Getting the soil balance right was the key theme addressed by Teagasc’s Mark Plunkett at the recent Alltech Crop Science seminar. The Johnstown Castle-based research scientist confirmed that losing sugar beet out of our traditional crop rotation practises has been a big factor in reducing fertility levels throughout Ireland’s tillage sector.

“Improving soil fertility is a long term process,” he further explained.

“It could well take a generation to get matters right and the wide scale practice of growing crops on conacre ground doesn’t help matters at all in this regard.”

The Teagasc representative stressed repeatedly that regular soil testing is the all- important starting point to every fertiliser programme carried out on a tillage farm.

“Teagasc tests approximately 40,000 soil samples per year. This, in turn, gives us a unique insight into soil fertility trends throughout Ireland,” Mark commented.

“The latest results are telling us that 55% of tillage soils are at a pH level which is below the optimal 6.5 figure required for optimum crop production. What’s more, soil P & K levels have been declining between 2007 to 2012 with indications of improvements in 2013. In fact only 14% of Irish tillage soils are within the optimal range when it comes to their combined pH, P Index and K Index values for optimum soil fertility.

“This means that Irish tillage farmers have a lot of work to do in order to improve the very basics of their soils’ fertility levels. Growers should target to have their soils at a P & K Index 3 to maximise crop yield potential annually”.

He continued:

“Soil testing should be carried out every three to five years with a focus on determining  pH, Lime Requirement, Phosphorpus, Potash, Magnesium, Manganese, Copper and Zinc levels. It is also important that soil samples are taken correctly to ensure reliable soil test results”.

“Soil organic matters should also be assessed to comply with farm cross compliance.”

Mark Plunkett went on to point that soil test results are not being fully utilised on many tillage farms in tailoring fertiliser and lime advice.

“Allowing them to gather dust in a farm office is totally self defeating. The reality is that the results of a soil test, and the trends identified on farm over a number of years, can help tillage farmers save considerable sums of money when it comes to deciding on their fertiliser strategies. It costs very little to have a comprehensive soil test carried out.”

He continued:

“Lime is the best value fertiliser that can be applied on the very large numbers of Irish farms where soils are acidic. Each soil will have its own lime requirement depending on soil pH and crop type.  He recommended that lime should only be applied based on an up to date soil test result”.

“Contrary to popular belief finely ground limestone will act immediately to improve soil pH values. Significantly, this will also lead to improved N and P availability for crops.”

With regard to fertiliser application strategies Mark Plunkett pointed out that farmers must start with assessing the crop offtake of the various nutrients and then factor in an additional amount to boost soil index levels, if required.

“It’s important to use compounds or blends with the right P:K ratio,” he commented.

“Organic manures are a very important source both major and minor nutrients while also adding significant amounts of organic matter.  Target organic manures to low fertility fields to help build soil P and K levels cost effectively to the target soil P and K index 3.  High N manures such as pig or poultry manures should be ploughed in immediately so as to minimise nitrogen losses.”

Mark Plunkett concluded:

“Sulphur is an important nutrient in grain and oilseed production and in the last number of decades there is less sulphur coming from the atmosphere.  Crops grown on  light / low organic matter continuous tillage soils are most responsive to sulphur.  The best time to apply sulphur is in early springtime with the main N applications”.