Posts Agriculture, Circular economy, Environment, Forestry

While carbon content of agricultural soils is declining, Luke’s researchers are now trying to find answers to how carbon can be sequestered back, permanently. When organic side streams from forest industries are used as soil amendment in fields, crops are healthier and watercourses are cleaner. It is all down to microbes.

When special scientist Kimmo Rasa noticed that fibre-rich side streams from forest industries clearly reduced nutrient leaching and erosion in farmland, it was time to call Taina Pennanen, researcher of soil microbiology, and her colleagues to the test field and dig deeper into life under the surface of fields. It was found that fibres also changed the microbial composition of agricultural land in a positive direction.

“Soil improvement fibres have been used in fields for long, but only experience-based knowledge of their impact on agricultural water protection has been available. Compared with inorganic soil improvement material, fibres potentially accelerate microbial activities”, Rasa says.

Next autumn, nutrient-rich fibres will be spread over 80 hectares in the catchment area of lake Tuusulanjärvi in southern Finland. The test is part of KUITU (FIBRE) research project and aims to identify whether fibres can also affect nutrient loads from agriculture on a large scale.

“Traditionally, mineral-based fertilizers have been spread on fields. There have also been attempts to increase microbial biomass, but added microbes cannot survive for long in fields. Recent research results show that microbes will find their way to fields, as long as there is something where they can grow”, Pennanen says.

Microbes can help keep crop diseases away

Rasa’s study started from a need to find new uses for pulp and paper industry organic side streams that have previously been burned at a low efficiency rate. In soil, fibres offer the carbon-rich substrate microbes need. Next, researchers will study how microbes in agricultural land can help to improve the carbon balance and even mitigate climate change.

It has already been known since the 1940’s that the aggregate structure improves when microbes adhere to soil minerals. Next, it will be studied whether soil could permanently sequester carbon by means of microbes. According to current knowledge, more than half of soil carbon comprises dead microbial biomass. Living microbes sequester carbon and react with minerals. As a result, they generate carbon, which does not directly dissolve from soil.

Pennanen is now eagerly waiting to receive microbial analyses from 600 Finnish fields later this year.

“Then, we will hopefully know more what microbial groups are needed in mineral aggregation and carbon sequestering”, Pennanen says.

In addition to soil improvement fibres, Luke is studying the impact of crushed bark on the health of field crops. The idea came from a US study, in which a serious Fusarium- problem was taken under control using plant litter from forests.

“Bark is a strong material, as it protects trees for up to 150 years. It contains a broad range of chemicals to study”, Pennanen says.

“Side streams do not offer any precise cure for diseases but, if a field has a good structure and microbes, it will be more difficult for diseases to hit crops”, Rasa adds.

“What makes forest land different from farmland is that fields do not contain roots of long-lasting plants or their mycelia, in particular. If the biological life cycle of microbes remained in fields, fertility and plant cover would improve and leaching would decrease”, Pennanen says in summary.

New knowledge about biodiversity and sustainable farming practices

Research of soil organisms is growing fast in Europe. Luke is a member of SoildiverAgro, a joint project of nine countries. Its aim is to collect knowledge about biodiversity in agricultural soil and sustainable farming practices. Mouldboard ploughing may be detrimental to soil organisms, and now, new research data about minimum tillage methods and direct seeding can be obtained through field experiments. Benefits of side streams of the forest industry are also studied in potato fields. Senior scientist Krista Peltoniemi leads international research at Luke.

Let’s return to soil improvement fibres from forest industries. Should all farmers spread them on their fields? Do they only produce benefits or do they consume nitrogen from fields?

Rasa says that some harvest losses have been found when using cellulose fibres alone, but only during the first year of use. Furthermore, no harvest losses have been found when using nutrient-rich fibres. Fibres contain heavy metals accumulated during tree growth, but if they are used in accordance with regulations, no problems should be expected.

Researchers therefore agree that the answer is yes, fibres should be used in fields. Good microbes help make production more sustainable.

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