I UNIVERSITY OF FLORIDA 1
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INSTITUTE OF FOOD AND
UNIVERSITY OF FLORIDA
A Vegetable Crops Extension Publication
Horticultural Sciences Department P.O. 110690 Gainesville, FL 32611 Telephone 392-2134
June 16, 1993
I. NOTES OF INTEREST
A. Vegetable Crops Calendar.
B. Steve Sargent to go on Faculty Developmental Leave.
A. Tipburn and Internal Rot in Chinese Cabbage.
III. VEGETABLE GARDENING
A. Organic Gardening Research and Education Park.
Note: Anyone is free to use the information in this newsletter.
Whenever possible, please give credit to the authors. The purpose
of trade names in this publication is solely for the purpose of
providing information and does not necessarily constitute a
recommendation of the product.
The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research, educational
information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS, STATE OF FLORIDA, IFAS, UNIVERSITY OF FLORIDA,
U.S. DEPARTMENT OF AGRICULTURE, AND BOARDS OF COUNTY COMMISSIONERS COOPERATING.
I. NOTES OF INTEREST
A. Vegetable Crops Calendar.
July 27-30, 1993. State 4H Club
Congress. Includes State Horticultural
Judging/ID and Demonstrations, plus
horticultural workshop. Gainesville.
(Contact Jim Stephens).
B. Steve Sargent to go on Faculty
I have accepted an invitation by a
Brazilian government research center to
spend the next year working with
colleagues in the area of postharvest
technology. I will be on Faculty
Development Leave from July 9, 1993 to
June 30, 1994. During this period we plan
to document postharvest losses in fresh
commodities during handling from farm to
consumer in the greater Rio de Janeiro
region. This information will permit
development of feasibility studies to
determine the level of technology which
might be implemented in order to reduce
losses estimated from 30 to 50%. I will
also be developing collaborative research
projects with other postharvest researchers
in Brazil on problems of mutual interest
related to handling of tropical and sub-
In my absence, Dr. Mike Talbot
(Agricultural Engineering Department)
has agreed to handle questions regarding
postharvest handling problems. Dr.
Talbot's phone number is 904-392-9164
(Sargent, Vegetarian 93-06)
II. COMMERCIAL VEGETABLES
A. Tipburn and Internal Rot in
This seems to be the year for
problems in Chinese cabbage. You may
remember the pepper spot article in the
March Vegetarian discussing that problem
seen last winter. Two new phenomena
surfaced in the spring crop, namely tipburn
and internal rot. Several similarities exist
between pepper spot and tipburn,
similarities that can be corrected (or
alleviated) through simple management
practices and a better understanding of
Chinese cabbage physiology.
Tipburn appears as a grayish or
ashen discoloration generally on the leaf
margins distal to (away from) the core on
the internal leaves. Internal rot is an
actual breakdown of the tissues within the
head essentially in the same location as
that observed with tipburn. With internal
rot, tissues become translucent and water
soaked. Internal rot appears to be
associated with calcium (Ca) deficiency in
the head and is the product of overly
vigorous growth in Napa (more rounded)
Tipburn and internal rot severity is
affected by the environment (especially
warm, humid conditions), variety, and
physiological or nutritional factors. These
disorders have traditionally been
associated with Ca deficiency, abnormally
high fertilizer rates, and improper water
management (Collier and Tibbits, 1982).
Both tipburn and internal rot are
generally believed to involve a Ca
deficiency. Ca moves in the transpiration
stream, but it is not a very mobile ion; in
low or non-transpiring tissue (such as
leaves in the interior of the head) Ca may
often be deficient. Perhaps the most well
known example of Ca deficiency is blossom
end rot of tomato or watermelon.
Recent work from Japan in both
solution and field culture has shown that
ammonium (NH4-N) toxicity can be
indirectly related to tipburn in warm
season Chinese cabbage. It was proposed
that high levels of NH4-N caused root
damage which resulted in a localized water
stress, decreasing the flow of Ca to head
tissue. As Ca is preferentially absorbed at
the root tip, root damage would reduce
uptake. However, NH4-N converts rapidly
to NO3 in our warm soils (within 30 days)
so some NH4-N in the sidedress material
should not cause a problem.
Recent research in Palm Beach
county (Ken Shuler) showed 120 lbs/A is
sufficient to produce commercially
acceptable yields of Chinese cabbage
depending on the amount and frequency of
leaching rain. N applications should be
split (3) with about 50% (60 lbs/A or less)
of the N applied at early heading.
Chinese cabbage is most sensitive to
tipburn at head formation. So as with
pepper spot, heavy side dressings of
nitrogen (N) should be avoided at this
time. Interestingly, overly wet soils
(causing low oxygen) also damage roots!
Research at the SWFREC has
shown that under plastic mulch, regardless
of N source, as N rate increases tipburn
decreases. A one-time application of 120
lbs N per acre at planting caused only half
the tipburn exhibited at 60 lbs N per acre.
Decreasing tipburn incidence through
increased N application has also been
reported from Denmark for radicchio and
crisp head lettuce.
For bare ground culture, the
Japanese have found that suppression of
initial plant growth by shading (covering
with rice straw) effectively reduced both
tipburn and internal rot. However, low N
side dressings, and rigid control of soil
moisture (reduced fluctuations) played a
major role in reducing tipburn and internal
rot in their studies.
General recommendations to reduce
incidence of tipburn and internal rot
1. Use tolerant cultivars (Napa types most
2. Use appropriate rates of N and K.
3. Use split application of N and K (avoid
excessive N sidedressings at heading).
4. Irrigate uniformly.
(Vavrina, Vegetarian 93-06)
III. VEGETABLE GARDENING
A. Organic Gardening Research
and Education Park.
This educational organic gardening
site, located across Hull road from Fifield
Hall, is open for agents and master
gardeners to visit throughout the
gardening seasons. The 3rd annual field
day was held June 3rd during which the
demonstration work was summarized and
findings were highlighted. About 65
visitors attended, including agents and
several master gardeners.
For those of you who could not
attend, the following summary outlines the
type of demonstrations going on here.
Also, the first three years of the organic
soil amendment study has been presented
in the Florida State Horticultural Society
Proceedings, Vol. 105, May 1993, (just
received). The paper is on pages 263-268,
"Organic Soil Amendments for Florida
Vegetable Gardens," by James M. Stephens
and S. R. Kostewicz.
Summary of Demonstrations and Trials
1. Organic amendments: 'Whopper' tomatoes are growing in 12 gro-boxes, each
containing one of the following organic soil amendments: (a) oak leaves; (b) multiple
organic; (c) chicken litter; (d) turkey (sustane); (e) yard-waste-compost; (f) yard-waste-
compost plus organic fertilizer (Fertrell); (g) organic fertilizer (Fertrell); (h) guano; (i)
llama litter; (j) poultry compost (Red Rooster); (k) crabwaste compost; (e) dairy
2. Organic garden: Demonstrates the proper way to grow a general vegetable garden
organically (includes a mini-garden).
3. Mounds: An observational trial showing 'Whopper' tomatoes grown on compost
mounds with various kinds and rates of organic fertilizer incorporated.
4&5. Green manure (replicated trial): Plot not previously fertilized, compared with plot
previously fertilized with animal manure. Both planted with Austrian winter peas
and crimson clover.
6. Edible landscape: Area along fence and around garden shed planted with vegetables
and flowers for aesthetic effect.
7. Tomato trellis: Several techniques for staking and trellising tomato plants are
8. Mixed planting: Area includes novelty potatoes (blue, gold, topato), strawberries, and
9. Jicama and Southern pea variety demonstration.
10. Mulching study (replicated) using fall cabbage ('93) and spring ('93) okra as test crops.
11. Cover Crop: Hairy vetch, seeded last year, has been allowed to re-seed.
12. Tropicals intercropping: Demonstration of selected tropical fruits such as papaya and
guava, intercropped in North Florida.
13. Fallow: Plot kept fallow for future studies.
14. Sweet potato: Germ plasm study. Various plasmic combinations are under
observation for possible genetic contributions.
15. Seminole pumpkin: This pumpkin from Florida's past is under evaluation for
selections with potential as jack-o-lanterns.
16. Living mulch: A cover crop planted in the winter is inter-cropped with sweet corn to
evaluate the effects as a living mulch (replicated).
17. Student gardens: The course on organic gardening is taught here in the fall semester;
this spring (93) a millet cover crop rate of seeding trial is planted (replicated).
18. Vegetable specimens garden: Designated site for the planting and observation of
uncommon vegetable kinds and varieties (partially utilized Spring '93).
19. Composted yard-waste trial: Pole beans planted to determine effects of various rates
and combinations of composted yard waste (replicated trial in it's 3rd year).
20. Mulched chestnuts: Chestnuts grown organically on a contour are test crop for winter
cover crop cut and evaluated as a mulch (replicated).
21. Small fruits demonstration: The organic culture of several door yard fruits including;
figs, jujube, black mulberry, blackberry, and grapes, is demonstrated.
22. Allelopathy study: A tomato relative L. hirsutum is under evaluation for its
allelopathic effects on weed species as an alternative to herbicides.
23. Insect management studies: Biorational insect control methods are under
investigation by the Entomology Department. (Replicated).
24. Herb garden: This herb garden, established Spring 1993, is a cooperative organic
display garden with members of the Alachua County Master Gardeners.
(Stephens, Vegetarian 93-06)
Prepared by Extension Vegetable Crops Specialists
Dr. D.J. Cantliffe
Dr. S.M. Olson
Mr. J. M. Stephens
Dr. G.J. Hochmuth
Dr. S.A. Sarg nt
Dr. C. S. Vavrina
Dr. D.N. Maynard
Dr. W.M. Stall
Dr. J. M. White