Manganese in export wine - Q&A - Does this affect what we do in the vineyard?
On 27 February, Wine Australia released a warning to wine exporters regarding the increased scrutiny of manganese, iron and copper levels in wine by Chinese authorities.
Maximum regulatory levels now being imposed by Chinese authorities are 2 mg/lt for manganese, 1 mg/lt for copper and 8 mg/lt for iron. Wine Australia have recommended that all wine intended for export to China should undergo analysis to confirm that it complies with these limits.
Chinese law controls the amount of manganese that can be added to wine, however Australians don't add any manganese to their wine, neither do winemakers in other traditional wine producing countries. Manganese is a natural element present in soil. We do common apply manganese to grapevines as a trace nutrient. The rates of application per hectare are extremely low compared to the regulatory limits. For context a level of 2mg/lt in wine is equal to 2 ppm.
One application of a 10% strength manganese foilar fertilizer @ 2.5lt/ha applies 0.25kg/Mn/ha. If 100% of this manganese is taken in to the vine and then into the fruit (this is unlikely as fertiliser would also be converted into plant tissue, and/or lost to the soil etc. but for hypothetical reasons lets run with it) and each hectare of vines grew 10,000kg (10 tonne), then turned into 7,000 lts, this would give us the following equation.
0.25mg Mn in 7,000lts = 0.035mg Mn in 1,000lts.
0.035mg in 1,000lts equals 0.00035mg/L of Mn or 0.00035ppm.
With this rough equation we would have to apply our foliar fertiliser 2,800 times per season and have 100% efficiency into the fruit to increase the resulting wine 1.0mg/lt.
Make sense? Trace element applications are exactly that, only a trace.
Manganese in export wine - Does this affect what we do in the vineyard?
The short answer is no, DJ's recommend continuing to apply manganese to your vines if you have a demonstrable need. If you have any doubts over the level of manganese in your grape juice or the resultant wine consider contacting the AWRI which can test for manganese levels.