Dyfi Dairy - Full Report
The following report has been prepared by Sam Wren-Lewis and Sophia Morgan-Swinhoe.
Background
Having recently moved our dairy herd onto a 117-acre hill farm near Machynlleth, we’re keen to adapt and integrate new methods of management for the long-term benefit of the soil and environment. The farm consists mostly of perennial ryegrass which has previously been dependent on nitrogen fertiliser. As the cost of nitrogen fertiliser is increasing, and there’s evidence to suggest that relying on fertiliser use is detrimental to long-term soil health, farmers are increasingly looking at ways to cut out fertiliser use whilst promoting soil health and biodiversity on their farm. Establishing herbal leys has been identified as an important way of both fixing nitrogen and improving soil health.
We’re interested in the opportunity presented by direct drilled, herbal leys as a way of maintaining productive yields alongside delivering a number of additional benefits, such as increasing soil health, livestock health, nutritious forage, carbon sequestration, soil water retention, drought resistance, and biodiversity. These additional benefits align the proposed project with the Wales Sustainable Farming Scheme (SFS) and its Sustainable Land Management objectives and outcomes.
Although there’s good evidence of the productivity and environmental benefits provided by herbal leys - such as those outlined by the EU funded Toolbox of Multi-Species Swards (TOMS) project - there is less evidence on the effectiveness of herbal leys on: a) regenerating perennial ryegrass pasture previously dependent on nitrogen fertiliser, and b) direct drilling as a minimal-soil-disturbance method of establishing herbal leys. We wish to investigate both of these opportunities within the context of Welsh upland dairy farming.
Purpose of the work: aims/objectives
The project aimed to investigate the effectiveness of replacing nitrogen fertiliser use with direct drilled herbal leys to regenerate perennial ryegrass pasture, while maintaining productive yields. We established four trial plots: three different herbal ley mixes direct drilled into perennial ryegrass pasture, and one pure perennial ryegrass pasture as a control.
The trial plots were designed with the following properties:
Cae Mawr - legume and herb rich sward: This plot was used for grazing dairy cows, with a focus on nitrogen-fixing and deep-rooting plants.
Cae Ffordd - meadow hay ley + diversity: This plot was used for hay/haylage, with a focus on herbs, wildflowers, and multiple grass species.
Cae Dan Helm - anthelmintic/goat health grazing: This was used for grazing goats, with a focus on plants with anthelmintic properties.
We measured a number of outcomes before and after establishing the herbal leys to
determine their effectiveness. In particular, we measured: a) soil structure, b) soil pH, and c) soil organic matter (SOM %). We aim to share the results of the trial with other farmers in similar contexts and will use the findings ourselves to inform future activities on our farm.
What we did: methodology
- Identifying Trial Plots (Autumn 2023). We identified four one-hectare plots for establishing three different herbal ley mixes direct drilled into perennial ryegrass pasture (see below), and one pure perennial ryegrass pasture as a control. We made sure there were no significant differences between the plots e.g. in soil types, grass species, topography, etc. and recorded any notable differences that could act as confounding factors.
- Determine Herbal Ley Mixes (Autumn 2023). We consulted with an advisor from Cotswolds Seeds to determine three different kinds of herbal ley mixes to be direct drilled into perennial ryegrass pasture: 1) A legume and herb rich mix used for grazing dairy cows, with a focus on nitrogen-fixing and deep-rooting plants; 2) A meadow hay ley and diversity mix used for hay/haylage, with a focus on herbs, wildflowers, and multiple grass species; 3) An anthelmintic/goat health grazing mix used for grazing goats, with a focus on plants with anthelmintic properties.
- Before Measures (Autumn 2023). Before establishing the herbal ley mixes, we measured the trial plots for soil structure (VESS - Visual Evaluation of Soil Structure - and a worm count), soil pH and soil organic matter. Alongside observations of yield productivity, these measures were taken again at the end of the trial to investigate the effectiveness of the different herbal ley mixes in comparison to the control. We made sure to geotag the field locations of the soil samples using so that soil samples can be taken from the same field locations at the end of the trial.
- Establish Herbal Leys via Direct Drilling (Spring 2024). For each plot, we made sure the existing sward was grazed or cut as tightly as possible before sowing so that it didn’t out compete the new seedlings. We also made sure the ground was warm but not too dry, and that the seeds were shallow drilled, using a specialist grass seed drill (in comparison to a cereal seed drill, which may drill too deeply). After direct drilling the different herbal ley mixes in our field plots, our livestock grazed the existing sward, but were removed after 4-5 days to prevent damage to the new seedlings. We reintroduced them for a light graze after 6-8 weeks to knock back the existing sward, again taking care not to damage seedlings.
- After Measures (Autumn 2024). At the end of the growing season, we re-measured the trial plots for soil structure, pH and organic matter, 12 months after the Before Measures were taken at the beginning of the project.
- Results and Evaluation (Winter 2024). Using the results from the trial, we evaluated the impact of the different herbal ley mixes on yield productivity, soil health, and other anticipated environmental and animal health benefits.
Outcomes: results
VESS (Visual Evaluation of Soil Structure)
Worm count
Compaction
There was no significant change in VESS, worm count, and compaction over the course of the trial. However, this is to be expected within the short time period of the trial.
Soil pH
In all four plots, pre-treatment, the pH was at below optimum levels - between 5.5-5.99. We wanted to investigate whether sowing herbal leys would increase the pH without the need for applying lime to the soil. We received mixed results. Although the pH did increase in two of the plots (Plots 1 and 3), the pH decreased in one plot (Plot 2 - Cae Ffordd) to under 5.5.
We witnessed a similar decrease in the Control plot, which suggests the decrease is due to continued usage of non-biodiverse grassland for grazing. It may be that the sowing of herbal leys in Plots 1 and 3 helped reverse this trend.
Soil Organic Matter (SOM)
Organic matter % was high across all four plots, both pre- and post-treatment. The most significant change over the course of the trial was in Plot 2 (Cae Ffordd), which increased from 9.17% to 10.9%. However, it’s unlikely that the herbal leys would’ve caused significant changes in SOM over the short time period of the trial.
Evaluation
In general, the success of the trial was hampered by weather and logistical factors. Unusually wet weather in April and May meant that the herbal ley mixes weren’t direct drilled until June. Although the pasture was topped and tightly grazed before direct drilling, the ryegrass pasture still largely outcompeted the herbal ley mixes.
If we were to repeat the trial, we would ideally direct drill the herbal ley mixes in early April. Alternatively, if the weather window for sowing ended up being later, we would either plough and/or harrow the fields before drilling.
Nonetheless, we did manage to establish the herbal ley mixes in all three plots and expect to see further establishment in subsequent years (due to the seeds in the soil seed bank being disturbed by mob grazing). We also expect that the established herbal leys have already provided benefits to the soil, pasture, and animal health. For instance, over the course of the trial, incidents of worm burden in the goat herd halved in comparison to previous years.
In the short timescale of the trial (one growing season), it’s too early to see significant benefits in terms of soil health and pasture growth. However, this is something we expect to observe in subsequent years and there are already signs of some improvement. Organic matter improved in one plot (Plot 2) while staying roughly the same in the control plot. In the other two plots (Plots 1 and 3), pH improved while slightly declining in the control plot.
In future trials, due to the poor pH of the soil, we may consider applying lime before sowing the herbal leys to see if that has a significant impact on their establishment. We may also consider applying a mycorrhizal inocula to improve the biology of the soil.