Directing the traffic – How to improve tuber size in potatoes.

In both Europe and North America the season started with poor weather, and potatoes were planted much later than usual. Markets are unforgiving and growers will be still asked to produce the right size tuber for the market. This will be challenging, as potatoes grow at their own pace and will likely be harvested at a similar date to normal this year.

Here we discuss two ways farmers can help push for a larger tuber size by using two novel fertilzers – Lono and Damu.

Directing the traffic

Yield in root crops comes down to two things. How much the plant grows, and where the plant allocates that growth.

A lot of time and resource is spent in getting growth out of crops (fertilisers) and in protecting that growth (pesticides) but far less work is done on ensuring the growth is in the right place. Understanding how crops allocate resource is key to getting better results in root crops, and this knowledge can help increase tuber size.

Amine nitrogen can influence tuber size

Plants can use nitrogen supplied as nitrate (NO3), ammonium (NH4) or amine (NH2) forms. These forms are all very different chemicals, are processed in different parts of the plant, using different processes and make the plant grow in different places.

Farmers do not see much difference between fertilisers supplying different nitrogen forms, as they mostly end up being absorbed as nitrate due to their instability in the environment post application.

Lono supplies amine nitrogen in a stable formula, research on potatoes shows that it influences growth partitioning in potato crops, whereby the potato focuses on tuber development rather than foliage growth when it is applied.

Lono applied during bulking strongly influences the size of tubers by pushing the plant towards growing the tubers rather than pushing vegetative growth. There are links to some of my research papers at the bottom of the article.

Independent data

Lono is a tried and tested product, used on potato crops on five continents with multiple research papers and many independent field trials available.

Boron can can influence bulking

Boron is often described as not being phloem mobile (similar to calcium), but this is only partially true. Boron is able to bind with some carbohydrates and has an influence on flow of carbohydrates from leaves to roots.

During bulking potatoes use boron to form bis-sucrose-borate which is translocated through phloem to the tubers and converted to starch.

However the speed at which this process occurs is a limiting factor to:

  1. How much boron can be applied to foliage (high concentrations in leaves cause toxicity)
  2. How much carbohydrate transport can occur to bulk tubers.

Levity’s Damu is a boron product that uses propriety chemistry to speed up the metabolism of the boron. This chemistry can be used to ‘direct the traffic’ of carbohydrates in the plant, increasing the flow of photosynthates from the leaf to the tuber.

Damu works by improving the translocation of sucrose between leaves and tubers for higher starch formations. Damu applied during bulking supplies the Boron needed to fuel carbohydrate translocation alongside Levity’s proprietary stimulant ‘Catalyst’ which stimulates the speed and intensity of the process.

Single foliar 5L/Ha applications of Damu ahead of harvest push photosynthates that would otherwise be left in the leaf into the tuber, increasing average tuber size.

Independent data

Here we show data taken from a 2020 Independent trial on New Zealand on the processing variety Agria. A single 5L/Ha foliar application of Damu shifted the size of potatoes to an higher average size grading.

The yield in the control area of marketable size tubers (+45mm) was 81MT/Ha compared with 92MT/Ha in the Damu treated area, an 11MT yield increase.

The efficacy in Damu comes from moving carbohydrates in the leaf down to tubers ahead of harvest, so that photosynthates produce yield rather than being left in the field in discarded foliage.

Recommendations for improving tuber size


Apply 3 applications Lono (either foliar of via fertigation) during early, mid and late bulking at 5L/Ha.


Apply Damu (foliar) 2 weeks ahead of harvest at 5L/Ha.

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Award winning scientist and experienced agronomist. With multiple patents, and proven track record of product development in biostimulants, pesticides and fertilisers.

Author: David Marks

Managing Director, Linkedin Profile