New research from the National Wine and Grape Industry Centre (NWGIC) has an important message for growers using tissue analysis to estimate the nutrient requirements of their vines – use the whole petiole.
The research by NSW Department of Primary Industries (DPI) principal research scientist Dr Suzy Rogiers and Charles Sturt University (Charles Sturt) postdoctoral research fellow Dr Tintu Baby has found significant differences in the nutrient status of different parts of the petiole, or leaf stalk.
“Vine nutrition is a key element of vineyard management and can impact on vine growth, crop yield, berry composition, and wine quality. Petiole mineral analysis is an important tool for determining vine nutritional status.” Dr Baby said.
“The current guidelines for petiole analysis recommend collecting samples from opposite bunches at 80 per cent flowering with a representative sample of at least 100. Our research has also shown it’s also important to collect the whole petiole, as the results can vary in the leaf stalk.”
The researchers analysed more than a thousand samples collected at flowering across three varieties, Cabernet Sauvignon, Shiraz, and Chardonnay.
Dr Rogiers said the same number of samples were also collected at veraison
“We looked at three petiole segments, and compared them with the leaf blade and the bunch stem,” Dr Rogiers said.
“We also assessed the nutrient levels in the leaf opposite the lower and upper inflorescence on the shoot.
“The study found the level of most elements were lower in the middle, narrow portion of the petiole.
“We found more than a two-fold difference in the level of potassium, one of the major nutrients, between the middle portion of the petiole and the portion closer to the leaf. There was a 20 per cent difference in phosphorus between the portions.”
Key messages for growers:
1. When removing the petiole from the vine take the whole petiole and pinch off the blade as close as possible to the end of the petiole.
2. Be consistent in sampling the leaf across from either the lower or upper inflorescence on the shoot. Most of the nutrients are somewhat higher in the leaves opposite the lower (old) inflorescence, however for potassium the levels were higher in the leaves opposite the higher (younger) inflorescence.
The research is part of a Wine Australia-funded project that aims to optimise nutrient application to vines.
As part of the project the NWGIC researchers hope to make recommendations on how to refine tissue sampling protocols and to develop an app that will help with nutrient disorder identification in grapevines.
The NWGIC is an alliance between Charles Sturt, the NSW DPI and the NSW Wine Industry Association.