3 June 2005
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Content:
Vineyard Fertilization
Captan Label Change
Phosphorous Acid Fungicides
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Vineyard Fertilization
By Dave Scurlock and Imed Dami, OARDC
It is nearing time to start applying fertilizer if you have not done
so already. In the past we would apply fertilizer in early spring before bud
break because we had some time before spring work really got started. We had
finished pruning, tightened the wires, tied up the vines, replanted missing
vines and removed our hills on the vinifera. Now what? Let’s throw on
some fertilizer and get that done so we can go on to some other operation.
Is timing of fertilization really that important? The following
excerpts are from an earlier report out of the Vineyard Vantage. A report by
Eric Hansen indicated that multiple applications of nitrogen may be needed to
maintain sufficient nitrogen in the root zone over the extended period of peak
demand, particularly on sandy soils. Efficiency of nitrogen uptake may also be
affected by fertilization placement and rate. Greatest absorption may be
achieved when fertilizer is applied over the soil containing the most grapevine
roots, which is normally the herbicide strip immediately under the trellis.
This is most important in younger vineyards where the root system is not as
extensive. As a general rule, the percentage of fertilizer nitrogen absorbed
decreases as the rate of nitrogen increases. Although some growers apply high
rates of nitrogen in a single application, greater efficiency of nitrogen uptake
may occur from multiple applications banded beneath the vine when the vine
demand is high. Studies have shown that application of nitrogen while grapes
are dormant is inefficient because a high percentage of the applied nitrogen is
leached from the soil before uptake by the vine. Vines absorb nitrogen
relatively slowly between budburst and bloom, most rapidly between bloom and
veraison and then slow down between veraison and harvest. Thus the most
efficient time to apply nitrogen would be shortly after bloom when the vines are
growing rapidly.
Application Rate: Generally we apply approximately 50 pounds of
actual nitrogen per acre each year to juice grapes with lower rates (30 pounds)
applied to wine grapes. The actual nitrogen that you apply is calculated
by taking the form of nitrogen that you are applying such as ammonium nitrate,
which is 33% nitrogen and multiply the weight of a 50-pound bag of ammonium
nitrate which will give you 16.5 pounds of actual N that you are applying
per bag. Approximately three 50-pound bags will give you 50 pounds of actual N
per acre if applied at 0.27 pounds of ammonium nitrate per vine at an 8 foot by
10 foot spacing (545 vines/acre). Example 2: Urea (45% N) x 50 lb bag of
Urea = 22.5 lbs of actual N/bag. If you are going for 50 lbs of
actual N per acre then:
50 lbs/acre divided by 22.5 lbs of actual N = 2.22 bags per acre using
Urea at the 50 lb per acre rate.
Training systems that permit large vines such as Geneva Double Curtain
(GDC) require higher application rates of 75-100 pounds of actual N per
acre. Larger amounts are best applied as split; half rate applied by bloom and
the second half by veraison. Younger vineyards require less nitrogen usually in
the 15 to 20 pounds of actual nitrogen per acre. Nitrogen is readily available
between the pH values of 6.0 and 8.0, but becomes less available at lower or
higher pH levels.
We would like to see pH values around 6.0 to 6.5. The American varieties can
tolerate lower pH values of 5.5 better than vinifera type grapes. Liming should
be done after you have tested your soil and determined a need and the absolute
best time to lime is well in advance of planting so that you can incorporate the
lime into the soil 8 to 12 inches deep. The pH is much more difficult to
correct after the planting because of the slow movement of the lime through the
soil. Lime can also increase the availability of other elements such as
phosphorus, calcium, magnesium, and molybdenum. The dolomitic lime can be used
to raise the magnesium content in the soil and pH and a calcitic lime can be
used to raise the calcium content as well as the pH in the soil. If the soil pH
was not corrected before planting the pH may be raised over time with multiple
applications of lime of 2 to 2.5 tons per acre twice a year.
Can Potassium additions help? Next to nitrogen we have to
consider Potassium as one of the next most important elements to maintain good
vine health and sugar development. Application rates should be based on vine
vigor, soil tests, and petiole analysis. For soil applications 100-400 pounds
per acre of 0-0-60 is recommended. The number of applications may be higher in
clay and sandy soil if the pH is above 6.5. Apply potassium in 2-foot bands
under the trellis to assure that the major portion of the material will be
available for root uptake. Potassium can be applied anytime, but the maximum
uptake will be between bud break and veraison and again immediately after fruit
harvest.
Organic fertilizer? Any time you can add organic material to the
fields it is going to help the health of the soil and tilth. An organic
material may vary greatly in composition depending on its source. When such a
material is applied as a fertilizer an unknown quantity of nitrogen, phosphorus,
potassium or other elements are applied unless it has been analyzed. Cost to
obtain and spread and amounts are usually higher unless a readily available
source is part of the operation. Observations of growth and petiole analysis
can tell you if you are getting enough nutrients to the vines. Organic materials
such as mulches can have a detrimental effect of tying up nitrogen that is used
by microorganisms to break down the mulch into a usable form for the vine.
Additional nitrogen to feed both the vine and microbes will alleviate this
problem.
What about fertilizing vines that were winter injured? The rule
here is wait and see. We are definitely going to want to reduce the normal
application rates of nitrogen to vines that are showing signs of winter injury.
That is delayed bud break or uneven budbreak and shoot growth. If you are
unsure about your crop, it might be advisable to split the nitrogen application
this year and apply a half-rate at bloom (two thirds of nitrogen goes to
vegetative growth, one third to fruit). If you have very few shoots, this may
be a year to not apply nitrogen. Watch for nitrogen deficiency symptoms (thin
weak growth, light green foliage). If symptoms develop, apply a foliar spray of
urea around veraison. Foliar sprays can be a corrective for deficiency
symptoms, but are not a permanent solution to vineyard fertility problems.
Captan Label Change
By Dr. Mike Ellis, OARDC
Fruit growers that use Captan fungicide are aware that several years ago the REI
(reentry interval) for all formulations of Captan was set at 4 days. This
created a problem for growers that needed to send workers into the planting
within the 4-day REI. In addition, brambles (raspberries and blackberries) were
removed from the label. A few years ago, the REI on strawberry was reduced from
4 days to 24 hours, but remained at 4 days for all other crops. About a year
ago, the 80WDG formulation of Captan from the company Mico-Flow obtained a
reduced REI for several fruit crops and brambles were added to the label. The
REI was reduced from 4 days to 24 hours for strawberries, almonds, apples
apricots, cherries , plums/ fresh and prune and peaches. The REI was reduced
from 4 to 3 days (72 hours) for blueberries, grapes, raspberries, blackberries
and dewberries .These changes were not made for the Captan 50 WP , Captan 80WP ,
and Captec 4L formulations.
I have just learned that the Drexel company has the new label (reduced REI and
brambles on the label ) for Captan 50WP , Captan 80WP , Captan 80WDG and Captan
4L. The Micro-Flow labels for the Captan 50WP, Captan 80 WP, and Captec 4l have
not been changed as of yet.
The bottom line is that if you want the reduced REI and brambles on the label,
and you want to use a formulation other than the 80WDG, you need to make sure
the material you buy is produced by Drexel. You also need to check the label
before you buy it to make sure it has the new label. Old material may still have
the old label. ALWAYS READ THE LABEL.
Another short note on Captan. I have heard from several growers that the Captan
80 WDG formulation foams badly. To prevent problems when filling, you should try
putting in the water then adding the Captan 80WDG. It will disperse into the
water and the agitator will mix it well. You can also use an anti foaming agent.
Contact Mike Ellis if you have questions. E-mail is
ellis.7@osu.edu and phone is 330-263-3849.
Phosphorous Acid Fungicides
By Dr. Mike Ellis, OARDC
The attached article, Phosphorous Acid Fungicides, provides some good
information about phosphorus acid fungicides. I believe that these materials are
an important addition to our grape fungicides for control of Downy Mildew. I
would like to thank Dr. Schilder for the use of this note.