Boron

An essential micronutrient, which is represented by the chemical symbol B. Boron is involved with the overall health and functioning of a plant, including cell division and being a component of cell walls, thereby aiding plant structure, although it isn’t a component of enzymes. It also aids seed development.

Boron deficiency has been identified as reducing leaf expansion and cell division (for both roots and shoots) thereby inhibiting growth. It can produce a wilted or distorted appearance to a leaf and it might also contribute to the disruption of cell wall structure. A visual symptom of deficiency can also be interveinal chlorosis.

It is unlikely that this micro-nutrient would need to be applied as a specific supplementary feed to turfgrass situations where clippings are removed in the UK because annual rainfall alone should meet this need. Irrigation water, top-dressing and fertiliser ‘impurities’ will also add additional amounts.

[Comment based on the follow calculations: If annual rainfall is given as a low average of 1000mm, for 1m² this equates to 1m³ (1,000 litres x 1,000,000,000 nanolitres) of water. If rainwater contains an average of 10ppb (or 10 nanolitres per litre, as 1 nanolitre is one billionth of a litre) of boron this then equates to some 10,000 nanolitres of boron per m²: this is 10ppm, which is a typical quantity in leaf dry matter and ‘only’ 5ppm might be removed per year where clippings are removed - based on 5,000kg/ha clippings removed, which may be relatively high for many situations. [Source: Park, H., and W. H. Schlesinger, Global biogeochemical cycle of boron, Global Biogeochem. Cycles, 16(4), 1072, doi:10.1029/2001GB001766, 2002, https://www.researchgate.net/publication/259265068_Global_biochemical_cycle_of_boron accessed 11th December 2023]

Excessive concentrations of boron are toxic to plant growth, with symptoms appearing as leaf tip die back, along with reduced sward health and performance.