Thursday, December 22, 2011

Phosphorous Deficiency in Grapevines

Phosphorous deficiency is an occasional problem for grapevines. Under natural conditions, almost all vines have a beneficial fungus, mycorrhizae, associated with their roots, which helps them to acquire P, but sometimes the soil itself prevents P uptake.

The distinct symptom of phosphorus deficiency is the appearance of discoloured, redden leaves.

Ben South has found this patch of vineyard over 'ironstone'. In acid soils P forms very insoluble compounds with iron, and it binds strongly to the surface of iron oxides.

Most soils used for viticulture in McLaren Vale have low native concentrations of phosphorus and therefore phosphorus fertiliser inputs are normally required. In this case the 'ironstone' has bound up all of the soluble phosphorous in the soil.

Phosphorus is taken up by vines from the soil water in its soluble phosphate form which would also be quickly bound up to the 'ironstone'.

Contact James Hook for more information.

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