Smart farming
Helen Sheridan
nutrients from different levels of the soil profile rather than being restricted to a particular level.
This diversity in root types may also have beneficial implications for soil structure, carbon sequestration and fertility.
Similarly, if the mixture contains individual species that yield across different times during the growing season, then they can complement each other and potentially increase overall yield.
Facilitation on the other hand, refers to the ability of some species to facilitate the growth of other species.
For example, legumes such as red and white clover have the ability to fix atmospheric nitrogen and make this available for plant growth. Therefore they have the potential to facilitate plant growth and production through this process, even in the absence of nitrogen fertiliser inputs.
Lambs reared on more diverse, lower input swards grew significantly faster, were slaughtered earlier and had a higher kill-out percentage than those reared on higher nitrogen input perennial ryegrass.
Worm burden
In addition, it was found that lambs that grazed multi-species mixtures had a lower intestinal worm burden and required fewer doses of anthelmintics during their life cycle, than those that grazed monoculture swards.
This is of particular importance given that ever growing global problem of increased resistance to anthelmintics
While the mechanism that leads to reduced worm burden is poorly understood, historically, species such has chicory were used in swards due to their anthelmintic properties.
Ewes also benefited, with live weight and body condition scores higher at key points in their life cycle, when compared to those grazing on monocultures. All swards were stocked at 12.5 ewes per hectare and all ewes were rearing twins.
Wider environmental benefits of multi-species swards were also evident through their support of greater abundance and diversity of a number of key invertebrate groups such as earthworms, which have hugely beneficial impacts on soil fertility and structure, and beetles, which are often important predators of insect pests.
Level of weed encroachment in many of the multi-species swards was lower than in the ryegrass swards, while estimated emissions of the potent greenhouse gas nitrous oxide per tonne of herbage dry matter produced from the low input swards was only approximately 10pc of the higher input perennial ryegrass swards.
This was due to a combination of the lower levels of N fertilizer used, the type of nitrogen fertiliser used, ie urea, and the high dry matter yields achieved from the multi-species swards.
Given the exciting, positive scenario these findings present for both farmers and the environment, UCD are currently establishing a long-term grassland systems experiment with hydrologically isolated (separated from surrounding soil water) paddocks at UCD Lyons Farm.
This national facility will be used to assess the sustainability of Irish grass-based agricultural systems through investigation of the interactions between three different pasture types, animal production, the environment, labour and farm economics.
The three pasture types to be investigated are 1) perennial ryegrass monoculture; 2) perennial ryegrass and white clover; and 3) a multi-species mixture. This long-term pasture research platform which is already attracting international interest, will be the first of its type in Ireland and will complement similar international facilities. This facility is necessary to inform future practice and policy for a unique and resilient Irish agriculture. Read more: www.smartgrass.ie
LAMBS REARED ON THE MORE DIVERSE, LOWER IMPACT SWARDS GREW FASTER, WERE SLAUGHTERED EARLIER AND HAD A HIGHER KILL-OUT RATE
Dr Helen Sheridan is the principal investigator on SmartGrass and lectures in Agricultural Ecology and Policy at UCD email: Helen. sheridan@ucd.ie