In table grape production, boron is a small nutrient with a big impact. Although required in tiny amounts, it plays a crucial role in yield, fruit quality, pollination and overall vine performance. An Agronomist at Yara Africa Fertilizer, Pieter Botha, explained that boron and zinc are the two micronutrients grapes require most, largely because of their influence on growth, fruit set and berry development. While annual boron use typically ranges between 150g/ha and 300g/ha, requirements differ according to soil, cultivar, planting density, canopy size and vine vigour.
Boron contributes to enzyme function, sugar movement, hormone synthesis and maintaining cell structure. It is concentrated in actively growing tissues, where it improves cell wall elasticity, supports flower development, assists with calcium transport and is vital for pollen germination and fruit set. Without sufficient boron, vines struggle to convert flowers into berries, leading to fewer, smaller fruit and uneven bunches. Because boron becomes fixed once inside plant tissues, it is immobile and deficiency symptoms appear first in young leaves.
Foliar applications offer a fast and efficient way to correct shortages, while soil applications are important in naturally low-boron soils especially sandy or sandy-loam types. The nutrient is most critical just before and immediately after flowering to ensure good pollination and a full berry set. Postharvest sprays help rebuild reserves for the following season. Application rates vary by product and must be guided by soil and leaf analyses. For example, YaraVita Bortrac 150 is usually applied between 0,5ℓ/ha and 1,5ℓ/ha, while YaraLiva Nitrabor offers a soil-applied option containing nitrate, calcium and boron for early-season use when roots are most active.
Symptoms of boron deficiency often appear soon after bud break and may include retarded shoot growth, shortened internodes, zigzag shoot formation and dwarfed lateral shoots. Later in the season, vines show poor berry set and uneven bunches, commonly known as “hen and chickens”, which reduces uniformity and market value. To manage levels effectively, Yara recommends leaf sampling at fruit set and veraison, noting that leaf blade analysis is more reliable than petiole testing.
Botha noted that foliar applications are usually the most effective delivery method for micronutrients, though soil treatments remain essential in boron-deficient soils. Research from California shows that repeated annual soil applications can correct severe shortages over time. In fertigation systems, boron is often included unless existing levels are already high. Boron toxicity, though rare, may occur in soils with unusually high concentrations, showing as necrotic leaf spots followed by yellowing and leaf death. In such cases, Yara advises improving drainage and increasing organic matter to help leach excess boron.
Given that the cost of producing table grapes now exceeds R400 000/ha, Botha warns that skipping boron is financially risky. Even when levels appear sufficient, one or two routine foliar sprays are advised as part of a comprehensive nutrient programme. Boron shortages are especially common in sandy, low-organic soils near river basins, which also have low clay content and poor nutrient-holding capacity. Soil pH strongly influences availability, with boron limited at pH levels below 4,5 and above 8,0. The optimal pH is around 6,5 and growers can adjust through liming or careful use of acidifying fertilisers.
Although boron is needed in small quantities, its effect on production is significant. By supporting pollination, berry formation, fruit size and uniform ripening, it remains one of the most important micronutrients in table grape farming. As Botha emphasised, a well-planned boron programme guided by soil and leaf analysis helps farmers secure consistent yields, high fruit quality, and healthier vines throughout the season.
