Transitioning to low chemical N input clover swards at Ballyhaise

In advance of this week’s Ballyhaise Open Day, taking place on Wednesday, July 24 from 10am, the project team summarise the current trial on clover grazing systems, share early results and look at the implications this research may hold.

The financial landscape for dairy production has been transformed during the last three years with unprecedented increases in both dairy product prices and costs at farm level.

High productivity pastures, however, remain the cornerstone of efficient grazing systems, contributing to more than 80% of the feed requirements on dairy farms.

It is hugely challenging to maintain farm productivity and profitability while reducing chemical nitrogen (N) use levels. It requires the successful incorporation of a substantial legume component within grazed pastures.

Although the incorporation of white clover (WC) within perennial ryegrass (PR) grazing pastures has been proven to reduce requirements for chemical N fertiliser in numerous research studies, its impacts have mainly been evaluated within free draining soil types.  

Can we adjust the system on a heavy soil type to reduce reliance on supplementary feed imports, incorporate clovers within grazing swards and refine of day-to-day operations to reduce nutrient losses? The current five-year study in Ballyhaise aims to address these questions.

Current Ballyhaise experiment

The current experiment is a five-year systems trial focused on the transition from old PR only swards to new PR and PR-WC swards through the combined process of full reseeding and oversowing.

The experiment consists of two sward types: PR only swards which receive 250kg chemical N per hectare per annum; and newly established WC (WC-new) or oversown WC (WC-over) swards, which receive 125kg N per hectare per annum.

Details of establishment and management will be discussed at the Ballyhaise’24 – Dairy Open Day. Further information on this event is available here.

Results to-date

During the study, 11 grazing rotations were achieved during both 2021 and 2022, with 10 rotations during 2023. The total number of days during which cows grazed varied each year and between sward treatments (259 days for both PR and WC in 2021, 257 and 256 days for PR and WC in 2022, and 243 and 235 days for PR and WC in 2023, respectfully). The effect of sward type on turn out and housing during the study period is outlined in Table 1 below.

Table 1. Dates of turnout of calved cows in spring and housing for the winter, additional days housed during the main grazing season (to avoid excessive damage to the sward)

The transition from PR-old to newly established and oversown pasture had no significant impact on grazing characteristics. Total pasture production was significantly reduced during the year of new sward establishment from 14,182 kg DM/ha in PR-old to 8,925, 8,561 and 11,830 kg DM/ha in newly established PR-new, WC-new and WC-over swards.

The significant reduction in pasture yield in newly established swards is attributed to extended closed periods between spray off of the old swards and first grazing of the new sward, which is mainly due to inclement weather during establishment.

In the years subsequent to establishment, total pasture production was increased for new PR and WC swards (14,891, 15,642 and 15,218 kg DM/ha in PR-new, WC-new and WC-over, respectively) when compared to old permanent pasture.

The WC-new and to a lesser extent WC-over swards delivered a reduction in mean chemical N fertiliser application from 229 and 230 kg N/ha for PR-old and PR-new to 119 and 90 kg N/ha for WC-over and WC-new (Table 2).

Table 2. The effect of sward change (SC) transition from old permanent pasture (PR-old) to newly established swards (Perennial ryegrass (PR-new) and Perennial ryegrass white clover (WC-new)) and clover oversown (WC-over) swards on total pasture production and chemical fertiliser application during the three-year transition period

Animal performance

Transitioning to WC systems resulted in modest increases in both milk yield (5,197 and 5,092 kg) and milk fat plus protein yield (473 and 461 kg/cow) for WC swards when compared to PR only swards while there were no significant differences observed for milk composition (fat, protein and lactose) between the two sward types during the transition. Similarly, body weight and body condition score were comparable for both sward types.

Implications of this research

1. Previous studies have stated that a minimum WC sward content of 20% was required to achieve the production benefits of WC in grazing swards. However, the overall sward WC contributions in this study only reached that threshold level in the third year of this study when a significant increase in milk production was achieved.
2. Nonetheless, even at relatively lower sward WC contents during the transition period, WC can make a positive impact primarily in terms of maintaining herbage production while reducing requirements for chemical N fertiliser application. This change can help to insulate farmers from dramatic price fluxes in both milk prices and fertiliser costs which have occurred in recent years.
3. In addition to the substantial economic advantage, the development of such systems will reduce greenhouse gas emissions associated with the pasture-based grazing systems under evaluation therefore further improving the sustainability of Irish grazing systems.

The team behind the systems study in Ballyhaise are: Helena Walsh, Donal Patton, JohnJoe Collins, Karina Pierce and Brendan Horan.

More info on the Ballyhaise Open Day

In the below video, Brendan Horan, Helena Walsh and John Joe Collins provide an overview as to what will be discussed on the day:

More information on the Ballyhaise’24 – Dairy Open Day is available here.