As shown in the table below, nitrogen is an essential element in the growth of grape vines and an imbalance in its levels can lead to problems in the vineyard and/or in the winery.
|Nitrogen and grape vines (Compiled from Grande Passione -- Soil minerals vs wine quality)|
According to Schwarcz and Schoeninger (Stable Isotope Analysis in Human Nutrition, Yearbook of Physical Anthropology 34, pp. 293-321), almost 100% of exchangeable nitrogen is found in the atmosphere or dissolved in the world's oceans and is transferred from these environments into the biological system through the processes illustrated in the figure below. The commonly held view is that grape vine plants receive their nitrogen through the terrestrial nitrogen cycle but the Morford study calls this into question.
Nitrogen, as is the case for all plant nutrients, is sourced from the soil by the plant. According to Christopher Bargman (Geology and wine in South Africa, Geoscientist 15(4), April 2005), soil is the major influence on the growth of the vine plant as it provides: (i) a supply of water; (ii) anchorage in the ground; and (iii) a source of nutrition. The classic soil profile is shown below.
The authors studied the nitrogen content of soils and forest foliage in forests that were underlain by both sedimentary and igneous bedrock and found the following: (i) the nitrogen content in soils and foliage that grow above sedimentary bedrock is 50% higher than soils and foliage that grow over igneous bedrock; (ii) nitrogen isotope values for rock, soils, and plants are indistinguishable among each other when located above a nitrogen-rich sedimentary bedrock but that is not the case for the same elements overlaying an igneous bedrock; and (iii) "forest responses to geological N inputs are manifested as higher foliar biomass production ..."
The authors conclude that "Our results raise the possibility that rock weathering may be a significant source of N to terrestrial ecosystems..." underlain by terrestrial bedrock.
I compiled the following table of wine regions that may and may not have benefited from the phenomenon described by the authors. The table shows that some of the world's foremost wine regions are underlain by sedimentary bedrock and may have benefited from that "siteing.".
Additional study will be required to determine the benefits and disadvantages associated with subterranean nitrogen, the implications, and what, if anything, should be done to maximize its effects and minimize its disadvantages. The information provided herein could be of benefit in making decisions regarding vineyard locations or vineyard retention in the case of a vine-uprooting program.