Analysing the farm-level impact of multispecies swards on Irish ruminant production systems
Irish traditional pasture-based ruminant production is facing many challenges: agriculture is the largest contributor to Irish greenhouse gas emissions; profitability at farm level in beef and sheep farms is low and productivity of conventional permanent pastures is compromised.
Reseeding permanent pastures is a way of addressing the productivity issue with the aim of increasing farm profit, with farmers largely turning to monocultures of perennial ryegrass. These swards have high yields, but are quite dependent on nitrogen inputs, increasing production costs and greenhouse gas emissions. Research has shown that multispecies swards have higher yields than monocultures, at lower fertilization rates, and can also reduce lamb’s days to slaughter and thus, greenhouse gas emissions (per kilogram of meat).
However, whole farm-level analysis of the benefits and drawbacks of multispecies is still lacking. In this project we aimed to explore the impact of reseeding with multispecies, versus perennial ryegrass, on two contrasting farm objectives: reducing greenhouse gas emission and increasing operating profit. Using the bio-economic model FarmDESIGN and based on data from Devenish experimental farm at Lands of Dowth, we built three mixed grazing farms (i.e., a traditional permanent pasture farm, a perennial ryegrass farm, and a six-species multispecies farm).
Methods & Results
We started with a traditional PP farm and calculated its optimized stocking density (LU), GHG emissions and operating profit (OP). Secondly in this modelling exercise, we simulated the reseed of the whole farm in one year (one with PRG and one with 6MS). This generated a significant drop in the farm’s operating profit during that first year, even with the higher yields obtained with both PRG and 6MS, but we then focused on the OP from the second year (considering animal replacement and fixed costs, but not cultivation costs). Whole farm GHG emissions were also higher than in the original PP farm for both reseeded options. However, when considering GHG emissions per LU, we saw an increase in the PRG and a decrease in the 6MS (see Table 1 - below)
Table 1 Comparison of results obtained in the original PP farm and the reseeded PRG and 6MS farms.
GHG and OP in the PRG and 6MS are expressed as the percentage relatively to the PP farm. The OP is that of the second year of farming (not the swards and herd establishment year), considering no cultivation costs and just animal replacement costs.
With the preliminary results of this basic modelling exercise, we can clearly see the potential of MS, especially how they can outperform PRG. However, there were several issues that were not considered at this stage. For instance, reseeding the whole farm would be a great investment that most farmers cannot afford all at once, one way of doing it is by dividing the farm in fractions corresponding to the years the reseeded pasture should last. PRG pastures should last up to 10 years, then each year you can reseed 1/10 of the farm. One of the drawbacks of MS is that their persistence is lower than PRG, with the herbs almost disappearing in less than 5 years. However, over-sowing specific species is possible and something to consider when evaluating MS persistence and sowing costs). It is clear that further research is needed to develop blueprint for the correct management and incorporation of MS and present them as a feasible option for the average Irish beef and sheep farm, however, under research conditions, they are showing quite promising results.