Maize under stress
Growers who are suffering with dead or dying maize crops have been advised to harvest the crop at the earliest opportunity. Waiting for a later harvest in the hope of higher yields and more starch is likely to be counterproductive.

This advice comes from independent silage specialist and microbiologist, Dr David Davies, who says crops in very poor condition because of this summer’s drought will not recover, their cobs are unlikely to set, and the crop will not provide a good level of starch.

He says: “If your maize is showing signs of dried and shrivelled leaves, it’s unrealistic to expect a recovery.

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

Instead, he says growers should cut their losses and harvest what remains of their crops.

But he warns that a damaged crop is far more susceptible to fungal infection, which can rapidly take hold of plants which are stressed and dying.

“The crop’s defences will be low so colonisation by fungi will be far easier, especially if the crop damage is followed by rain,” he explains. “This has the potential to increase mycotoxin production and aerobic spoilage losses, either during the initial harvest or during feed-out from the clamp.”

For this reason, growers are advised to take particular care with the preservation of maize silage this season. This includes the careful selection of an additive and thorough compaction and sealing at the clamp.

He says: “The fermentation will be more difficult than a normal maize as the ash content will be higher and the greater challenges from yeasts and moulds will increase the challenges at feed-out from aerobic spoilage.

“Aerobic spoilage will be a major concern, so additives that contain chemicals to inhibit the aerobic spoilage organisms are the only ones that will not compromise fermentation quality.”

Kelvin Cave Ltd concurs with Dr Davies, and says they’d recommend a preservative from the Safesil range for forage made and stored in these conditions.

Michael Carpenter, the company’s technical director, says: “Making maize silage successfully in the face of such difficult conditions requires attention at every step of the process, as there’s so much potential for spoilage and dry matter loss.

“Rather than trying to out-compete undesirable microorganisms, as is the case with biological inoculants, the human-food grade, chemical preservatives in the Safesil range work by eliminating them at the outset.

Using a SilaPactor can increase the density of maize silage by at least 20%.

“The additional use of a SilaPactor to consolidate the maize applies tonnes of extra weight to the clamp, which excludes far more air than a tractor alone,” he says. “This can be expected to increase the density of maize silage by at least 20 per cent.”

However, Dr Davies warns growers to expect a lower feed value from their drought-stressed maize crops
this season.

He says: “Harvesting forage maize where cobs have not formed is likely to yield little, if any, starch.

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

This phenomenon was demonstrated in South-Eastern Europe during a recent drought and extreme heat, when the maize crop was harvested far earlier than was standard practice.

He says: “Whilst this resulted in a reduction in starch and overall energy, there was some improvement in total rumen degradable fibre, leading to relatively similar metabolisable energy in the maize [see table below].

“This helped overcome some of the issues of reduced starch, and improved the suitability of the forage for feeding to lactating dairy cows,” he says.

Michael Carpenter emphasises the importance to growers of making the best of a bad job this season.

He says: “The pressure on forage stocks is continuing and the increases in production costs show no sign of abating, so reducing dry matter losses from forage this year is more important than ever.

“I have seen many crops across the UK which are clearly suffering from heat and drought stress and should be harvested straight away,” he adds.

Dr Davies also remarks that contrary to common belief, maize is more susceptible to heat damage than the cereal crops which have historically been grown in the UK.

He says: “Recent studies have shown that a 1oC rise in global temperatures will see a global reduction in the production of soybeans by 3.1%; wheat by 6.0% and maize by 7.4%.

“Whilst we think of maize as a plant for hot places the effect of heat on the plant is greater than that on wheat,” he says.

Average (mean) farm silage analyses comparing heat/drought-stressed maize in 2013 to a more typical growing season in 2014 (South-Eastern Europe)

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