26 January 2021

2 minute read

Europe

With this knowledge, dairy farmers can see how great the effect of carbon sequestration in the soil is on their carbon footprint.

By increasing the organic matter content in the soil, farmers can capture carbon on their land and thus reduce the dairy farm's carbon footprint. Organic matter consists of about half carbon. To determine how much carbon has been captured in the soil (soil C), it must be measured.

Difficult to measure

“But it is very difficult to accurately measure soil C,” explains Jan Peter Lesschen of WUR. “In this way, a stock of 50 to 100 tons of carbon per hectare is stored in the top soil layer. This is not necessarily evenly spread over the plot. Currently, a dairy farmer takes a sample per parcel once every four years. A carbon sequestration of 0.5 tons is then only a very small change in this stock (0.5 to 1%), which is also often less than the accuracy with which the soil is analyzed. In addition, geographical and weather factors also influence the amount of stored carbon, such as small height differences, the presence of peat layers and the effect of temperature and moisture. ”

Monitoring system

An alternative is to calculate soil C on the basis of scientific models. But here too, the uncertainties per farm are still great, for example because it is difficult to estimate how much carbon from crop residues remains on the grassland.

Lesschen and colleagues from Wageningen Environmental Research and Wageningen Livestock Research have developed a monitoring system that is accurate enough to give a reliable result over larger numbers of plots from multiple companies. At the 33 participating companies, current practice contributes on average to a reduction of the carbon footprint of 2%, without actively controlling soil carbon sequestration. The researchers propose to sharpen the models with more measurements from the field over several years, in combination with annual soil samples.

Refine scientific model

Lesschen: “We want to measure soil C frequently on a large number of plots. In addition, activities such as fertilizing, grassland renewal and crop rotation on those plots must be collected centrally. When more measurement data becomes available over time, we can fine-tune the scientific model and thus make more accurate calculations suitable for individual plots. ”

In the meantime, dairy farming can focus on taking measures that are already proven to help capture carbon, such as minimizing grassland renewal and maximizing the supply of carbon from manure and crop residues.