in the soil. Gypsum has no impact on soil acidity.

As gypsum is highly soluble, it is easily rinsed away in the runoff. Calcium is not detrimental to an aquatic environment, but high concentrations of sulphate can damage aquatic organisms. It is unlikely that the application of gypsum would elevate the level of sulphate in streams or rivers high enough to burden organisms. The project nevertheless monitors the sulphate levels in the nearby Savijoki river, and tests the impact of equivalent levels at least on greater water-moss (a type of moss common in rivers) and thick-shelled water mussels (an endangered species which may exist in the Savijoki).

In lakes, sulphate may accelerate the release of phosphorus from the sediment (i.e., “internal loading”), but there are no lakes in the pilot area. Sea water, meanwhile, naturally contains a high level of sulphate, and even extensive use of gypsum is unlikely to have any impact on the chemical balance of the Archipelago Sea. Special caution is to be exercised on fields located on potential groundwater formation areas, and if the soil is particularly permeable to water, no gypsum can be used.

What is the impact of gypsum on phosphorus leaching?

Gypsum reduces the amount of phosphorus making its way to waterways from agricultural fields, both in runoff and bound in soil. Both the calcium and the sulphate contained in gypsum increase the ionic strength of the soil, meaning that the soil particles form larger aggregates which cannot be carried to the waterways as easily with rainwater or melting snow. The calcium contained in gypsum is particularly effective at increasing the aggregate size in soil. Gypsum also facilitates the binding of phosphorus in the soil particles in a way that maintains the phosphorus available for plants. In addition, gypsum reduces the leaching of organic carbon. These effects begin as soon as the gypsum has dissolved into the soil and last an estimated 4–5 years.

Does gypsum influence crops?

Gypsum does not decrease crop yield, and may in some situations even increase it. For example, certain crucifers may benefit from the sulphate sulphur in the gypsum. With the gypsum, approximately 8kg/ha of phosphorus is introduced into the soil as “impurities”, which is a small amount considering that the gypsum is not applied annually. On the other hand, the sulphate may temporarily reduce plants’ ability to absorb selenium for the first year after application. This potential reduction in the amount of selenium must be considered if the crop is to be used as animal feed during the year following gypsum application.

Does gypsum contain sulphur?

Approximately 18% of the gypsum is sulphur. This means that for every 4,000kg of gypsum per hectare, 720kg of sulphur will be introduced into the soil per hectare. Gypsum application may help with sulphur deficiency. The sulphur included in the gypsum must be accounted for, if sulphuric fertilisers are being planned.

What is gypsum and where does it come from?

The gypsum used in the SAVE project comes from the YARA factory in Siilinjärvi, where it is a byproduct of fertiliser production. When apatite minerals (or apatite stone) are treated with sulphuric acid, phosphoric acid and gypsum (calcium sulphate hydrate, CaSO4 ∙ 2H2O) are produced. The apatite mined in Siilinjärvi contains no heavy metals or radioactive substances. This means that the calcium sulphate, i.e., gypsum, produced there is also free from dangerous substances and suitable for agricultural use. No other major sources of clean gypsum have been identified thus far, but the intention is to survey the availability of gypsum suitable for agricultural use from elsewhere during the course of the project.

The Siilinjärvi gypsum contains approximately 15% water, and has a specific gravity of 1,500kg/m3. The gypsum contains 23% calcium and 18% sulphur as well as no more than 0.2% phosphorus and approximately 0.2% fluoride as impurities derived from the fluoride apatite used as a raw material.

How is the gypsum transported to the farms?

The gypsum is transported to the farms directly from Siilinjärvi in trucks. The initial plan was to use trains for transportation. This proved to be more expensive than trucks, and would have required more loads as well as the construction of an interim storage facility. The amount of gypsum used in the project is large, but not large enough to make rail transport a cost-effective option. If the use of gypsum is adopted more widely in the future, the transportation of gypsum by rail to interim storage may prove to be a better option.

What kind of equipment can be used to apply the gypsum?

In practice, the gypsum is applied in a similar manner as agricultural lime, just at a different time of the year. The gypsum comes in a powder, like lime. Gypsum is spread evenly on the farm plots, 4,000kg per hectare. A wet lime spreader or a broadcast spreader intended for dry fertiliser can be used. Gypsum spreading equipment was tested in the TTS Work Efficiency Institute study in autumn 2008.

When is the gypsum applied?

The gypsum is applied in the autumn after harvest, before any other work on the soil. The application of the gypsum should be scheduled close to the autumn ploughing or cultivation so that the gypsum can be dissolved and mixed into the soil faster. However, gypsum can also be applied on no-till fields, if the gypsum is spread in the autumn and sowing takes place in the spring. The earliest possible moment for gypsum application is immediately after harvest. To prevent compacting of the soil, the application should be done during a dry period. Gypsum should not be spread during the winter. This is to ensure that the gypsum is dissolved into the soil and does not leach away as the snow melts.

What types of fields are suitable for gypsum treatment?

Gypsum can be used on crop fields which are ploughed or cultivated after harvesting, or on no-till fields used for spring grain.

The project excludes perennial grassland fields. Gypsum can be applied on grassland, if the field is reformed and cultivated at the time of application. As the suitability of gypsum for grassland has not been sufficiently tested, grassland fields have been excluded from this project due to its breadth. In the project, the gypsum is used primarily to protect waterways, so the fields that are of primary interest are ones with a large risk of nutrient leaching.

The gypsum used in the project does not meet the requirements set for certified organic farming, so no gypsum will be spread on organic farms. Naturally derived gypsum could be used in organic farming, but it may be difficult to acquire. The use of gypsum in organic farming will be studied more closely during the project.

As gypsum contains calcium, each field plot will be inspected to ensure it is suitable for gypsum application. For example, no gypsum should be used on over-limed fields.

Nor should gypsum be applied on no-till plots of autumn grain. If the gypsum does not fully dissolve into the soil, the sodium content of topsoil may temporarily reach levels which are detrimental to the growth of the new crop. The time needed for the dissolution of the gypsum depends on the amount of rainfall after application. Gypsum can be tested on no-till plots, if the application takes place in autumn and sowing in the spring.

Could gypsum application prevent other measures planned for the farm?

The application of gypsum results in no restrictions on other farm work. The work done by the farmers will be surveyed through interviews, so that the various measures can be considered when the project results are analysed to provide optimally reliable data on the impact of the gypsum.

In the project, farmers are recommended to plough or cultivate the soil after the application of the gypsum. This means that the gypsum will dissolve and mix into the soil faster. However, gypsum can also be applied on no-till fields, if the gypsum is spread in the autumn and sowing takes place in the spring.

Both gypsum and lime contain calcium, which must be considered if the intention is to spread both on the field. If there is no need to adjust the pH level of the field, gypsum may even prove to be a better calcium vehicle than lime. However, gypsum application will not prevent liming the field, if the gypsum has dissolved into the soil (i.e., gypsum application in autumn, liming in winter).

Could gypsum become a compulsory additive for farmers in the future?

It is possible that the application of gypsum will become a part of the agri-environmental support system. It is highly unlikely that gypsum will become a compulsory additive financed by the farmers. One reason for this is that gypsum cannot be used on all fields.

How often should the gypsum application be repeated?

During the project, the fields will only be treated with gypsum once, in autumn 2016. If the autumn proves to be very rainy, some of the applications can be moved to spring 2017. The effect of the gypsum lasts between four and five years. After application, the effects of the gypsum will be monitored at least throughout the SAVE project, i.e., until the end of 2018.

Will the application of gypsum impact EU subsidies?

No. Even though the gypsum contains at most 0.2% phosphorus, this is not considered in the agri-environmental support system, as chemical compounds spread on the fields for phosphorus retention are excluded (Decree of the Ministry of Agriculture and Forestry regarding environmental support, 375/2015, section 3, Phosphorus fertilisers).

Why is there another study on gypsum application when this has been studied before?

Good results have been attained on the use of gypsum to reduce phosphorus pollution from agriculture in both previous studies and smaller-scale trials. In addition, this approach is estimated to be both more cost-effective and act faster than any other method of waterway protection currently in use. However, there are several questions and challenges relating to the widespread adoption of gypsum, of which more information is necessary before it can be recommended for broader use. A large-scale gypsum-spreading pilot will be carried out under the SAVE project to gain information on its usability on extensive catchment areas. The use of gypsum has never before been studied on such a large scale.

The extensive pilot of the SAVE project is intended to glean more information on practicalities, such as the availability of the gypsum and related logistics, the spreading of gypsum and how gypsum application will fit in with other agricultural work. In addition, further information is being sought on the impact of gypsum on the soil and on crop yield. The pilot area has a high clay content, but other types of soil are also present. The quality of the water is being monitored from river water in the river basin. In addition, the impact of sulphate on water organisms is being studied for the first time. The study will provide comprehensive information on the use of gypsum on different types of farms.