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 charged 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 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 over the past four seasons in wheat crops with an average of 70% of wheat samples received at Lancrop Laboratories being deficient in boron.
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 a 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/affect calcium absorption, so supplies are important to ensure balanced nutrition. Boron is relatively immobile within the plant so younger leaves and tissues will be affected first.
Treat boron deficiencies with foliar applications
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.
Independently managed Yara trials have shown that splitting YaraVita Bortrac applications at T1 and T2 gives a higher yield response than applying it at the traditional later timing.
YaraVita Bortrac contains 150 g/l boron as a fully soluble liquid and should be applied at the rate of 1.0 l/ha if one application or split into two applications at 0.5 l/ha (giving 150g boron per ha).
The following foliar micronutrients are recommended for cereals to prevent or correct boron deficiency
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