Farm Ireland

Monday 11 December 2017

The answers still lie in the soil. But are we asking the correct questions to boost crop yields?

John Shirley

'The answer lies in the soil' was once a common refrain in Irish farming. Prior to the widespread use of fertiliser and drainage, land quality and depth of soil were paramount in farmers' thinking.

Some land was known as good bullock fattening land. Other ground was deemed to be only capable of fattening heifers. Some land was deemed tillable, while on other soils farmers wouldn't let a plough in the gate.

Early Irish agricultural research also prioritised soils. One of the first tasks of the newly formed Agricultural Institute more than 50 years ago was to embark on the detailed county-by-county National Soil Survey of Ireland.

This detailed analysis was suspended around 1980, when about half of the counties were completed. The science of soil was downgraded as more attention was placed on crops and the animals which were above the ground. There was almost an assumption that all soils could be made equal by fertilisers and drainage.

Many would say that the balance moved too far away from the soil.

Now the pendulum has very definitely swung back to watching what's happening in our soils. Farmers must now carry out routine soil testing and we have to account to big brother for every shake of fertiliser or dung that is applied on our fields.

There was also a renewed interest in field drainage this year as farmers sought to address the field problems encountered during the deluges of 2007-2009.

At research level, Teagasc has set out to complete the abandoned National Soil Survey. Also, the Teagasc crop research centre at Oakpark in Carlow has joined with Johnstown Castle in Wexford under the programme banner of Crops, Environment and Land Use.

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Dr Noel Culliton, the head of this programme, denied that this was a shotgun marriage of convenience to accommodate Teagasc cutbacks.

"There is a logic to the coupling of soils, crops and the environment. Soil and soil nutrients have become a huge issue in the light of environment legislation, most of which is coming at us from Brussels. When negotiating with EU officials on environmental issues for Irish farmers, we must have scientific facts to back our stance," said Noel.

"Even if there wasn't legislation, it makes sense to get the most efficient use of fertilisers and other soil inputs.

"In Johnstown Castle, we now have scientists working on hydrology (soil drainage) and on pedology (soil compaction). We have set out to complete the National Soil Survey. This time we will use satellite imagery supported by field visits to carry out the task."

Also at Johnstown Castle, they are working on a soil test that will predict nitrogen availability, thus indicating what sort of season-long top-up is needed. Dr Culliton believes this would give a huge boost to fertiliser efficiency.


Over the past decade, Irish farmers have reduced nitrogen use by almost 20pc, but phosphate usage is down by a whopping 40pc. In Northern Ireland in 2008, nitrogen usage of 82kg/ha was the lowest since 1975.

This suggests that fertiliser is being used more efficiently, which is smart. But there are also signs that farmers have gone too far in cutting down on phosphates and that crop and silage yields are being hit.

"Phosphate is like oil, supply is running out. Soil samples over the past four years indicate that phosphate deficiency (Index 1) is on the increase. We should aim to keep our P level at Index 3. It's a good long-term investment," said Dr Culliton.

Six years ago, when controversy over the Nitrates Directive raged, Teagasc was caught with insufficient data on the problem and a restrictive regime was imposed on Ireland. In the interim there has been more research and measurement. Both have brought concessions in the Nitrates Directive, with some easing on phosphate application thrown in as well. Teagasc science also helped to get changes in nitrogen usage in malting barley.

The EU, being itself, continues to poke its nose into the minutiae of our soils, fertiliser and crops. Coming down the tracks, we have the soil organic nitrogen issue, we have the 'greening' element of the single farm payment, plus we have the issue of nitrous oxide emissions.

As a greenhouse gas, methane is regarded as 20 times more harmful than carbon dioxide, but nitrous oxide is deemed to be 320 times more damaging. The early research on nitrous oxide emissions suggests that they are higher from damp heavy soils and that CAN is more vulnerable than urea.

Dr Culliton is well aware that Teagasc must collect the facts to counter potentially damaging edicts from Europe, but he also sees the bigger agricultural challenge of feeding the burgeoning world population.

His research colleague John Spink reckons that crop yields on farms have reached a plateau despite the continued advances from plant breeders. He said that this was happening in other countries as well.

"Is this because soils are not properly managed? Is it plant nutrition? Or husbandry? Or a combination of all of these?" Mr Spink asked.

He added that, in theory, wheat is capable of yielding up to 25t/ha and oilseed rape 9t/ha -- over twice the levels our best farmers are achieving.

So, as we approach 2012, I would argue that the answer is still in the soil. But are we asking the right questions?

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