Janice recently attended a Campaign for the Farmed Environment Maize Workshop to find out about the latest developments in Maize growing.  This newsletter summarises the latest findings.


This year has been a testing year for maize ripening and many farms have ended up harvesting too late.  Some farms have questioned if they should be growing the crop on their farms at all.

Due to ongoing pressures of soil erosion the Maize Growers Association are making their variety selector program available to all maize growers this year.  This guide helps you determine if individual fields on your farm are suitable for maize growing, and if so which maturity class you should be using.

It is easy to use and we recommend that you do this prior to purchasing your maize seed for next year.  If your field scores higher than 12 then you should question if you should be growing the crop in that field.  A copy of the input form is attached and if you need assistance please ask us.

There was much discussion over the variety lists and we were encouraged to look at:

  • Select the appropriate MGA maturity group for your field
  • Early vigour is an important trait – especially in a challenging year such as this one
  • If possible look at a couple years’ lists to identify varieties that perform well in more than just one year
  • Consider varieties that perform well in a challenging season such as this


The sooner you drill the crop, the sooner it will be harvested - as long as the soil temperature and soil conditions are right.

MGA did some work in 2010 showing that drilling on 10th April compared to 10th May resulted in:

  • 20% increase in dry matter yield
  • 6% increase in dry matter of crop
  • 5% increase in starch level
  • 50% increase in starch yield

But it is important that the soil temperature at 4” is at 8oC for at least 5 days prior to planting, and that soil and weather conditions are suitable for drilling.


Growing maize under plastic costs an additional £120-130/acre to grow and will therefore add on an extra £8-12/t onto the cost of growing the crop.  So is it worth it?

Results of trials carried out in Northern Ireland this year were presented showing that putting maize under plastic resulted in the following compared with the control:

  • Flowering was 16 days earlier
  • 2.8 t/ha higher fresh weight yield
  • 5% increase in DM
  • 60% increase in starch
  • 25% increase in MJ ME/ha

However, it was highlighted that these trials were likely to be undertaken on marginal maize ground, and in good maize growing areas the difference may not be so significant.

We have had some clients growing maize under plastic for the past 2-3 years and our observations are:

  • Definitely pulls forward harvesting date – which is important if you want to establish another crop before the winter and/or you need to make sure that late harvesting does not cause issues on the roads.
  • Effect on overall yield and starch levels vary considerably from year to year.  More yield and starch cannot always be guaranteed. 
  • Generally you need to get an additional 1.2tDM yield/ha in order to pay for the extra cost of drilling with plastic.
  • Pre-emergence weed control can be an issue in very dry conditions and spraying once the plastic is gone is often too late.  One farmer had a particular problem when following an oilseed rape crop.

There is still much work to be done on the cost benefits of growing maize under plastic, and apparently there are some maize varieties you should not grow under plastic, so check with your agronomist. 

If you farm on marginal sites it is worth looking at the cost of growing maize under plastic versus wholecrop wheat.   Whole crop wheat is generally more competitive but if you want us to cost this out for your farm let us know.


Runoff from maize fields is becoming a big issue.  As from 1st January 2015 there were 3 new soil GAECs introduced. Failure to comply with these can result in a deduction of your BPS payment.  They are:

  • GAEC 4 – provide minimum soil cover.  Maize stubble is an acceptable soil cover.
  • GAEC 5 – minimising soil erosion
  • GAEC 6 – use appropriate practices to maintain the levels of organic matter in soil

GAEC 5 is the big one in relation to growing maize, in that you must put measures in place to limit soil and bankside erosion.  Where soil erosion occurs there could be penalties on your BPS depending upon the severity of the problem and how much you have done to try to prevent it.

Trials carried out by MGA/IGER showed the levels of runoff from maize stubble following various management practices:


Management Practice

Amount of Runoff (litres)



Undersown with grass


Cover crop after maize


Chisel ploughing field


Clearly chisel ploughing had the biggest positive impact on reducing runoff, but this did lead to more nitrogen leaching from the soil profile.  It is however, in some fields possible to chisel plough only sections of the field i.e. around gateways which would have a big impact on soil erosion onto roads.

Undersowing with grass reduced runoff significantly and led to a green crop to plough down to benefit the following crop.  But undersowing should not come at the expense of maize crop yield.

The Danish are leading the way in terms of undersowing maize, so it is to them that we are looking to learn from all their work.

It is important that the undersown crop must germinate fast and become established before the maize closes the rows (normally beginning of July).  But the crop should not be so vigorous that it competes with the maize.

The best grasses to use are:

  • Italian ryegrass – sowing late June
  • Perennial ryegrass – sowing late June
  • Cocksfoot – ideal in droughty areas
  • Tall fescue – best for early sowing at same time as maize

When drilling grass from 6th June onwards there was found to be no significant reduction in maize yield except in fields which had low fertility – i.e. hungry continuous arable fields.

If there are low levels of weed the recommended procedure for establishment is:

  • Spread slurry and drill maize
  • When maize at 1-2 leaves control weeds
  • When maize at 4-5 leaves harrow and sow tall fescue
  • When maize at 7-8 leaves spray again if necessary

If there is a high level of weed the recommended procedure for establishment is:

  • Spread slurry and drill maize
  • When maize at 1-2 leaves control weeds
  • When maize at 4-5 spray again and harrow
  • When maize at 7-8 leaves harrow and sow PRG/cocksfoot

 Seed rates of 6-8kg grass seed/ha are being used and we saw some fields that had been established using an Einbock harrow with tines removed and the seed broadcast.

 Broadcasting the seed in this way usually results in establishment of around 8-18%, whereas direct drilling would increase this to 35-64% establishment – but we have yet to design a machine that will do this – watch this space!

 Other issues to consider to reducing soil erosion are:

  • Timeliness of field operations – do not travel on the ground when it is too wet!
  • Tyre pressure – run tyres on the lowest pressure recommended by the manufacturer
  • Use wide tyres when and if possible
  • Assess fields post harvest to identify problem areas
  • Dig a hole and look at soil structure
  • Subsoil as and when necessary