A post (Kefir & Yogurt for Early Blight of July 2, 09) digressed into using Kefir on the soil.

Erythritol, a storage compound, is found in plants. To make erythritol as series of steps occur which eventually rely on the enzyme erythrose reductase (E.R.). This can occur in an optimal pH of around 7, but a range of 6 - 8 pH works (such as in most gardener's soil).

Torula is an extensive yeast family, the Torula Kefir strain included. There are torula yeast with the E.R. enzyme & possibly the kefir strain has it too. Yeasts like temperatures of 25*C./77*F. - 35*C./95*F. for activity ( but can take 20*C. - 40*C.)

If there is a benefit from incorporating kefir curds into the root zone of a plant it is most likely in bulking up the root erythritol & making a robust root capacity for better functioning.

The other kefir yeast, Saccharomyces Kefir, also has enzymes. These type of enzymes allow re-organization of amino acid (protein building blocks) in compounds. A substitution of an amino acid can change the behavior of an enzyme & set in motion a different process. (No speculation on any specific benefit is being made.)

(As for the kefir's symbiotic bacteria: it is likely to degrade in the garden from the summer heat. So, not subject of this post.)

Copper definitely inhibits yeast (it is fungicidal), so kefir curds would need to be used at a different time for any beneficial affect.