The war for acres has begun already. Between seed companies, at least.

The close the year usually bring a battle of boasts, hyperbole maybe, between seed groups over the performance of their products in the latest US harvest – in the aim of winning farmers' custom for plantings of the next one.

Syngenta's announcement on Tuesday that its Agrisure Artesian corn variety, developed for drought resistance, had increased yields during "extreme" US conditions by 48% over "comparable" hybrids was only the latest in a series of claims by seed groups.

DuPont, the owner of the Pioneer seed business, kicked off the round of roistering nearly a month ago, claiming its best-selling corn seed had delivered an advantage of up to 26.5%, in south west Iowa, over "all competitors".

'Strong results'

Monsanto, the world's top seed group, kicked in last week by saying its DekaLB seed had delivered a yield advantage of up to 17.5 bushels per acre, over a Pioneer variety.

The overall DekaLB advantage was 8.3 bushels per acre, while that for its Droughtgard seed, modified for a high drought tolerance, was more than 5.0 bushels per acre.

"This season's strong results, even against the backdrop of the devastating drought we witnessed throughout the country, reinforce our ability to deliver on our commitments to our farmer customers," Robb Fraley, the Monsanto chief technology officer, told investors last week.

'Either matched or exceeded'

Meanwhile on Monday, DowAgroSicences, the agriculture arm of chemicals giant Dow Chemical, said that 2012 harvest results "reinforce the vigour" of the unit's "comprehensive corn breeding programme".

Its genetically modified seed "outyielded competitor hybrids by nearly 4 bushels per acre in US trials which, at today's grain prices, translates to a significant boost in potential income for farmers", the Indiana-based operation said.

"Corn hybrids from Dow AgroSciences either matched or exceeded yields of competitive drought-tolerant products in 2012 US trials.

Furthermore, it claimed, for a fourth successive year, to have raised its share of the North and South American corn seed market.

'Maximises yield'

Meanwhile, Syngenta said that its Agrisure Artesian variety also "matched or exceeded the yield of comparable hybrids", while outperforming particularly in severe and extreme drought conditions.

"These trials confirm that Agrisure Artesian not only delivers superior yield under drought stress, but also maximises yield in normal conditions," Davor Pisk, the Syngenta chief operating officer, said.

However, DuPont said that farmers growing its Optimum Aquamax corn "were rewarded in a particularly challenging year," Paul Schickler, the DuPont Pioneer president, said.

"The seed delivered a yield advantage under the most difficult drought stress and differentiated our product from the competition," he added, flagging yield advantage of 8.9% in comparison with more than 11,000 competitive products.

Not like-for-like

So which really is choice?

That is not so easy to answer, despite the apparent plethora of data, given the way it is presented – to suit the company concerned.

For instance, some yield advantages are expressed in percentages, as with DuPont or Syngenta, and some in bushels per acre, as with Monsanto, but not often given in both, which would allow easier comparison.

There are differing choices of comparator. Some results are compared with those an individual competitor seed, some with the average of a range of rival products, or some with a seed specific end of the price range.

And there are important differences in choice of battleground too. Some companies, such as Syngenta, are talking specifically of drought areas, some of geographical areas, some averaging results over continents.

Annual event

All this allows companies to keep blowing their own trumpets, year after year, without hitting a duff note.

But as for what growers are best choosing, well, there is nothing like local knowledge to counter blanket claims, and a decent long-range weather forecast would be helpful too.

And there are those rumours that the poor 2012 harvest, and the prospect of huge US corn sowings next year, means seed will not be in plentiful supply anyway...