Growing maize after a wet season: Challenges and solutions

This year the amount of maize grown is predicted to increase by 20% to combat the shortage in winter cereals being drilled following the wet autumn.

Farmers Weekly and crop specialist Hutchinson’s organised a roundtable meeting with growers and experts to discuss the challenges and solutions of growing maize following difficult growing conditions last year. 

1. Variety selection

Challenges

  • Varying seasons: 2018 was very dry but 2019 was wet.
  • Farmers tend to change their maize variety based on the previous year’s growing conditions.
  • Last year some farmers opted for ultra-early maturing varieties and were caught out.

See also: 6-step guide to successful maize establishment

Solutions

  • Don’t take a knee-jerk approach when it comes to variety selection
  • Select a range of maturity dates to spread the risk.
  • Choose varieties that have undergone local trials to ensure they suit your local climate and soil type.
  • When comparing variety maturity dates (FAO score), be careful comparing numbers between different breeders as they all measure the FAO score differently. They can be compared within breeders, however.
  • If soil erosion is a risk don’t choose a late-maturing variety.
  • Remember the variety you choose accounts for about 10% of the yield but can depend on how far north you are located. Yields can reduce the further north you are as it becomes harder to grow larger biomass varieties that will not mature in time. The early maturing varieties tend to be a slightly lower yield.

2. Preventing soil erosion

Challenges

  • After a wet autumn and flooding this year, soil erosion may be an issue and can be a particular concern where the land runs near a watercourse.
  • Some crops were unable to be harvested in 2019 because the land was so wet.

Solutions

  • Maize should only be grown on land where appropriate. The Maize Growers Association (MGA) has developed a tool that will give a risk score for site selection based on several factors including rainfall and field. More information on the Maize Growers Association website   
  • Under-sowing with a forage crop can help prevent soil erosion. Trials in Cumbria found broadcasting grass in June/July on to the growing maize crop with a tall, self-propelled sprayer gave a cover that looked good enough to graze lambs on and helped prevent soil erosion.
  • If there is a lack of moisture in the soil, drilling grass may be a better option than broadcasting the seed but this can be limited by the crop height. Drilling can only take place at the start of the crop life (up to leaf 8) as machinery drilling can damage the crop after this stage.
  • If fields are prone to soil erosion or you have had difficulty cutting maize, you may need to think about harvesting grain maize – it is easier to get the crop off the field in wet conditions compared with using a forager with tractors and trailers.

3. Establishment – drying out fields and dealing with compaction

Challenges

  • Some fields may still be very wet.
  • Compaction could be an issue where the crop was harvested in wet conditions.

Solutions

  • Let the fields dry out before sowing your maize crop. Fields may require light, shallow cultivations to allow surface water to drain. However, don’t but go too deep as this can force the water downwards.
  • Dig a hole so you can get an understanding of where your plough pan is. This is the layer of soil that becomes compacted when people plough or cultivate to the same depth (normally 8-10in deep). Then set your cultivator to the correct depth to break it up.
  • Know what depth your subsoiler/cultivator is set at.
  • Don’t go any deeper than 1in below the plough pan in most circumstances.
  • Drill seeds east to west to help crops get the most sun.
  • On lighter land it may be necessary to cultivate the land more than once to allow it to dry thoroughly.
  • Beware of over-cultivating if using film. In this instance you want a finer, firmer seedbed as this improves pre-emergence efficacy thereby helping to minimise weeds.

4. Establishment – replacing nutrients

Challenges

  • Soil nutrients may have been washed away by prolonged rain and flooding.
  • The amount of leaching will depend on the soil type, with lighter soils more likely to have been affected.

Solutions

  • The MGA can send you nitrogen recommendations if you send them your soil type and history.
  • Soil sample your fields so you know the nutrient status.
  • In a lot of situations, no nitrogen may be required in the seedbed where fields have received manure. However, potash is very important.
  • When thinking about nutrients, maize is different to other cereal crops as it uses nitrogen later in the summer. In a field where FYM or AD digest is applied, residual nitrogen will be available to the crop later in the summer during the tasselling stage.
  • Dairy farmer Tom Fisher is applying FYM and no artificial P+K. His aim is to have a pH of 6.5. Liquid nitrogen or solid nitrogen may be applied later in the growing season depending on crop requirements. No starter fertiliser is applied as maize is grown under film. In a trial, Mr Fisher applied liquid N and saw a 3% improvement in the crop dry matter yields at harvest. The best time to apply late N either as liquid or solid, is late June/early July but it depends on the height of the machine applying it. This is to help grain fill and cob development that starts in late July/ August.
  • Alistair Wannop uses a slow-release fertiliser. This can help the crop to mature earlier.

See also: AHDB nutrient management guide

5. Establishment – weeds and pests

Challenges

  • Weed control under film can be difficult due to timing of applications.
  • Weeds were more of a problem in 2018 with the prolonged dry weather and reduced effectiveness of pre-emergence herbicide applications.
  • One of the main seed treatments, Mesurol, which is a bird repellent, has now lost its registration so there will be few seeds available with the treatment this season.

Solutions

  • Ideally, crops should be treated with a pre-emergence and post-emergence spray. The same applies for those growing maize under film, although you may have to wait until the weeds and the maize has broken through the film before the second spray is applied.
  • Anyone only applying a pre-emergence spray is taking a risk. Delaying spraying by two weeks can cost 1-2t/ha.
  • Film can be cut in weeks four to five to spray, but this isn’t ideal and should only be done where weeds are causing an issue. The seed treatment Korrit can still be used as a bird repellent, however care must be taken when using it as it is slightly more hazardous.

Roundtable who’s who:

  • Host farmer Alistair Wannop and his farm manager James Irvine, Linstock Castle, Carlisle. They grow 121ha of maize under film feeding an AD plant and are averaging 13.5t DM/ha and 43t/ FW/ha
  • Tom Fisher, Smalmstown Farm, Longtown. Running a large dairy herd. Grows 121ha of maize under film. He averages 16t DM/ha and 46t FW/ha at 30% DM
  • Willian Tuer, system manager at Tinwald Power. Growing 69ha of maize for an AD plant and looking to double the amount grown. Averaging 13.5t DM/ha
  • Jim Clark, Hutchinson’s area agronomist
  • Jonathan Bellamy, area sales manager for Corteva
  • Simon Draper, Maize Growers Association