Boron is generally an overlooked micronutrient; it is often thought that only brassicas have a boron requirement and wrongly assumed to be less important for cereals and other crops in the rotation, however it is essential for all crops although brassicas have the highest boron requirement.
Given a wet winter and cold spring boron deficiencies are not too surprising
Boron like nitrate and sulphate exists in the soil as a negatively changed anion and like these other two nutrients is also readily leached, particularly from sandy soils with low cation exchange capacity. This leaching also makes it difficult to build up boron levels in the soil. Also like nitrate, boron moves into the plant is mainly by mass flow and diffusion so uptake is reduced in low temperatures as root growth slows and transpiration is reduced.
Widespread boron deficiencies have been seen so far this season in wheat crops with 91% of wheat samples received at Lancrop Laboratories being deficient in boron with 48% classified very low. This figure is significantly higher than in previous years where only around 20% were classified as very low.
Boron is needed for the production of nucleic acid and plant hormones and is typically found in large quantities in the leaves and growing points. Boron is important for pollen germination so deficiency can lead to poor fertilisation, reduced seed set and consequent yield losses. It is also involved in cell wall formation and lignification and so helps to increase cell wall strength which can help improve and also affects calcium absorption, so supplies are important to ensure a balanced nutrition. Boron is relatively immobile within the plant so younger leaves and tissues will be affected first.
Foliar applications of boron can be used to correct deficiencies if tissue results are showing low or very low levels and in deficient situations will protect the investment in the crop.
YaraVita Bortrac contains 150 g/l boron as a fully soluble liquid and can be applied to wheat right up to the end of booting GS49 at the rate of 0.5 l/ha (75g boron per ha).
The following foliar micronutrients are recommended for cereals to prevent or correct boron deficiency