marquette nutrient defiency or fungus

[wood1954]

I planted my Marquette grapes 4 years ago in sandy soil. The soil test result indicated I needed potassium and phosphorous I put about a 1/4 cup around each plant in the spring of 10-10-10 fertilizer and things went well lots of growth and then the vines seemed to pause and two got very pale green almost yellow and this one plant has either N or FE deficiency. So, a couple questions, first what deficiency do they have and or is it that or fungus, if deficiency can I fertilze this late in the summer? I think the first photo is potassium def. the smaller pic is either N or FE and the plant has been struggling it's entire life.
also on another topic, these grapes put out some 10-12' bull canes that I cut back to midway between plants, my plantings are about 8' apart. was that a mistake or not. Thanks

 

[ibglowin]

You in WI right? Hard to believe but looks like your pH in the soil is off which effects the vines ability to properly take up and convert nutrients (photosynthesis) Usually something with ferrous sulfate is applied which lowers the pH in the soil and then things return to normal. I have had good luck with anything with ferrous sulfate on the label.

 

[BigH]

I vote Iron Chlorosis or Nitrogen deficiency. Potassium deficiency would present as orange/brown discoloring of leaves. Since you had bull canes, Nitrogen deficiency seems a little less likely. Iron problems usually appear in young leaves first.

What was the pH from your soil test? Has it been excessively dry or wet there? Nitrogen is highly mobile in soil when water is present. If your soil test pH was below 6.5, then I would consider hitting these with a fertilizer that is heavy on Nitrogen, such as 28,0,3, and then watering that in. This is not normally a good time of year to apply Nitrogen, but you may not have a choice. You might want to give them a shot of water if it has been really dry. That may allow the plant to take up some nutrients that are already there. If it has been crazy wet, then you can lose nitrogen to leeching. Not much you can do about that other than fertilizing and letting it soak in.

Plan on getting a new soil test this fall if you haven't done one since you planted the vines.

H

 

[wood1954]

I decided to pay the $40 and have a petiole analysis done then I'll know for sure.

 

[Masbustelo]

Let us know the results

 

[wood1954]

So here they are, results from the lab only took a day to get. It looks like my soil is high in P and K and Mn. Everything else is borderline or low. I think. I spent a good amount of time searching the web for how to interpret these results. the scribbling on the test sheet is mine. according to my reading i should do this test again at bloom. My vine that was suffering so much had to be put down. When I cut the trunk it was almost dry, seems like a fungal infection in the trunk. Weird tho I took 4 lbs of grapes from her that were sweet, the rest of my plants are still very sour. so I also found a great site for tissue analysis and fertilizer ..https://www.prairiefirewinery.com/Cellar/wp-content/uploads/2016/12/Fertilizer-mgmt.2013-KS.pdf, this winery has a lot of articles etc under the Learn heading on their website. hope this helps other growers.

 

[Masbustelo]

Do you know the classification of your soil? What kind of agriculture was it used for if any?

 

[wood1954]

In the past prior to WW2 it was pasture, about that time it was allowed to go wild. Lots of hardwoods grew up and I removed them and their rootball when I put in my grapes. The soil is around ph 6.5-7.0 sandy loam. I used a cheap soil ph meter and tested the soil close to each vine and found 6 or so with low ph, 5.0 to 5.5. not being very bright I had been putting fertilizer in a circle around the trunk and it seems I overdid a few of the vines as the ph 2' away from the trunks is 6.5-7.0. so now I know not to do that. The one that died had soil at 5.0 and when I went to remove it the roots had traveled out at least 3 or more feet from the trunk, so now when I need to amend the soil I'll use a broadcast spreader as the roots have really grown out. there is a lot to learn to this grape growing, it was so easy when I just went to the liquor store..