Farm Ireland

Sunday 26 March 2017

Use slurries to reduce fertiliser bills

Michael Hennessy

St Patrick's Day is generally marked as a turning point for farmers. This date is used as a target date to either finish sowing or start sowing, depending on the type of land.

It's also seen as a point where fertiliser should be applied, or perhaps as a time for the second application. It's easy to say every year is different, but plant growth is perhaps a month behind normal. The past few days have helped the recently applied fertiliser to wash in and soils have warmed up a little.

At the time of writing, soil temperatures in the middle of the country are well behind normal, with some soils still struggling to reach 4°C. Growth kicks in at around 6°C which, hopefully, most soils will reach by the end of this week.

Large acreages of crops have been sown over the past two weeks in very good conditions. Growers will continue to focus their efforts on sowing spring barley, spring oats and other crops such as fodder beet, maize and peas. It's late to be sowing spring wheat or spring beans, and if sown now then be prepared to harvest the crop well into September.

Alternative crops such as maize, peas or fodder beet offer opportunities to save on fertiliser inputs and they also help break a rotation and freshen up land. The addition of slurries to these crops offers substantial savings in fertiliser where the slurries are close at hand.

At current prices (CAN €230/t and 0:10:20 at €340) 2,000 gallons/ac is worth €70/ac where 40pc of the nitrogen is used. Ploughing is required to trap the nitrogen to get the best from the slurry prompt. Research from Oak Park has shown that it's possible to utilise at least 50pc of the nitrogen in slurries when incorporated immediately (within six hours) after application.


The utilisation of nitrogen from slurries left on the surface unincorporated for a few days after application can be as low as 10pc.

This incorporation is especially important for pig slurries as these have a higher concentration of ammonia which is volatilised quickly once spread. Utilisation of P and K by the crop is estimated to be close to 100pc for slurry.

Farm-to-farm trade has taken on a life of its own over the past two years and tillage growers and livestock farmers are now realising the mutual benefit of this type of relationship.

Both farmers and merchants have cultivated businesses based around the model of growing and selling whole crop feeds.

For the customer the unknown quantity of a whole crop feed is the most troubling. Take barley or soya for instance. When a farmer buys these products the constituents are known and vary little from year to year.

Maize silage, on the other hand, can vary from well over 30pc dry matter with close to 30pc starch to lows of 20pc dry matter with very little starch.

Research carried out in Ireland suggests an optimum starch level of 25pc in whole crop maize for milk and beef production.

Maize variety selection is very important as this will dictate where it's sown, time of sowing and whether plastic is required or not. These decisions will greatly influence the dry matter and starch level of the harvested crop.

Growing maize close to the coast in Waterford or Cork is very different to growing maize on the Athboy side of Navan. One year with another, early maturing varieties such as Acclaim, Adante, or Avenir grown without plastic in the south of the country will reach the target dry matter and starch levels.

These same varieties will struggle if sown in less favourable sites, or if grown in the midlands or northeast. Sowing under plastic will help these varieties to mature but planting a late maturing variety in these sites under plastic should be avoided where high dry matters and starch is the goal.


Late maturing varieties such as Piazza will perform best when sown early under plastic in the best sites. Planting of maize under plastic can generally commence in a couple of weeks in favourable sites but delay sowing without plastic until mid April at the earliest.

Keep an eye on soil temperatures as maize will only move when soil temperatures are around 8°C or higher.

Irish Independent