michael wrote:

> On 19 Sep, 10:58, "Paul E. Lehmann" > wrote:
>> 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. Â*Potash (potassium) and magnesium are the most
>> > common. Â*Magnesium can be easily supplied with a few spoonfuls of
>> > Epsom salts. Â*I read the other day that grapes usually don't need
>> > added phosphates. Â*http://www.honeycreek.us/leaf_chart.php
>>
>> > You hit the nail on the head about the benefit of mulch. Â*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
>>
>> It was probably the long warm, dry spell that made the vines healthy.
>> Vines love and thrive in those conditions.
>>
>> I don't think Michael lives in a semi-arid part of the world requiring
>> mulch.- Hide quoted text -
>>
>> - Show quoted text -
>
> Hi Paul,
> Although I do not live in a semi-arid part of the world,my
> sloping dry limestone south facing soil does dry extremely quickly
> during the summer.The grass on the adjoining orchard becomes a pale
> straw colour for a couple of months,and the planting of fruit trees in
> the orchard is almost impossible without regular watering in the first
> couple of years.So it may be the case that mulching in March helped
> the vines over the very warm dry June period,and stopped any powdery
> mildew developing.

If you had a sunnier and warmer season than usual thus far, that could be
the major reason for lack of powdery.

> In other years,I have some powdery mildew,even
> though I spray regularly with wettable sulphur.This year I have not
> detected any powdery mildew on any of my four varieties of
> vines.So,maybe the jury is still out as to whether the mulching has
> helped the vines in my particular situation,but I am tempted to mulch
> again next year.
> Best regards
> Michael

How many rows do you have?
Could you do an experiment and mulch some and don't mulch others and see if
there is a difference?