Using Boron to Increase Tomato and Pepper Size

Boron is an important nutrient, but one that is tricky to get right owing to it behaving differently on each crop. Here we look at how boron works in tomato and pepper crops and explore how boron can improve fruit size in these crops.

Boron is frequently described as not phloem mobile, and a lot of agronomy is predicated on that assumption as are most recommendations for using boron fertilisers.

It is simply not true that boron is always immobile, phloem mobility varies widely between different crop species, varieties, and even in the same plant according to growing conditions.

Throwing light on how it behaves in different crops can teach us lessons about how and when to use boron for maximum effect on the crop, and how to create better products for farmers.

How do tomatoes and peppers take up and move boron?

If we study the path of boron through the plant, we find that it is a two-stage process in tomato and pepper crops. Boron is taken up from the soil and transported via xylem with water to foliage (see below schematic).

This process is controlled by transporter proteins that load the xylem, and how good they are at it varies between varieties. Some varieties are inherently better at this than others.

This means that boron movement from the soil is always to foliage, and not directly to the developing fruit and flowers. It also means that increasing boron in the soil does not directly lead to an increase in speed of transport to leaves, some varieties are better at it than others.

Once in the leaf, it has been established that both tomato and pepper crops are capable of translocating boron from the leaf to developing flowers and fruit. Boron moves alongside carbohydrates through the phloem, but the exact mechanism is still not known.

The limiting factor is not how much boron is in the leaf, but rather how fast the plant can link it to carbohydrates and move it through phloem. It is improving this process that can impact tomato and pepper fruit development.

Again simply applying foliar boron will not on its own improve the process, indeed applying too much will lead to toxicity. Better to use smaller amounts but get them moving from leaf to fruit more efficiently.

There are three factors at play when researching how to improve the movement of boron and translocation of carbohydrates from foliage to tomato and pepper fruit:

  1. Adequate boron levels
  2. Good photosynthesis
  3. Fast metabolism

Boron levels in foliage need to be good enough, but not too much. Throwing too much into the soil can lead to overdose. It is also subject to leaching so placing enough but not too much can be tricky. Leaf tissue tests only really tell you what is going on in the leaf (chronic deficiency) but not local deficiency (caused by transport).

Photosynthesis is important because it generates the carbohydrates that move to developing fruit alongside boron. Boron is involved in this process, and results from using boron are better when photosynthetic output is high.

Metabolism is the place where real gains can be made in the improvement of boron fertilisers. If the plants can quickly incorporate boron into the intermediate compounds used to move it to fruit then the flow is quicker and results improve.

If we increase boron levels without also addressing photosynthesis and metabolism its effect on flower and fruit development are limited. It just builds mainly in leaves with limited effect on fruit development.

Damu is a more advanced boron fertiliser

Damu is a new generation boron fertiliser developed by Levity Crop Science. Alongside boron, it contains Levity’s unique ‘Catalyst’ chemistry that improves photosynthesis and plant metabolism. It can be used to improve the speed at which boron and photosynthates are transported from foliage to developing flowers and fruit in tomato and pepper crops.

Research shows that Damu gives better fruit size than conventional boron fertiliser.

This data is from a replicated trial on a commercial bell pepper crop (variety Canon) in Spain comparing standard foliar boron with Damu. The standard product was applied three times at 1L/Ha and compared with Damu applied once at 2L/Ha 6 days before harvest.

We can see that supplying boron alone has an effect on fruit size, but Damu has a significantly greater effect. Damu increased average fruit weight, leading to a significantly larger yield.

Here we see peppers from a field trial in China, Damu treated plots produced significantly larger average fruit size.
Here we have the same effect on tomatoes in another field trial (also in China).

For best results on tomato and pepper crops foliar apply Damu at 2 L/Ha a week ahead of each pick.

Albina Fertiliser Bottle

Please contact us for more information about purchasing Damu.

Share this post:


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