B is for bulking

Using Boron to increase potato yield
Boron is the most variable of all plant nutrients in terms of how it is transported and metabolised by different plant species – because of this response to Boron can be highly variable.

Boric acid, the main form in which plants take up boron from soils is not phloem mobile, but some plant species can translocate it in phloem by forming complexes with sugars.

This is species dependent, as it is determined by what kind of sugars the plant synthesises. This means that the way boron functions is crop specific, what works on one crop will not necessarily work on another.

To improve yield on potatoes using Boron we need to understand:

1.  How Boron effects hormones.

2.  How boron effects carbohydrate transport.

Boron status alters hormone synthesis – changing where the plant grows

Potatoes are a crop where growers must balance top growth with tuber development to ensure good yield. The main driver in vegetative growth is nitrogen, whereby as nitrate levels increase the plant produces higher levels of auxin – leading to faster vegetative growth at the expense of tuber development. Farmers must carefully balance this nitrogen response to ensure top growth does not create problems with tuber yield and quality.

Boron deficiency in potatoes is more associated with rapid growth induced by growing conditions or nitrogen fertilization, than lack of supply from the soil. The more nitrogen the plant gets the faster it grows and the more deficient it becomes in B. Meaning that even in soils with good levels of B you can get leaf deficiency of boron during periods of rapid growth.

Research from the Liebniz institute in Germany shows that boron status has a marked effect on relative production of plant growth hormones. Plants deficient in boron make higher levels of auxins and lower levels of cytokinins and gibberellins, as boron levels increase this reverses with auxins decreasing and cytokinins increasing and becoming more active.
As plants start to increase pace of growth under the influence of N, if boron levels do not keep up auxin synthesis gets out of control. This starts to effect where the plant grows, increasing the ‘nitrate effect’ and reducing tuber development at the expense of vegetative growth (see illustration below).
When leaf boron status is high the opposite effects are seen on plant hormone synthesis, whereby auxins decrease and take less active forms, and cytokinins increase and take more active forms. Gibberellins also increase where boron status is high (see illustration below). This gives a greater focus to root and tuber development by the crop.
Boron can be used to reduce auxin synthesis and slow down periods of rapid vegetative growth. Timing and quantity have to be right for this, as there is a fine line between deficiency and toxicity with boron. This means choice of product, timing and placement are vital.

Levity have developed Damu, a high efficiency product that allows lower rates of B to be more effective, using stimulants to increase speed of uptake and metabolism. Damu can be used during periods of excess vegetative growth to reduce auxin production and refocus the crop on root growth.

Boron influences carbohydrate transport to tubers

When leaf boron status is high the opposite effects are seen on plant hormone synthesis, whereby auxins decrease and take less active forms, and cytokinins increase and take more active forms. Gibberellins also increase where boron status is high (see illustration below). This gives a greater focus to root and tuber development by the crop.

To develop tubers the potato plants move sucrose from photosynthesising leaves (where it is created), to the tubers (where it is converted to starch and stored). Boron also plays a role in this movement of sucrose from leaves to roots and so has a key influence on tuber bulking.

Boron is not as a nutrient phloem mobile, it is taken up and moved passively upwards through the plant with water accumulating mainly in leaves. During bulking potatoes translocate sucrose from leaves to tubers using bis-sucrose-borate, a phloem mobile complex formed between boron and sucrose.
Damu helps to facilitate bulking by improving translocation of sucrose to tubers for starch formation. 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.

How to use Damu on potatoes

Boron has a role to play in preventing rapid vegetative growth reducing tuber development, and in improving bulking via improved carbohydrate transfer to tubers. Damu is a unique formula developed by Levity Crop Science, proven to improve tuber size in potato crops.  It can be used a a low rate in during the bulking period to maintain proper tuber development during periods of rapid growth, or at a higher rate ahead of harvest to bulk tubers.