Minimal Imput Viticulture.
The credentials of organic and biodynamic viticulture are well documented, however, d’Arenberg Chief Winemaker and Viticulturist, Chester Osborn believes the benefits, both environmentally and to grape quality, of minimal input (mi) grape growing deserve wider recognition. The essence of the philosophy is minimal or no irrigation, no fertilization, minimal spraying and no soil cultivation. These practices are employed across vineyards owned, leased and contracted to d’Arenberg to ensure grape quality and environmental responsibility.
"With minimal irrigation and no fertilization the vines develop strong root systems that penetrate deeper into the soil profile and spread wider giving the grapes a greater expression of the soil," Chester explains. "When we stopped fertilizing we noticed that skins were getting thicker with a lot less green tannins and the berries were more turgid with better acidity and they were ripening at lower sugar levels."
Driven by the greater levels of flavour,
"The further a vine moves away from fertilization the less irrigation it needs because it develops a much stronger root system, making dry growing a lot more viable for many of our vineyards.
"A vine generally only absorbs about 45% of the nitrogen in fertilizer. Micronutrients are the opposite charge to many nitrogenous fertilizers and stick to them, this causes a problem when it rains as it effectively leeches the soil as water moves through. This is obviously not good for the long term sustainability of the soil or grape quality. "If you’re not fertilizing the nitrogen in the soil is very low which forces the vine to develop stronger enzyme activity to produce its own nitrogen based compounds which I believe has an impact on the vine’s ripening behaviour."
Many d’Arenberg vineyards are completely dry grown, and those irrigated only receive strategic drip irrigation at two possible times, and only if required. The first time is before flowering in winter or early spring and only in dry years. This emulates rainfall and promotes healthy canopy development and ensures bud burst. The second time is at the end of December to ensure irrigation is not needed during ripening.
"Once we stopped cultivating and fertilizing we noticed the water holding capacity of the soil improved and the vine’s roots became more active in the mid row with more micronutrient uptake. With less water the deep roots also began to develop." The net effect of minimal input viticulture is slightly lower yielding vines producing intense flavoured grapes showing the individual character of the soils they are grown in. The environmental benefits are also significant with less mechanical requirements, less water and soil richer in natural micronutrients.