Milk production on heavy soils and the Border/Midlands/Western region
Why is this research important?
As a European Union (EU) member state, Ireland has developed a national Climate Action Plan that includes targets to reduce greenhouse gas (GHG) emissions from agriculture by 25% by 2030. Foremost among the farm management practice changes required, a 25% reduction in national chemical nitrogen (N) fertiliser application will be required within Irish agriculture by 2030.
In pasture-based production systems which are typical to Ireland, maintaining farm productivity and profitability while reducing chemical N use levels is hugely challenging and requires the successful incorporation of legumes within grazed pastures. The ability to generate a substantial legume component (20-25%) such as white clover (WC) within perennial ryegrass (PRG) dominated swards is critical to replace chemical N fertiliser with biologically fixed N and maintain pasture productivity.
While there is an abundance of prior research that has clearly established the fertiliser replacement capacity of WC, some more recent studies have also observed increased milk and fat plus protein yields from PRG-WC swards when compared with PRG-only swards. Despite these many advantages, there has been limited incorporation of WC within commercial grazing pastures in Ireland with extremely low rates of pasture renewal reported (1-2% annually).
The majority of the research undertaken to date on WC incorporation in Ireland has been conducted on freely draining loam soils with long grazing seasons and advantageous climatic conditions with minimal evaluation within poorly drained soils that experience shorter growing seasons due to adverse weather conditions. Such unfavourable conditions result in reduced pasture production and utilisation and may also hinder WC establishment due to extended periods of low soil temperatures and soil moisture saturation. Moreover, there has also been limited research on the transition from PRG-only to PRG-WC systems as most studies focus on the pasture production from entirely newly established swards.
What the research tells us
This study, undertaken in Ballyhaise Agricultural College, investigated the transition from old PRG swards to newly established PRG and PRG-WC swards on a wetland grazing dairy system in the Border/Midlands/Western (BMW) region of Ireland. The sites poorly draining soils and steeply sloped drumlins provided a unique opportunity to evaluate the potential contribution of newly established PRG and PRG-WC swards within a whole farm system multi-year evaluation.
The results of the study are of particular relevance to the establishment of WC within livestock grazing systems on more marginal land types such as those in the BMW regions of Ireland. The accelerated transition to PRG-WC undertaken herein is indicative of the likely longer-term impacts for commercial grazing farms within a more prolonged timeframe. Moreover, the novelty of reporting on the immediate transitional phase impacts from old to rejuvenated pastures with/without WC has not, to our knowledge, previously been reported within the published literature.
Research at Ballyhaise College
The primary objective of the research undertaken at Ballyhaise Agricultural College is to investigate the transition from PRG swards supported with high rates of chemical N application to a low chemical N PRG-WC dairy system on a wetland soil type in the BMW region of Ireland. The two sward types compared are a PRG-only or PRG-WC farmlets receiving an annual application of 250 or 125 kg N/ha, respectively. In 2021 and 2022, 30% and 20%, respectively of each grazing platform were reseeded with 3 high Pasture Profit Index PRG varieties with or without WC. Following establishment, PRG-WC swards received no application of chemical N post-sowing once WC composition within the sward exceeded 20% on a DM basis. All treatments are managed similarly at grazing in terms of pre-grazing pasture mass, post-grazing sward height, and residency time.
PRG swards receive chemical N fertiliser at each rotation post-grazing from February 15th to September 14th each year whereas PRG-WC swards receive the same rates of chemical N as PRG for the first 2 applications until mid-April, and thereafter receive reduced rates of N application depending on sward WC content during the remainder of the year.
Where sward clover contents exceeded 15% from early May, no additional chemical N is applied from May onwards. In contrast, where clover contents of 0-5 or 5-15% are recorded in early May, chemical N application is reduced by 0 or 50% of PRG application rates respectively, for the remainder of the year. All swards receive 30 kg/ha of chemical P and 60 kg chemical K during establishment, and a further subsequent application of K (45 kg/ha) during autumn each year. Slurry is evenly distributed to all treatments by block where possible during the grazing season.
OutputS
Links to papers
- Grazing season length and stocking rate affect milk production and supplementary feed requirements of spring-calving dairy cows on marginal soils
- Effect of stocking rate on milk and pasture productivity and supplementary feed use for spring calving pasture fed dairy systems
- Pasture-based dairy systems in temperate lowlands: challenges and opportunities for the future
Contacts
Ballyhaise Farm: Evaluation of Low Nitrogen Dairy production systems: Donal Patton (donal.patton@teagasc.ie)