A series of research trials involving Teagasc staff and colleagues at Queen’s University Belfast and the Agri Food Biosciences Institute is shedding new light on the uptake of Phosphorous fertilisers.

Some of the results obtained to date were discussed at today’s Walsh Fellowship Seminar, hosted by Teagasc and the RDS in Dublin.

Phosphorus (P) is an essential element for grassland productivity, but P fertilisers are mined from finite resources of phosphate rock. As a result, there is growing interest in increasing the efficiency of P fertiliser use in agriculture to ensure the future sustainability of food production.

Maintaining soil P fertility is critical if agriculture is to achieve the productivity targets set by Food Harvest 2020. The collaborative research project was designed to increase the available knowledge on  the behaviour of, and requirements of P in grassland soils.

Data from a long-term field experiment showed that a sustained annual application of 15 kg of P per hectare per  year was required for  maximum herbage yield, whilst seasonal trend indicated that P concentration in herbage  was lowest during summer months.

Results from a short-term field experiment carried out on two sites with contrasting soil fertility levels found a comparable response to nitrogen  and P on the herbage yield and soil P levels had a strong influence on herbage P  concentration.

Significantly, a soil incubation experiment carried out on a range of different Irish soils showed that lime plays an important role in increasing the availability of soil P and fertiliser P. In the same range of soils, the examination of soil P behaviour using a number of analytical techniques were investigated and the results highlight the  variation that exists in P dynamics across Irish soils.

Overall, the results from these experiments suggest that as the future availability of P fertiliser becomes uncertain, a greater emphasis on soil specific fertiliser P guidelines will be required to maximise P efficiency in grasslands. The research team believe that their work will underpin the rationale and provide an initial investigation for the future implementation of more soil specific P fertiliser guidelines in Ireland.

Fertiliser spreading on grassland. Photo O’Gorman Photography