Background: deficiency and toxicity
- Boron deficiency is most likely to occur on irrigated soils with a high pH.
- Boron deficiency may also occur on some free draining soils, particularly if soil is dry early in the season.
- Deficiency symptoms include death or stunting of the growing points, internodes are short and the plant has a stunted, bushy appearance. The leaves also thicken and the margins roll upwards.
- Most U.K. soils may be expected to provide sufficient boron for potato crops, provided that availability is not restricted by dry soil.
- There is a narrow optimum concentration of boron in potato tissue: sufficient levels are usually between 25 – 80 ppm (early season) or 25 – 50 ppm (plants>30 cm high).
- Boron toxicity results in blackening of stems and in necrosis and death of the lower leaf edges.
Application of boron
- Ensure that soil is well structured, to allow rapid root growth.
- Ensure that soil nutrients are sufficient when roots are growing, apply water if necessary to ensure uptake.
- On soils where boron deficiency may be expected, analyse concentration in foliage early in the season.
- If the concentration is low (< 30 ppm), make a foliar application of 150 – 300 g B ha-1 after emergence, to achieve a concentration of 30 – 40 ppm in foliage.
- Check concentration of boron in tissue.
- If necessary (i.e. < 30 ppm), apply a further 150 – 300 g B ha-1.
- Boron is not mobile in the phloem of potatoes, so repeat applications may be required.
Micro-nutrients 2001 (Includes boron physiology summary)
Boron nutrition 1996 (Physiology and requirements)