On Sep 19, 4:02 am, michael > wrote:
> On 19 Sep, 03:26, shbailey > wrote:
>
>
>
> > On Sep 18, 4:42 am, michael > wrote:
>
> > > I thought that I would try again to further my understanding of
> > > observations on my vines in England this year,based on the very useful
> > > replies and discussion.There will always be disagreement,but as
> > > someone new to growing grapevines,I hope that I can understand the
> > > issues.I apologise to doubi..for my recent comment,and hope that he
> > > can continue to help.
> > > Let me try again to summarise my recently gained knowledge:
> > > 1)Using wood chip as a mulch on the surface around the vine can
> > > greatly help in the stabilisation of upper soil moisture content,and
> > > will not affect the nitrogen of the vines-rotovating or digging in
> > > wood chip will rob the soil,and this is my gardening experience.Garden
> > > compost could be even better,as it introduces a living worm population
> > > which may help soil texture.
> > > 2)Wasps or other insects are not the source of primary damage to
> > > ripening grapes,but can spread the rot to other grapes in the bunch.A
> > > primary source of damage could be a heavy rain shower,causing
> > > splitting,followed by wasps,etc moving in.I think that this is what
> > > happens with plums after they split when nearing ripeness.My culling
> > > of the majority of the wasp population will still help,I believe.
> > > 3)I thought that darker vine leaves to be an indicator of too much
> > > nitrogen.I would like to know what the indicators are for vines
> > > needing more phosphates,or potash,so that I know what fertiliser to
> > > add to my compost.
> > > 4)One indisputable fact is that my vines and grapes are sofar much
> > > healthier this year. I believe that probably the main cause is the
> > > long very warm dry spell here in June-but I do not really know.It
> > > could be the compost keeping moisture levels stable.
> > > 5)My original post was about pruning of laterals or sideshoots for
> > > vigorous vines in a cool climate.My policy now is to remove most of
> > > them in June and July to prevent a dense canopy developing,thus
> > > encouraging powdery mildew,and then leave them alone after veraison to
> > > have maximum leaf for the ripening period.
>
> > > I hope that my understanding is improving and welcome your comments
>
> > > Michael
>
> > The following link provides pictures of grape leaves with various
> > nutrient deficiencies. Potash (potassium) and magnesium are the most
> > common. Magnesium can be easily supplied with a few spoonfuls of
> > Epsom salts. I read the other day that grapes usually don't need
> > added phosphates. http://www.honeycreek.us/leaf_chart.php
>
> > You hit the nail on the head about the benefit of mulch. If you had a
> > long warm, dry spell and your vines remained healthy, it was due to
> > the stable moisture levels enabled by your mulch.
>
> > Stephen- Hide quoted text -
>
> > - Show quoted text -
>
> Thanks for that,Stephen.I have two questions.
>
> 1)When my grapes are ripening,the lower leaves seem to die back
> naturally.Is this the time to look for mineral deficiencies
> e.g.potash,or at an earlier stage?
> 2)What are the symptoms of nitrogen deficiency or excess?
>
> Regards,Michael
Michael,
At this time of the year, the old leaf die back is natural. If it
occurs prior to veraison, it can be a sign of drought stress (which
can be lessened by the use of mulch). Drought stress may be manifest
by signs of nutrient deficiencies. If you get yellow/red/purple
streaks in your leaves prior to ripening time, it is nutrient
deficiencies showing up like in the pictures on the link.
Nitrogen needs are variety dependent to a degree. I have seen Merlot
described as a "nitrogen hog", meaning if it has a lot of available
nitrogen it will grow like crazy and not produce many grapes. If a
vine has rampant growth but little fruit production, it probably has
too much nitrogen. If it is a weak grower with small pale leaves, it
may benefit from a little extra nitrogen and other nutrients.
Stephen