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Promising Research: Could Biochars Reduce Nutrient Loss Caused by Subsurface Drainage?

28. June 2022 | 5 min read

Biochars are carbon-rich materials made by heating biomass, such as wood chips, in a low-oxygen environment — the process is called pyrolysis. Due to their carbon-sequestering properties and potential co-benefits in agriculture, Biochars have lately received attention from the scientific community. Studies have shown that biochars can be used to improve soil nutrient and water availability while preventing nutrient leaching; however, more research is needed. Pipelife had a key role in initiating a novel type of multi-year biochar drainage experiment in Southern Estonia by supplying tailor-made wells for the project's setup.

A farmer working in a wheat field | Pipelife

Protecting Waterbodies While Maintaining Soil Fertility

While agricultural drainage systems are crucial for successful farming in many regions of Europe, a growing body of research shows that drainage runoff can contribute to water pollution. Draining excess water from fields often washes away soil nutrients that, in the long run, make lands less fertile while contributing to eutrophication and lower water quality of freshwater ecosystems.

A recent study carried out by Priit Tammeorg, Adjunct Professor at the Department of Agricultural Sciences of the University of Helsinki, explores if biochar filters could offer a solution to the issue. Dr. Tammeorg heads the  AgriChar research group, focusing on the effects of biochar systems on soil properties. Their previous research from long-term experiments in Helsinki shows that biochars, thanks to their microporous structure, may absorb and store soil nutrients such as nitrogen, preventing leaching. Furthermore, the application of certain biochars proves to increase soil fertility and improve yields while simultaneously sequestering carbon for centuries to come.

Adding biochar as backfill material around drainage systems | Pipelife
A layer of biochar is applied to a depth of around one meter | Pipelife

BIOCHAR AS BACKFILL MATERIAL FOR DRAINAGE SYSTEMS

AgriChar's current drainage study focuses on the long-term effects of biochar applications and is carried out in Viljandi county, southern Estonia. Researchers used biochar as backfill filter material around drainage systems and are researching how such a setup affects drainage water quality.

“Different biochars have been studied in field experiments over the world for the past 15 years, but in all such studies biochars are applied to the shallow topsoil layer, which is typically less than 30 centimeters. Our approach in this experiment is novel as we applied 5-centimeter layer of spruce biochar to a depth of around one meter. There, biochar is protected from wind erosion and forms a long-term carbon sink with potential benefits to leachate water quality. This is first such study worldwide, and we focus on the effects of the biochar filter on nitrogen, phosphorus, and carbon losses from the field,” explains Dr. Tammeorg.

To assess the efficiency of biochar filters, the study team needed tailor-made flow meter wells. Each well required a mid-wall with a V-notch on top to measure the real-time flow of water.

In close cooperation with the study team, Pipelife Estonia designed and welded eight customized metering wells for D800 drainage pipes. The wells were installed in fields in June 2021, and initially, the recordings were taken manually. Automatic data collection via water level recorders was added to the wells in May 2022, allowing for greater temporal resolution of the flow rates.

A Tailor-Made Solution for Research

Pipelife Estonia was selected as the supplier due to the efficient customer service and genuine commitment to finding the best technical solution for the uncanny project.

In developing the measurement wells' concept and drawings, Dr. Tammeorg worked closely with Pipelife's sales representative Kaspar Järve and Pipelife's technical specialists. The wells were designed and manufactured to fully meet the project requirements and ensure reliable functionality.

Dr. Tammeorg comments: "I would like to highlight Pipelife's flexibility in finding a solution and the speed of completing the order. Other companies in Estonia also perform custom welding, but Kaspar Järve from Pipelife clearly stood out by responding promptly and offering a solution that would be as efficient and cost-effective as possible. We would definitely choose Pipelife Estonia as a cooperation partner for the following projects and recommend them to others as well!"

Each well required a mid-wall with a V-notch on top to measure the real-time flow of water | Pipelife
A tailor-made flow meter well made by Pipelife Estonia | Pipelife

High-Quality Production for Reliable Performance

Well durability was another crucial requirement for the success of the project. As water expands when frozen, there was a risk of frost damaging the wells during the winter. Despite the study team's efforts to empty and plug the wells in autumn, the water table in the stream exceeded expectations and filled some of the wells anyway; therefore, they froze when the temperatures dropped. Two of the wells were even carried downstream and got stuck into a large-diameter concrete pipe while being under immense pressure from the floodwater trying to push through it. Nevertheless, all eight wells withstood the additional load and extraordinary weather conditions.

"When we lifted the wells out, we were very positively surprised by the strength of the welded joints. For example, we had an extreme situation when a well had to be lifted out by only one of the lifting handles while it was completely full of water and stones. These are incredibly strong wells," confirms Dr. Tammeorg.

Environmentally Friendly Farming Solutions

The field experiments continue, and the study results are expected to be published in a scientific article in 2024. The obtained data will provide valuable insight into how biochars can be used to prevent soil leaching, protect water bodies from agricultural pollution as well as will contribute to a wider knowledge of biochar systems helping to develop carbon-negative farming solutions.

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