Maize growers advised to harvest struggling crops early

Growers should harvest struggling maize crops earlier this year and take particular care with preservation to minimise further spoilage losses.

Silage specialist and microbiologist David Davies says holding out until a typical harvest date, if the crop is already dying off due to hot and dry conditions, will be counterproductive.

“If your maize is already showing signs of dried and shrivelled leaves, it’s unrealistic to expect a recovery,” says Dr Davies.

“Waiting may compromise the entire crop and leave you with nothing of value.” 

See also: How maize undersown with grass provides two-fold benefit

He also warns that a damaged crop is more vulnerable to fungal infection, so thorough compaction at the clamp and appropriate use of additives will be necessary.

“The crop’s defences will be low so colonisation by fungi will be far easier, especially if the crop damage is followed by rain.

“This has the potential to increase mycotoxin production and aerobic spoilage losses, either during the initial harvest or during feed-out from the clamp,” he adds.

Drought-stressed maize

© Michael Carpenter

Fermentation challenges

In damaged maize crops, the ash and protein content will be higher, making fermentation more difficult.

This, combined with greater challenges from yeasts and moulds, will increase the risk of aerobic spoilage at feed-out.

“Additives that contain chemicals to inhibit the aerobic spoilage organisms are the only ones that will not compromise fermentation quality,” advises Dr Davies.

Michael Carpenter, technical director at feed and forage preservation specialist Kelvin Cave, says there is a high potential for dry matter loss this year.

“Rather than trying to out-compete undesirable microorganisms – as is the case with biological inoculants – our human-food grade, chemical preservatives work by eliminating them at the outset,” he says.

Maize susceptibility to heat

David Davies says maize is more susceptible to heat than many believe, and is often affected more than a wheat crop.

Recent studies have shown that a 1C rise in global temperatures will see a global reduction in the production of:

  • 3.1% soybeans 
  • 6% wheat 
  • 7.4% maize.

Energy trade off with early harvest

Dr Davies counters concerns that early harvest will reduce starch content and energy of the silage.

“Harvesting now as a wholecrop does compromise starch content, which is likely to be negligible if cobs have not successfully formed.

“However, there are gains to be made in terms of the drought-stressed crop’s fibre, and its degradability,” he comments.

This has been demonstrated in south-eastern Europe with earlier harvesting in drought conditions.

Results showed that a reduction in starch was balanced with an improvement in rumen degradable fibre, resulting in a fairly similar metabolisable energy.

Comparison of silage analyses in south-east Europe in drought and non-drought growing seasons


Heat/drought-stressed maize in 2013 (mean figures)

Maize grown in a more typical season in 2014 (mean figures)

Dry matter (DM) %



Starch g/kg DM



Metabolisable energy MJ/kg DM



Neutral detergent fibre (NDF) g/kg DM



Rumen degradable NDF % of total NDF



Total degradable NDF g/kg DM



Source: Silage Solutions