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Boost profits by making efficient use of fertilisers

On farm, this year's most significant difference compared to 12 months ago, and 2010 for that matter, is the amount of pasture cover farmers have on the milking block.

On our own farm, grass growth was evident during the winter months and we now have an exceptionally high average cover due to the wet autumn in north Kerry.

However, the pasture quality is good, with no winter kill and limited burn. Looking around, this seems to be the case for a number of farmers.

This could be considered as equally advantageous as extra silage in the pit or, dare I say it, extra money in the bank as it has the potential to substantially reduce concentrate feed bills through this spring, which may be an ideal scenario on a farm which has exceeded its milk quota.

At this time of year, the use of nitrogen (N) fertiliser is being given due consideration. Promoting grass growth is important where stocking rates on the milking platform are moderate to high, especially where a dairy herd is calving compactly.

However, last year's financial accounts have highlighted fertiliser expenditure as a high and ever-increasing cost, so it's important that we continue to educate ourselves on ways to improve the efficiency of its use. The decision tree (right) can help ask a few practical questions which will give clarity to fertilizer use at farm level.


A common question at discussion groups throughout the grazing season is what type of fertiliser should be used. This can be difficult to answer as the overall efficiency of N recovery is influenced more by site than by N form.

However, there are a few factors that may help to minimise the losses of inorganic N from ammonia gas volatilisation, denitrification and leaching:

-The efficiency of N is limited by other nutrient deficiencies -- the main nutrients being phosphorous (P), potassium (K) and sulphur (S) -- especially where high rates of nitrogen are used, so consider your soil test values. The reduction in efficiency is limited with regular P, K and S maintenance dressings.

-Soils have a finite capacity to store N in their organic matter, therefore higher dressings of N will inevitably result in increased losses.

-Urea can be less reliable and often has a lower efficiency due to N losses from ammonia volatilisation. Many experiments have found consistent yield losses of 6-8pc (when compared to ammonium nitrate) as urea is weakly absorbed by the soil. However, due to the cheaper price of the product, this lower efficiency is often accepted by farmers.

Dr Mary Kinston is an agricultural consultant based in Kerry. Email:

Indo Farming