Farmers will be considering their reseeding options over the next month, especially to repair fields damaged since last year’s poor weather conditions.

Apart from conventional reseeding, another option is sowing a multi-species mixture.

Experimental work is currently being undertaken at AFBI Crossnacreevy.

Danielle Varley from AFBI says that synthetic nitrogen fertiliser does provide readily available forms of N but it can be easily lost through surface runoff, leaching and as gaseous forms such as nitrous oxide.

However multispecies grassland swards, comprised of grasses, legumes and herbs, have recently gained traction as a potential solution to decrease N2O emissions and improve N use efficiency.

The Multi4More project is a DAERA-DAFM funded research collaboration between AFBI, Teagasc, UCD and TCD. A common field experiment was established at AFBI Crossnacreevy, Teagasc Johnstown Castle and UCD Lyons Farm. The project aims to evaluate the ability of multispecies grasslands sward to reduce synthetic N fertiliser use and N2O emissions, while improving N use efficiency without a loss in yields.

Multispecies grassland swards have the potential to: reduce greenhouse gas emissions, produce higher yields at lower N input compared to grass monocultures, enhance animal performance, improve soil fertility and build tolerance to environmental disturbances, such as drought.

However, Danielle says research is required to generate N2O emission factors for multispecies mixtures grown in Irish soil and climatic conditions.

Legumes, such as white and red clover, are capable of fixing N from the atmosphere, which is then shared with neighbouring plants. While herbs, like plantain possess compounds that can inhibit a N2O production pathway. Additionally, herbs such as chicory can enhance yield productivity.

In May 2023, 111 experimental plots were established at AFBI Crossnacreevy to assess N2O emissions and yield of multispecies grassland swards. Experimental plots were sown with varying proportions from 0 to 1 of perennial ryegrass, timothy, white and red clover, plantain and chicory.

The N fertiliser treatments under study are 0, 75, 150 and 300 kg N ha-1 yr-1. In April 2024, measurements of N2O emissions began and will continue for two years until 2026 to calculate the emission factor of various species compositions. Five harvests are carried out annually to assess agronomic properties, such as dry matter and N yield.

She said multispecies grassland swards have the potential to lessen dependency on synthetic N fertiliser while producing comparable yields to high N fertiliser input grass monocultures. Multispecies can also enhance tolerance due to weather variations brought on by changes in the climate. Additionally, multispecies swards may be able to lower greenhouse gas emissions and nutrient leaching, thereby supporting sustainable agricultural practices.