Results emanating from the world’s longest cereal production trial has shown that long-term application of fertilisers can help boost soil carbon stocks, according to Rothamsted scientists.
These are the latest results from a trial that has been ongoing at Rothamsted since 1843.
The world-famous Broadbalk Classical Experiment has seen winter wheat grown in the one site continuously for the last 182 years.
The most recent soil analysis work at the site was carried out by an international team of scientists.
Soil carbon
It found that plots receiving nitrogen (N) and phosphorus (P) fertilisers contained up to 28% more soil organic carbon than those left unfertilised.
The study combined radiocarbon tracing, metagenomics, and metabolomics to offer new insights into how fertilisers influence the complex chemistry and microbial life that control carbon storage in soil.
Rothamsted’s Dr. Andrew Gregory said: “Soil organic carbon is critical for climate regulation sustainable food production and soil health.
“But its decline in many agricultural soils has been deeply concerning.
“Our findings show that long-term mineral fertilisation can actually enhance soil carbon sequestration, provided it’s managed carefully to minimise other unwanted impacts.”
Specifically, the Rothamsted research found that nitrogen and phosphorus acted in distinct ways.
Phosphorus alone boosted microbial activity and respiration. These are processes that release carbon, meaning that although microbial biomass increased, relatively little of it was converted into stable, long-lived forms of carbon.
Nitrogen fertilisation, by contrast, improved the efficiency with which microbes transformed plant material into more persistent “mineral-associated” carbon.
When applied together, N and P fertilisers produced the strongest effect – enhancing plant growth, promoting the conversion of short-lived “labile” carbon into more stable forms, and increasing both the quantity and durability of carbon stored in the soil.
Worldwide studies
Further analysis has found similar patterns elsewhere.
Across dozens of long-term fertilisation trials worldwide, N and P were associated with average soil carbon increases of 21% and 13%, respectively.
The benefits appeared to fade in the first decades of use, before strengthening again after about 30 years.
This suggests that soil carbon gains from fertilisation build slowly over time.
The findings, the authors of the Rothamsted research say, underscore the importance of long-term research and careful nutrient management in designing climate-friendly farming systems.
Work in Northern Ireland, carried out by scientists at the Agri-Food and Biosciences Institute (AFBI) has found that the long-term application of animal slurries to the same ground will build up soil carbon stocks.
This may well be another example of the aforementioned soil fertilisation effect.
