A Vegetable Crops Extension Publication
University of Florida
Institute of Food and Agricultural Sciences
Cooperative Extension Service
n Adobe Acrobat
VEGETABLE CROPS CALENDAR
Fertilizer Technology Update
IRREC Lettuce Evaluation. Fall 2000
Asian Vegetables for the Home Gardener
List of Extension Vegetable Crops Specialists
(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.)
:..", =.,. **r!
2001 FL107 In-Services:
Feb. 13: Strawberry in-service training. GCREC-Dover. Contact: John Duval.
March 5-8: Florida Postharvest Industry Tour. Contact: Steve Sargent.
April 23-25: Beneficials and Biorationals for Vegetable Pest Management. Contact: Susan Webb.
r ij loll
Fertilizer Technology Update
I recently wrote a report on fertilizer technology for Miami-Dade County Agricultural and Rural
Land Retention Study. I like to present it to our Newsletter readers and hope you will find it
Fertilizer technology is changing unceasingly every decade. These changes include new fertilizers
and new application methods. I divided fertilizer technology into 7 groups: 1) dry granular
fertilizers, 2) fertigation, 3) foliar fertilizers, 4) controlled/slow release fertilizers, 5) soil organic
amendments, 6) mycorrhizae, and 7) magical/mysterious products. In the following section, each o
these groups will be discussed in terms of their development and potential impact on crop
production in south Florida.
Dry granular fertilizers:
Dry granular fertilizer is still and will continue to be a major fertilizer source for crop production in
Miami-Dade County. It is relatively inexpensive and always available from fertilizer distributors.
Most large-scale growers have their own machinery for fertilizer application, while small-scale
growers always get help from fertilizer distributors. Most growers have relatively more knowledge
of this group of fertilizers than of any others. The changes of dry granular fertilizer technology will
be 1) specific fertilizer for specific crops and 2) application technology. Special fertilizer such as
"palm special", "lawn special", "tomato special", "lychee special", etc. will become progressively
more available to growers. These special fertilizers are manufactured or mixed with distinct
nutritional formulas to meet specific needs of the crop. However, variation between fields and
between varieties should be considered also when selecting a special fertilizer. Another set of
adjustments in the use of dry granular fertilizer involves application timing and rates. A recent
fertilizer management survey for tropical fruit crops in south Florida showed that growers apply
fertilizers 1-12 times per year for total amounts of 5 445 Ib N/ac. These large variations indicate
that it is necessary to optimize fertilizer application frequencies and rates.
Fertigation is the application of liquid fertilizer through an irrigation system. The technology was
developed in the 1970s and its adoption continues unabated to the present. Almost all tomato
growers in Miami-Dade County use fertigation. Fertigation also has been used for other vegetable
crops such as squash, eggplant, cucumber, etc. Our survey revealed that about 53% of tropical
fruit growers are using either fertigation or soil drenches in their groves. Various innovations in
fertigation equipment are being developed and marketed to growers. Research information is also
more available though traditional publications and internet access. The advancement and
progressive adoption of fertigation technology is certain to improve fertilizer use efficiency,
overcome micronutrient deficiencies and reduce leaching of nutrients into groundwater.
Foliar fertilizer technology came into use early in this century, but did not become common practice
until the 1980s. This slow adoption was caused by the scarcity of fertilizer sources and appropriate
application equipment. The application of foliar fertilizers is the quickest way to deliver nutrients to
the tissues and organs of the crop. However, the plant leaf is structured in such a way that it
naturally resists ready and reliable penetration of fertilizer salts. This is particularly true of N, P,
and K. Research in Florida clearly shows that foliar application of N, P, and K does not result in
consistent yield increases. Indeed some recent work has documented severe yield reductions with
foliar nutrient sprays. On the other hand foliar application of micronutrients can be beneficial to
correct certain nutrient deficiencies. However, a micronutrient formulation should be applied only
when a specific deficiency has been clearly diagnosed. Based on over 30 years of experience with
vegetable production in south Miami Dade County, Dr. Herbert H. Bryan concluded that only Fe
and Mg foliar fertilizers effectively overcome corresponding micronutrient deficiencies of
vegetable crops in this area.
Slow/controlled release fertilizers:
Slow release fertilizers are often interchangeably designated "delayed release", "controlled
release" or "metered release" formulations. Such a formulation has a rate of dissolution (usually in
water) much less than the rates for completely water-soluble compounds. Controlled/slow release
fertilizer technology was developed in the 1960s, but became commercially available only in late
1970s and early 1980s. A recent fertilizer survey in Miami-Dade County showed that 18% tropical
fruit growers use slow or controlled release fertilizer formulations. Price and availability of such
formulations still restrict their use in traditional crop production. The quality of fertilizer is also of
major concern. However, the development of new technologies for controlling nutrient release will
lead to improvement in prices and quality of slow release fertilizer formulations.
Soil organic amendments:
Soil organic amendments usually consist of animal manures, cover crops, or composts. In many
instances animal manures are the best source of organic matter. Indeed since the beginning of
agriculture, animal manures have been used effectively for crop production. Animal manures
supply significant quantities of essential plant nutrients and increase soil organic matter. However,
availability, transportation costs, and regulations limit widespread use of animal wastes in crop
production in Miami-Dade County. Cover crops, commonly referred as green manure, are also
important soil organic amendments for sandy or gravelly soils in this area. Cover crops are used to
improve soil physical properties, increase soil organic carbon, conserve soil water, reduce surface
runoff, and recycle nutrients during the heavy summer rains. Sunn hemp (rotalariajuncea L.),
one of the new cover crops in south Florida, was found to produce 8.5 to 11.3 metric ton dry weigh
ha-1 and to fix or retain up to 270 kg N ha1. A series of cover crop projects are currently in
progress in Miami-Dade County. Composts have been increasing in popularity as soil organic
amendments. Research has demonstrated that compost can serve as a soil amendment to
increase organic matter, improve microbial activities in soils, provide nutrients, and ultimately
improve plant growth and yield. However, composts are produced from various organic wastes anc
consequently, environmental concerns are always an issue in compost utilization. The potential
often exists for heavy metals to accumulate in the soil and sometimes in the edible plant parts of
vegetables and fruits. Yet, this is not as likely to occur in the County's calcareous soils as may
occur in the acidic sandy soils further north. Nevertheless excessive nutrients or metals released
from composts may be leached out of the root zone and into groundwater by irrigation or by
rainfall. Other hazards such as human pathogens, viable weed seeds, and plant phytotoxicity
should be considered when developing vegetable production systems with compost.
Mycorrhizae are certain soil fungi which for symbiotic associations with plant roots. These
beneficial symbioses are ubiquitous in nature and almost all vascular plant species have some
form of mycorrhizal association. Mycorrhizae were discovered in 1840, but were not studied
extensively until the 1990s. Most research focused on the potential of mycorrhizal fungi to improve
crop yields and to reduce the use of fertilizers. A recent experiment conducted in the Tropical
Research and Education Center, University of Florida indicated that lychee plantlets derived from
air-layers and inoculated with mycorrhizal fungi grow and develop much more rapidly than those
which are not exposed to these beneficial symbionts. Many other scientists have reported
significant functions of mycorrhizal fungi in crop production. However, such promising research
results have not led to significant commercial utilization of mycorrhizae. Nevertheless, mycorrhizae
are likely to play a very important role for crop nutrient management in the future.
There are many magical/mysterious products, derisively known as "snake oils", marketed by
various companies or individuals. These products are often referred to as biostimulants, soil
supplements, soil conditioners, natural fertilizers, soil additives or growth activators. So far, few of
them have demonstrated significant impact on crop production. Some of them have either no
effects or negative effects on crop growth. Others are said to reveal their beneficial effects only
under certain conditions of plant stress. However, I hope someday some products from this group
will make significant contributions to crop nutrient management.
(Li, Vegetarian 01-01)
IRREC Lettuce Evaluation, Fall 2000
A replicated lettuce variety trial was conducted in the fall of 2000 in conjunction with the
Commercial Production of Cool Season Vegetables class (Fig. 1). A wide variety of specialty
lettuce cultivars are on the market for home and small-scale commercial production and are
becoming popular in local restaurants and farmers' markets. The cultivars selected included a
variety of leaf types (oakleaf, lollo, butterhead, iceberg, romaine) and leaf colors.
Fig. 1. Students evaluating lettuce variety trial at Indian River Res. and Edu. Ctr.
Seeds were sown 8/30 in Fafard germination mix and germinated in a shade house. The trial was
conducted in an Ankona fine sand. Beds were 44 inches wide and 8 inches high on 7 foot centers.
Total fertilizer applied was approximately 160:160:160 N:P205:K20/A with 25% broadcast and the
remainder banded in the bed. Beds were covered with white on black plastic polyethylene mulch.
Seepage irrigation was used.
Transplant date varied with development of the plants (Fable 1). Plants were spaced 10 in. apart
within rows, with 2 rows per bed and 12 in. between rows. Four replicates of each cultivar were
planted with 10 plants per plot in each replicate (5 per row). Plants were scouted throughout the
season and there was very little insect or disease pressure. Registered pesticides were applied as
needed to control pests.
The 6 inner plants within each plot were harvested and average diameter and average head weigh
calculated (Table 1). Harvest dates were determined by observation.
Cultivar Type Color Source Dayspt Days to diameter head
transplant harvestz (in) weightY
Terlana Romaine Green
Leander Romaine Red
E16.2716 Romaine Green
E16.3228 Romaine Green
Enza Zaden 29 41 15.3 2.0
Enza Zaden 29 28 10.7 0.5
Enza Zaden 42 40 12.0 1.4
Enza Zaden 42 28 12.7 1.0
Green Forest Romaine Green
Glossy Leaf Green
Tiara Leaf Green
Redina Leaf Red
Noisette Leaf Green
E15.2702 Leaf Red
E15.0622 Leaf Green
E15.5793 Leaf Green
Valencia Oakleaf Red
Royal Oak Oakleaf Green
Burpee Bibb Butterhead Green
Optima Butterhead Green
Lollo Rosa Lollo Red
Crispino Iceberg Green
ZDays from transplanting to harvest
Xlnformation not available
I I II
Days to harvest were within expected values (Vegetable Production Guide for Florida SP170) for
all cultivars (70-95 days for iceberg, 60-80 days for all others). The transplant production period
was longer than expected, especially for Redina (Fig. 2), Crispino and Lollo Rosa. Earlier than
recommended planting dates and higher than optimum temperatures at planting may have slowed
the initial growth of the transplants. Red colors are reported to fade under high temperature
conditions but did not in this trial, particularly in the dark red Redina. Quality was high in all the
cultivars although Terlana (Fg. 3) and Green Forest bolted quickly after reaching marketable size.
Recommended cultivars from the quality evaluation by the class included Green Forest, Optima
(Fig. 4), Royal Oak (Fig. 5), Valencia, Noisette and Redina.
Fig. 2. Redina
Fig. 3. Terlana
r. ;'.'W ..' ..
Fig. 4. Optima
Fig. 5. Royal Oak
(Lamb, Vegetarian 01-01)
J;. .,^'^-,^ -.. I.-^ .,^^. if. .. \,? :-^ ; -
S *i ;. : .,
"m ,, .. .- .
;, t ..i- .. ...^ .:.. .... '* : ._ .^.j 1 .-
.' ". .. .. -..= --. -
.. ^ .. ^ -^ -r..- i. ; ..
Asian Vegetables for the Home Gardener
The following vegetables are popular in gardens in Taiwan. Many are suitable for Florida gardens.
The source is the Department of Horticulture, National Taiwan University (1988).
Chai Er Tsai
Chinese matrimony vine
Golden banded lily
Scarlet runner bean
Vegetable soy bean
Chinese water chestnut
Common white basella
East Indian lotus
Mung bean sprout
Net bearing dictyophara
New Zealand spinach
Old world arrowhead
Oriental pickling melon
White flowered gourd
White jelly fungus
(Stephens, Vegetarian 01-01)
Extension Vegetable Crops Specialists
Daniel J. Cantliffe Mark A. Ritenour
Professor and Chairman, Horticultural Sciences Department Assistant Professor, postharvest
Timothy E. Crocker
Professor, deciduous fruits and nuts, strawberry
Assistant Professor, strawberry
Assistant Professor, vegetable production
Elizabeth M. Lamb
Assistant Professor, production
Assistant Professor, soils
Donald N. Maynard
Stephen M. Olson
Professor, small farms
FastCounter by LinkExchange
This page is maintained by Susie Futch....
Ronald W. Rice
Assistant Professor, nutrition
Steven A. Sargent
Assistant Professor and Editor, vegetable nutrition
William M. Stall
Professor, weed control
James M. Stephens
Professor, vegetable gardening
Charles S. Vavrina
Associate Professor, transplants
James M. White
Associate Professor, organic farming
if you have any questions or comments, contact me at