hardening off issue - help

[swilder]

I have 220 vines of cab sav and cab franc located in between oakland and walnut creek california in highly clay soil. On a hill so working the soil gives way to too much erosion. This year before veraison my vines started yellowing from the bottom up usually starting around the perimeter of the leaves, anybody have a clue? at first I thought it was a watering issue but now i am thinking mineral deficiency.what do you think, any clues?

click on the link below for a closeup.

http://i1239.photobucket.com/albums/ff505/swilder1/canopyj-1.jpg

 

[M1wino]

I could be way off here but I've heard of something similar in blueberries here in Michigan and its caused by an iron deficiency. If the ph is too high or the soils compact such as clay it's hard for the plant to process iron. I don't know if this helps hopefully someone else will have some ideas too.

 

[grapeman]

Sorry I forgot to answer this the other day when I first saw your post.

It does look like a mineral deficiency. If the vines are all like this then I would do a petiole analysis to see which minerals are low. You could also check the soil pH for a low reading (acidic). The tests will tell you what to use. Instead of that, you could use the shotgun approach and hope you supply what is missing. Get a general purpose liquid fertilizer with micronutrients in it and spray on the leaves in a diluted amount as approved on the label. That will straighten it around for you.