gunner wrote:
"David Hare-Scott" wrote in message
"My zuccs have BER!"
"As I understand it the problem is due to deficiency of
calcium in the plant which can be brought about by uneven water
availability or lack of calcium in the soil.".
Absent more specifics, I believe that is more SWAG than fact.
Consider the chemical distribution of Ca w/in the plant.
Most likely your plant's available calcium is being diverted from the
fruit & going to the leaves where it is needed more at that
particular time, say for transpiration.
I am beginning to suspect that this is the case. We have had a rather warm
spring and these plants are putting on growth at a high rate.
Ca is not a mobile nutrient, i.e. going where it is best needed. If
BER occurs when temps are high, try slowing the plant's transpiration
rate to get a better Ca distribution. Note, even if you have
adequate soil Ca, its uptake can be limited by other factors such as
listed in the Spectrum Analytic article* below . If BER is a
constant problem, try the preventive measure outlined in the ISHS abstract
** below.
The soil has been amended with lime and gypsum.
They are growing strongly with a multitude of flowers and fruit
setting. One odd thing is that normally this strikes on the fruit
when they are quite small but this time they are getting nearly to
cutting size before it starts.
I'm curious; did a soil analysis/test indicate you needed the lime and
gypsum or is this just a gardening "best practice" method?
I have not had a soil analysis done as I don't see the need. I grow a very
wide range of fruits and veges quite successfully and I see no signs of
consistent problems which would lead me think the soil has deficiencies. I
have done pH tests myself using a dye indicator system which I believe to be
reliable and accurate enough for the purpose.
If you care to share; what type is your soil, pH, amendment regime,
fert/schedule, etc.?
The soil profile is about 20cm of nearly black silt over plastic smectite
clay (which I don't disturb). The silt is somewhat friable but has quite a
bit of clay and without amendment still clumps together to a degree when
wet. The starting pH is 5.5 and I have been bringing it up over time with
lime, it is about 6 to 6.5 now so I don't add lime as a rule now. When I
established the plot 4 years ago I added gypsum to help break up the clay.
I add chicken litter, horse manure, a touch of soluble potash and compost
every year and mulch with hay which gets incorporated. I add a seaweed
extract every two years. The citrus get a soluble trace element mix when
they need it. - about every three years.
The result is after 4 years the vege plot is much more friable and now has a
good infiltration rate, for a clay-based soil it is very good. Given the
clay and organic matter in the soil the TEC (and CEC) would be quite high
but I haven't measured it. I see no signs of nutrient runoff downhill.
There is no limestone or sodised soil around the area and the river water I
use to irrigate has an EC which varies with rainfall but is typically around
200-300 microsiemens/m. I use raised beds which gives drainage and about
40cm of depth.
The average annual rainfall is about 1100mm but the fall is extremely
erratic which is a potential problem. We have not had prolonged rain since
the summer veges were planted. However, the clay subsoil acts a sponge
soaking up water during rain and the releasing it in between times, to
illustrate, it is two months since we had significant rain, and five weeks
since anything useful in the rain gauge at all and in the last month we have
had record temperatures for the month up to 41C. Yet my pasture is green and
growing very strongly without irrigation. I have been monitoring the veges
and fruit trees and irrigating them as required.
So to summarise, I see no cause for calcium problems except the zuccs are
growing too fast for their own good.
"Any ideas from experience?"
"Any references to a detailed explanation of how BER happens..."
Try these:
* http://www.spectrumanalytic.com/supp.../Ca_Basics.htm
** http://www.actahort.org/members/show...knrarnr=145_23
http://www.springerlink.com/content/ww87lw2086rj3v71/
http://jxb.oxfordjournals.org/cgi/co...tract/44/2/509
General reads on BER:
http://pubs.caes.uga.edu/caespubs/ho...ossom-rot.html
http://wihort.uwex.edu/fruitveggies/TomatoDisorders.htm
thanks for the refs
David