Potato growers who want to more accurately meet their 2021 contract obligations should consider the use of managed fertilizer applications to manipulate tuber size and increase marketable yield, according to new field research investigating the use of a stabilized amine nitrogen (SAN) technology that’s now available to U.S. growers.
The research, conducted in the United Kingdom – responsible for nearly ten per cent of European potato production – showed that by deploying a carefully managed SAN application schedule during the growing season, growers could easily and accurately manipulate tuber size to suit a particular market – chipping, frying, salad and so on – while increasing marketable tuber numbers by up to 16 per cent.
“Many growers will already be aware that not all types of nitrogen are created equal,” says Dr David Marks of Levity Crop Science, who conducted the research and presented the results at this year’s Crop Production in Northern Britain conference.
“We’re accumulating more and more evidence that even when the total amount of nitrogen supplied to the crop is the same, the form of nitrogen in which it is applied – nitrate, ammonium, urea, amine – can significantly influence crop growth and final yield,” he explains.
This is because important plant regulatory functions exhibit specific characteristics in response to different forms of nitrogen. Recognizing this appearance – known as the ‘phenotype’ – is key to using nitrogen more effectively and more efficiently, says Dr Marks.
“For example, use of nitrates stimulates leafy growth and apical dominance – meaning that vertical growth is greater than lateral growth. Not only does this result in the characteristic ‘leggy’ appearance, but it also inhibits lateral root production.
“Ammonium, meanwhile, leads to plants with the same amount of biomass as nitrate-treated crops but more of the biomass tends to be found in the roots and tubers.”
By understanding these differences, growers can create more resilient crops, says Dr Marks. “Shorter plants with more roots are more resistant to stresses such as drought or lodging,” he explains, “while plants with more roots are able to scavenge a greater volume of soil for the nutrients and water required for above-ground growth in later development stages.”
However, it’s often difficult for growers to distinguish between these different phenotypes. Typically, several different forms of nitrogen are present at any one time because conventional fertilizers – nitrate, ammonium, urea – are environmentally unstable and mostly degrade to nitrate, irrespective of the form in which it was originally applied, often creating other polluting breakdown products in the process.
Levity’s research, however, offers a ‘third way’: a third phenotype, initiated by urea amine. Exhibiting increased root production, reduced stem elongation, increased chlorophyll content before and after tuberization, plus increased above-ground biomass and raised chlorophyll levels at bulking.
“The difficulty is that bacteria in the soil rapidly convert urea into carbon dioxide, ammonia and nitrate within hours of application, whether to the soil or as foliar sprays,” points out Dr Marks.
To avoid this problem, and allow the third phenotype group to flourish, Levity has developed a chemical method that stabilizes ureic amine so that it persists in this form, whether foliar or soil-applied. It was this technology that the most recent set of trials looked to validate.
“By changing the number and scheduling of applications, we’ve demonstrated that it’s possible to easily manipulate tuber size distribution in the field,” claims Dr Marks.
Application regimes began in late June. All SAN treatment regimens significantly increased mean marketable tuber numbers in comparison to conventional controls. Mean marketable yield was increased by nearly six per cent.
“We’re delighted to help U.S. potato growers benefit from this research,” says Mike Williams, CEO of OMEX® USA. The Californian company – long-time experts in crop, fruit and vegetable nutrition – has licensed Levity’s SAN technology, formulating it within its Cell Power SizeN® products.
“This paper makes fascinating reading and reinforces the early research that helped us make the decision to use David’s technology,” enthuses Mike. “We think this is something that can really help growers get ahead and maximize the potential of their crops, particularly as U.K. and U.S. growers share many of the same varieties.”
Mike says that by compiling a revised fertilizer application schedule featuring SAN, growers will be able to better meet the demands of each market. “For example, making SAN applications early, pre-tuberization, leads to an increase in smaller tubers, those between 1½ and 2½ inches. On the other hand, if growers omit that early application and apply SAN at bulking stage, they’ll see an increase in the percentage of larger tubers in the 2½ to 3¼ inch category.
“What’s more, this shift in yield content does not come at the price of a smaller yield number or weight; yield is increased over and above that attained using standard agricultural practice,” Mike notes.
Mike’s encouraging U.S. growers interested in deploying SizeN® for the 2021 crop to contact him for more information on developing appropriate schedules.
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