[tomato] Mycorrhizal Fungi Experiments

Doreen Howard (Tomato@GlobalGarden.com)
Wed, 18 Feb 1998 20:29:12 -0600 (CST)

Louis wanted mycorrhizal fungi talk!!  Here's what I did with VAM
strain mycorrhizae in 1997.
Experiments with Mycorrhizal Fungi and Tomatoes
(Heirloom and Hybrids)

Doreen Howard

Premise:  Tomato plants inoculated with mycorrhizal (VAM) fungi will
outproduce control tomato plants that are not inoculated.

Conditions:  This experiment took place in Angleton, Texas, which is 42
miles south of Houston, near the Gulf of Mexico.  The USDA climate zone is
9, but the microclimate which is moderated by sea breezes is actually zone
9B.  The first frost date is about Dec. 10 and the last frost date is March
5.  However, freezes occur usually in only one out of
three years.  Temperate weather in which tomatoes can set fruit is between
March 5 and approximately April 25.  After that date, nightly temperatures
climb above 75 degrees. Annual rainfall is about 65 inches.  Humidity
averages 75-95% year-round.  Naturally occuring soil is gumbo clay.

Subjects:  The following tomato varieties were used in this experiment:  
	Hybrids:  Carnival, Odoriko.
	Heirlooms:  Wonder Lite, Green Zebra, Black Plum, Silvery Fir         Tree,
	German, Purple Smudge, Schimmerg Stoo, Garden Peach, Gurnsey
Island, White Bush, Southern Night.

Method:  All tomato plants were grown from seed in flats.  Half were
inoculated with the fungi when potted up to 2-inch containers, approximately
two weeks after sowing. The other half were not.  Of the inoculated half, 50
percent were fertilized with pelleted fish
meal and trace element volcanic minerals and 50 percent were fertilized with
Osmocote (14-14-14 with trace elements).  A pinch of inoculant, 1 teaspoon
pelleted fish meal (9-3-5) with a pinch of trace element volcanic minerals
or a pinch of inoculant and 1 teaspoon of Osmocote were placed under each
transplant.  The control plants were potted with l
teaspoon of pelleted fish meal and a pinch of trace element volcanic minerals.

Transplants were allowed to grow under horticulture lights and outdoors in a
sheltered area for four weeks.  Most were potted up into larger containers
twice, because of rapid growth.  The inoculated transplants (both the fish
meal and Osmocote fertilized ones) were markedly sturdier and bushier than
the control plants.  At the end of this six week
period some of the inoculated plants had flowers on them.

On March 5, 1997, all plants were set out in beds that were 5 feet apart and
separated by clay soil overlaid with St. Augustine turf.  The control plants
were set in one bed that was 4 feet by 28 feet; plants were spaced three
feet apart.  A quarter cup of pelleted fish meal and a dusting of trace
element volcanic minerals were placed in planting holes. Plants were caged,
and the cages were wrapped with Reemay for weather and blight protection.
The inoculated plants were set in two beds--each one was 4 feet by 16 feet.
Osmocote-fertilized plants went into one bed, and a quarter cup of Osmocote
was added to each planting hole.  Fish meal-fertilized plants went into the
other bed, and a quarter cup of
pelleted fish meal and a dusting of ttrace element volcanic minerals were
put in each planting hole.  All inoculated plants were caged, and the cages
were wrapped with Reemay.  

The soil in all three beds was identical--composed of naturally occuring
clay soil, peat moss, compost, composted cow manure, shredded oak leaves and
alfalfa pellets added at the rate of 5 pounds per bed.  Beds were raised 8
inches above the grade and bordered with cement blocks.

The only other care given to plants (other than what is mentioned under the
observation section below) was a prophylactic weekly foliar spray of Neem
oil for early blight and other fungal diseases.  The foliar spray was
applied for six weeks. Watering was not necessary, because rainfall was more
than sufficient.

Observations:  Spring weather in South Texas was unusually cool .  Soil
temperature reflected that.  Cool nights (45 degrees) were recorded well
into April, when nightly temperatures usually reach into the 70's by month's

3/5/97		When plants were pulled out of pots to be set in the ground, white
fuzzy material was observed covering the outer edges of root balls. (Slides
3/21/97	First fruit set on inoculated Southern Night heirloom plant.
3/24/97	First fruit set on inoculated Odoriko hybrid plant.  
4/9/97	First fruit set on control Southern Night heirloom plant.
4/10/97	First fruit set on control Odoriko hybrid plant.
4/11/97	Control plants are a deeper green in color than inoculated ones.
Controls look healthier.  Inoculated Osmocote plants look better
than the fish meal ones.  The fish meal fertilized plants have
purplish leaves that seem to indicate phosporous deficiency, and
their growth has stopped.  Nights are in the low 50's.
4/14/97	Purple coloring of leaves and blossoms is more pronounced on
inoculated fish meal-fed plants.  Other inoculated Osmocote and
control plants all look fine.  Fish meal plants are each fed a
gallon of water with 1 tablespoon of 15-30-15 Miracle Gro         dissolved
in it.
4/18/97	Purple color has disappeared from affected plants and growth has
5/1/97	Picked first tomato from inoculated Southern Night plant--56 days
after setting out the transplant. This is listed as an 85-day         tomato.
5/8/97	Picked first inoculated Odoriko hybrid tomato--61 days after
transplanting. It's listed as a 76 day tomato.
5/15/97	Early blight has set in on all plants, despite the prophylatic
5/20/97	Harvest is in full swing, and early blight is pervasive.  Control
plants are complete brown and barely surviving to ripen their
fruit.  Inoculated plants are brown and  look nearly dead, except
for the top foot or so of green foliage.  However, they are
loaded with fruit, and the fruit is ripening.  It's a strange         sight.
5/24/97	Picked first control Southern Night tomato--79 days after
6/5/97	Last tomato picked and heavily diseased plants were pulled up.
Two inoculated plants that were situated next to a patch of
Truimph de Farcy filet beans have nodules on their roots.  At
first, they appeared to be nematodes, but nematodes have never
been recorded in this garden or was there evidence of nematodes
anywhere else in the garden.
6/5/97	A general observation: most every blossom on inoculated plants
set fruit, but fruit size was smaller than in previous years.
Plants were grown from seeds saved from previous crops; some
varieties have grown in this garden three years.  So the         observation
of small fruit size is based on long  term
	evaluation.  Control fruit was of average size for their various
	Over 500 pounds of fruit was harvest from 21 plants. One of the
control plants died, and control plants of every variety tested         were
not planted.

			Inoculated			Control
Wonder Lite		122 fruit			29 fruit
Green Zebra		85				26
Black Plum		314				Not Planted
Odoriko	        	82				29
Silvery Fir Tree	75				Not Planted
Striped German	         12				Plant Died
Purple Smudge	          25				7
Schimmerg Stoo	         118				28
Garden Peach		103				48
Gurnsey Island		175				71
Carnival		66				Not Planted
White Bush		36				13
Southern Night  	74				34

Mycorrhizial fungi appears to increase the fruit yield of tomato plants and
helps plants produce in adverse conditions such as heavy blight damage.
Fruit on inoculated plants matured sooner that normally expected.  Total
weight and number of fruit from inoculated plants was much higher than the
total weight and number of control fruit.  But, individual fruit from
inoculated plants were smaller than the average stated in literature and
from previous growing experience.

The nodules found on roots of several inoculated plants may have been due to
a transfer of nitrogen-fixing bacteria from surrounding legumes.  I cite
"Humic, Fulvic and Microbial Balance: ORGANIC SOIL CONDITIONING" by William
R. Jackson, PhD., p. 550, "Promotion of nodulation of symbiotic
nitrogen-fixing bacteria such as rhizobium, as reported by Mosse et al."

In cool soil where microbial activity is sluggish, plants appeared to
benefit from Osmocote to provide the nutrition they needed for initial
grown.  Organic fish meal pellets left plants showing signs of phorphorous
and nitrogen deficiencies, and Miracle Gro had to be
applied to supplement the fish meal.