2023-06-22 09:34:00
The many peat areas in the Netherlands subside and emit a lot of greenhouse gases when they are drained for agriculture or livestock farming. Raising the water level and growing rice on the peat can offer a solution.
Julius Dullaert22 June 2023, 11:34
“This is our paddy field,” says Caroline de Roos. It is located in the middle of a polder in Oude Ade, a 19th-century village near Leiden. Behind her, the morning light falls on a small gully filled with water and plants. Eight neat rows of small risotto rice plants are bathed in golden light. In the distance, black and white cows graze and an old windmill stands once morest a dike. “Barefoot in the peat, the rice was planted by hand.”
The risotto rice is in the peat of the Vrouw Vennepolder to make a point: rice can be a valuable crop in the Dutch polder landscape. Leiden University has leased the piece of land from the Land van Ons citizen cooperative, which aims to increase biodiversity on agricultural land. Volunteers of the cooperation, such as De Roos, help maintain the rice field. According to the researchers, rice might be the solution to the peat soil problem in the Netherlands.
De Roos points to a dike, a few hundred meters past the rice. “We are going to dig a controlled hole there.” Behind the dike is the Boekhorstvaart, a ditch that flows into the Vennemeer further on. A small pipe with a diameter of fifteen centimeters in the dike can raise the water level of the polder – if this is not already done by the rain. A drainage pipe will be installed on the other side of the approximately 32-hectare field. In this way, the water level can be controlled while the exotic crops are being cultivated.
Peat problems
“I have seen old prints on which the land here was four meters higher,” says De Roos. She looks at the cityscape of Leiden that can just be distinguished in the distance. The Netherlands has a long history with peat soil. About one tenth of the Dutch surface consists of peat bogs. Much less than it used to be, but still enough to cause problems.
Peat consists of old plant remains that decompose very slowly due to the high water level in a peat area. There is little oxygen under water, so there are fewer fungi and bacteria that can break down the plants. If new plants continue to grow in the meantime, a thick layer of plant remains is formed. A layer of peat, sometimes thousands of years old.
Peatland in itself does not pose a major problem. But the Netherlands is a small and crowded country and a soggy layer of plant remains is not ideal for agriculture or housing. Peat areas are therefore often drained, since the Middle Ages. This makes the land usable once more. But at the expense of the environment.
Dried peat collapses. When the water is gone, the plant remains suddenly come into contact with oxygen once more. The soil shrinks due to the absence of moisture and oxidation takes place: now that there is oxygen once more, bacteria can suddenly quickly digest the plant remains. For example, the top layer of peat literally goes into the air and many greenhouse gases are released.
It is estimated that around 4 million tons of greenhouse gases are released into the air through the peatland every year. That is regarding 2 to 3 percent of total Dutch emissions. In addition to the climate consequences, the soil subsidence caused by the shrinking and oxidizing peat is also undesirable.
The peat soil subsides by an average of 8 millimeters per year, but there are also areas where this even happens with a few centimeters at a time per year, the Netherlands Environmental Assessment Agency saw. Soil subsidence causes a deterioration in the quality of water and nature, and can cause buildings or roads to subside. It should therefore be mandatory to reduce this decrease, says the Council for the Environment and Infrastructure (RLI), the government’s advisory body for sustainable development of the living environment. The decline should be halved by 2030. The water level should go up, not down.
Bet on one cow
Around the rice field in Oude Ade you hear and see many animals. Croaking frogs make De Roos stop a few times to listen. A hare runs past the risotto while the blackbirds sing and the cows moo ahead. “They are still young animals,” says De Roos. “Otherwise they are too heavy and sink into the ground too much.”
More than 80 percent of the Dutch peat soils are used as pasture for livestock. The water has been pumped away to allow grass to grow. “We are now betting not on one horse, but on one cow,” says Maarten Schrama (Leiden University), one of the researchers involved in the rice research. “In the Netherlands, the biggest problem in the peat meadow area is that we lack ideas regarding what is possible.”
Ten years ago, the scientist submitted research applications on the cultivation of food on peatland. However, the need was not recognized at the time, and the applications were rejected. Since that time a lot has changed. “The trick is to grow plants on peat to get where we want to be: cleaner water, less greenhouse gas emissions and no further degradation of the peat land,” says Schrama.
Rice appears to be a good candidate to achieve these goals. The plant can grow while the water level remains high. Peat soil does not have to be drained, there are no CO2 emissions or associated soil reduction, and food is also being grown in the meantime, which a farmer can sell once more. A beautiful picture – if the rice grows in the Netherlands and does not emit too much methane.
Polderrisotto
It is colder in the Netherlands than in traditional rice countries. The type of risotto rice that is now grown in the South Holland peat polder was chosen following a test in a valley in Switzerland, where the climate is comparable to that in the Netherlands. The risotto proves to be resistant to cold. “The researcher of the project in Switzerland told us that we can write rice cultivation here on our stomach if this species does not do well in the Netherlands,” says Schrama with a laugh.
The greatest danger for Dutch polder rice is the wet weather. Schrama: “If it keeps raining and the plant doesn’t get the chance to dry, mold will develop.” Furthermore, the Netherlands has a shorter summer compared to the country where the plants come from, so that the rice gets fewer hours of sunshine. An advantage of the Dutch summer is that the days are longer than in the south. This in turn provides more light for the crops.
The small strip of rice, regarding the size of a ditch crossing a small meadow, should yield regarding 75 kilos of rice in the autumn. In addition to the harvest yield, the plant’s emissions are also the subject of research. It must be checked whether the plant emits a lot of methane, a strong greenhouse gas. Only when both points are clear will it become clear whether the project is a success.
Rice cultivation on Dutch peat soil. Image Rosalie van der Does
The Leiden researchers are not the first to experiment with rice in peatland. “We have shown that growing rice on Frisian peat soil is possible,” says Dirk Osinga, who in 2021, as a lecturer at Aeres University of Applied Sciences, also tried to grow various crops in the peat together with his students.
Their rice plants, a northern Chinese variety, grew ‘surprisingly well’. The harvest was only quite small. Further research, for example with other varieties, is therefore still necessary.
Insulation material
Other useful plants that did well in Friesland were cranberries and bulrush, a type of reed whose spikes look like brown, fuzzy cigars. “Bulrush can be processed into insulation material,” says Osinga. Leiden researcher Schrama also thinks cattail is a useful plant that grows well on peat soil. He and his team, on the other hand, focus specifically on food crops, because there is still little attention for this and they think they fit better in the Netherlands.
“For fiber crops such as bulrush, you immediately need hundreds or thousands of hectares of land to be able to produce enough for the insulation companies. In the Randstad there are all small pieces of land. These are more suitable for high-quality food cultivation,” says Schrama.
That is why experiments are also being carried out with other food crops in the Vrouw Vennepolder. There are fruit trees familiar to the Netherlands, such as apple trees. But also foreign plants, such as pecan and almond trees can be seen on both sides of the risotto field.
About a hundred meters away from this colorful collection of plants, another test field has been created. Here are cranberry bushes, also known as the cranberry. The plants with thin stems and small dark green leaves bear small, white-pink flowers. De Roos inspects them.
“Veenland is as acidic as cola, many plants cannot grow there,” says Schrama. Cranberries, on the other hand, do well in acidic, wet soil. The water level is slightly lower than with rice plants, which are literally in the water. For cranberries, the level should be regarding five centimeters below the ground.
New revenue models
Each crop that grows in the peat comes with its own advantages and disadvantages. But the idea is regarding the same with every plant. “Crops of this kind in a high water level can fend for themselves and fit into a dairy farmer’s business operations,” explains Schrama. “You have to harvest cranberries in November, for example. This is exactly when dairy farmers don’t have a lot of work.”
The scientist thinks that organic food cultivation in peatlands can be a profitable and environmentally friendly alternative to livestock farming. “The fact that we have grown the same thing for ten centuries in a very stable climate does not mean that we cannot do anything else. Growing organic rice from Dutch soil, that is of course fantastic.”
Read also:
Wet grass reduces greenhouse gases in the air
Peat meadows that are kept wet from the soil release much less CO2 than meadows that are ground dry. This has emerged from five years of experimentation in North Holland. ‘Ultimately we will even have to capture CO2 in the peat meadows once more with wet crops.’
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