Agronomy study

The aims of this experiment were to identify the optimum mixture for yield and quality (annual and seasonal yield and quality), to identify the optimum fertiliser rate for that mixture and to investigate the effect of varying levels of nitrogen input on nitrogen use efficiency of multispecies swards compared to perennial ryegrass only swards.

A simplex designed experiment with eight pasture mixture with differing proportions of nine species from three functional groups was set up. The functional groups included were grasses, legumes and herbs. The three grasses selected were perennial ryegrass, timothy and cocksfoot, the three legumes were white clover, red clover and birdsfoot trefoil and the three herbs were plantain, chicory and yarrow. The eight mixes were repeated at three levels of richness with level one having one species from each functional group, level two having two species from each functional group and level three having three species from each functional group. Each of the 24 mixes were repeated at four nitrogen fertiliser rates (0, 45, 90 and 135 kg N/ha/year).

A study replicated four times with a perennial ryegrass monoculture, perennial ryegrass and white clover mix, a simple six species mix and a complex nine species mix, all receiving 90 kg N/ha/year was set up also. This was compared to a perennial ryegrass only sward receiving 250kg N/ha/year. These plots (1.5 x 10m) were simulated grazed for 2014. This was repeated in bigger plots (10 x 10 m) for actual grazing by animals in 2015 to compare simulated grazing versus actual grazing on annual and seasonal dry matter yield in multispecies swards versus perennial ryegrass only swards.

The plots were sown in UCD Lyons estate in September 2013. Post establishment the plots were harvested every 28 days from April to October 2014 under a simulated grazing routine and this experiment will continue in 2015. Samples were taken from each plot at each harvest for dry matter determination and chemical composition.