CASE STUDY

Biochar in Grassland and Arable Systems: Year 2 Findings from Field Trials

At Black Bull Biochar, we’ve successfully completed the second year of our field trials, assessing the performance of our tailored biochar across both grassland and arable plots.  

Biochar is a carbon-rich material produced by heating biomass in a low oxygen environment, resulting in a stable form of carbon. Throughout the trial, we used our own tailored PinChar product. While biochar has a range of potential uses, Pinchar is designed to enhance soil health, improve crop productivity, and increase nutrient retention. We specifically developed and tested this product in agricultural systems to maximise its effectiveness on farms.   

These trials, carried out in collaboration with the UK Centre for Ecology & Hydrology (UKCEH) and Scotland’s Rural College (SRUC), were set up to evaluate how our biochar performs when co-applied with organic fertilisers in arable and grassland systems. Low application rates of under 1 tonne per hectare were used as we investigated the effects of biochar use on crop yield and soil properties.   

This marked the second year of biochar treatment and field analysis. Encouragingly, we observed continued improvements even on plots that did not receive a second application of biochar, indicating that PinChar’s effects persist beyond a single season.   

Key improvements were observed in the grassland plots — notably an 18% increase in yield, alongside measurable gains in soil organic carbon and pH. Similarly, arable plots showed strong results, with a pronounced increase in yield, which rose on average by 30% compared to untreated plots.

PLOT KEY RESULTS

Grassland

Increase in annual grassland yield

Greater available soil nitrogen on average

Increase of available nitrogen in slurry

Increase in soil pH

Grassland plots key results

PLOT KEY RESULTS

Arable

Measured whole crop yield increase

Up to

Greater available soil nitrogen on average

Increase in soil organic carbon

Increase in soil pH

Arable plots key results

The summary of results above were drawn from work at SRUC’s research farm in Crichton, where we established 20 trial plots, split evenly between grassland and arable, with untreated controls to enable direct comparison.

Trial Methodology

Preparing the biochar and organic fertiliser

Grassland

Before land application, the Slurry-PinChar mix was prepared and stored for six weeks, to allow nutrients time to bind to the biochar’s surface. PinChar was added at 1% by dry weight. Both slurry types were sampled before and after biochar addition, enabling comparative analysis between the control and treated mixtures, as well as an assessment of any nutrient increases. (See ‘Slurry Analysis’ results below.)

Arable

Before land application, PinChar was added to the farmyard manure (FYM) at a rate of 10% by dry weight. The FYM-PinChar mix was then turned and left to sit for approximately one month, allowing for microbial activity and nutrient interaction to develop during storage. This preparation period helped condition the mix prior to field application, supporting improved nutrient retention and soil impact.

Applying to the fields

PinChar was applied to the crops as a fertiliser additive, using methods tailored to either arable or grassland soils.

Grassland

On grassland plots, as described above, PinChar was mixed into slurry at a 100:1 ratio and applied after a conditioning period.

Both the treated and control slurries were applied using precision slurry equipment fitted with a dribble bar. Additional slurry applications, without biochar, followed in June and July each year.

Harvest and sampling

Crop biomass was harvested separately from each plot using a precision harvester to allow accurate comparison across treatments.. The biomass was then dried to determine dry matter (DM) yield, which was used to calculate the final yield per hectare (DM t/ha).

Grassland

Grassland plots were harvested three times per year, reflecting normal management practices. Cuts were conducted during May, July and September.

Arable

Arable yield was assessed by measuring whole crop yield, with harvesting completed in August.

Soil and crop samples were collected at multiple points during the trials to capture both immediate and longer-term effects. Sampling was carried out on both treated and control plots under grassland and arable management.
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Results

Results from the Biochar+ plots did not show statistically significant differences compared to plots that received a single application of biochar. For this reason, averages in this report reflect all biochar-treated plots combined.

This reinforces the strength of the response seen from a single application of Pinchar, even without reapplication in the second year.

Slurry Analysis

Analysis of the slurry showed that adding 10 kg of PinChar per tonne significantly improved nutrient retention. Plant-available nitrogen increased by 30%, ammonium by 59%, and total organic carbon by 43% compared to untreated slurry, indicating enhanced preservation of both nutrients and organic matter.

These gains were greater than expected from the biochar’s own carbon and nutrient content, suggesting that PinChar may help preserve existing organic matter in the slurry by slowing its breakdown during storage.

Soil and Crop Responses

Yield

One of the clearest indicators of biochar’s impact was the difference in yield between treated and control plots.

The results show significant increases to grassland yields with low-dose biochar applications. Second cut silage yield from the PinChar plots was 43% greater compared to the plots with only slurry, and annual results showed a significant yield increase of 18%. Arable plots showed an even greater response, with final cut yield increasing by 30%.

This significant improvement is likely the result of synergies in the interactions between the plant, biochar and the soil, including: - Enriched soil microbial and fungal communities - Increased adsorption and exchange of ammonium - Enhanced root development - Improved soil structure, water properties, and aerobicity.

Importantly, this increase in yield did not cause a drop in silage quality, with crude protein, ash and modified acid detergent fibre staying the same across silage from the biochar and non-biochar plots.

Soil pH

An interesting outcome from this year’s trials was the effect of biochar on soil pH. There was a measured increase of 0.49 in grassland plots and 0.22 in arable plots by the end of the trial period.  Soil pH is a key driver of nutrient availability, and this observed liming effect suggests improved potential for nutrient uptake in both systems.After the second year of biochar field trials, we were able to gather detailed data on the effect of PinChar across both arable and grassland systems. These findings demonstrate PinChar’s effectiveness in improving soil and crop performance, and the results provide strong evidence that biochar drives measurable gains in sustainable and regenerative farming.

While pH increases were also observed in some control plots, biochar-treated soils consistently showed higher values, particularly in the grassland plots. In the arable system, biochar also appeared to buffer against short-term pH decline, helping maintain more stable conditions over time.

Soil Nitrogen

Biochar co-applied with organic fertiliser improved soil nitrogen levels, with increases of 19% in grassland plots and 17% in arable. These gains were linked to higher concentrations of nitrates and ammonium, suggesting that biochar helps retain plant-available nitrogen in the soil. This effect is likely due to biochar’s capacity to hold ammonium and reduce nitrogen losses through leaching and volatilisation, helping to sustain a more consistent nitrogen supply over the growing season.

The combination of improved retention and nutrient slow-release points to biochar’s potential to increase fertiliser efficiency and support sustained crop growth over time.

Biochar contains a highly stable form of carbon, particularly when produced at high temperatures, with a mean residence time in soil spanning decades to centuries. This makes it a long term carbon sink.

CONCLUSION

Paving the Way for Biochar in the UK

After the second year of biochar field trials, we were able to gather detailed data on the effect of PinChar across both arable and grassland systems. These findings demonstrate PinChar’s effectiveness in improving soil and crop performance, and the results provide strong evidence that biochar drives measurable gains in sustainable and regenerative farming.

The trials showed that a single application of biochar can lead to lasting improvements in soil health, fertiliser efficiency, and manure nutrient value.

After such breakthrough trials Black Bull Biochar now has a limited stock available for purchase in 2025. We are continuing to work with farmers across the UK to integrate biochar into practical nutrient management plans, unlock long-term soil improvements, and scale up productive and resilient agriculture.