The effects of plant growth-promoting rhizobacteria (PGPR) and different
potash fertilizers on diseases, growth, and yield of no-till and conventional
tillage staked tomatoes were evaluated in a factorial experiment. Eight
different tillage-PGPR-potash combinations were included in the study. In this
fifth year of the continuous no-till system, no-till tomato production led to
slower plant growth and lower yields than the conventional tillage system. Use
of sulfate of potash instead of muriate of potash increased plant growth early
in the season, but led to an increase in the incidence of Sclerotinia stem rot.
Yields of extra-large tomatoes were increased with sulfate of potash while
yields of medium and large tomatoes were decreased. Use of PGPR increased the
growth of transplanted tomatoes. Early yields were also increased with PGPR
without affecting total yields.
Introduction
West Tennessee silt loam soils are some of the most highly erosive soils in
the United States. No-till production of West Tennessee row crops has increased
significantly in recent years as growers have learned the advantages of this
production system and as UT researchers have developed the management techniques
needed for successful no-till production of cotton, corn, and soybeans.
Advantages include decreased soil erosion, improved soil structure, increased
water infiltration, and more timely access to fields for applying pest
management sprays or for conducting planting and harvesting operations. Some of
these advantages, e.g. improved soil structure and water infiltration, are not
fully realized until no-till production systems have been continuously used for
several years.
Most research on no-till production of vegetable crops has not been of a
continuous nature. Fields are tilled in the fall to plant a winter cover crop,
such as wheat or hairy vetch. The cover crop is killed the following spring with
herbicides, then vegetable crops are planted using no-till production
techniques. At the end of the growing season, however, the field is again tilled
and seeded with another winter cover crop. The research reported here seeks to
evaluate the effects of a continuous no-till production system on diseases,
growth, and yield of staked tomato. Effects of other management decisions, such
as fertilizer choice, are incorporated into the study. Their specific location
within the test changes each year.
Materials and Methods
Site description. The soil in the test field was a Calloway-Henry silt
loam complex, 0-2% slope with 1% O.M., high soil test levels of available P, and
moderate to high soil test levels of available K. The soil contained over 1280
lb Ca/acre, over 64 lb Mg/acre, and approximately 5 lb Zn/acre. Soil pH in plots
ranged from 6.0 to 7.0 with a mean pH of 6.6 (fall 2000 soil tests). Pelletized
Dolomitic Limestone with a Tennessee Relative Neutralizing Value (RNV) of 98.2
was hand-broadcast Feb 4, 2001, as needed over each 5 x 50 ft. plot at rates
recommended by the fall 2000 soil tests.
Experimental design. The 2001 test was a factorial experiment with three
factors: (1) tillage (i.e., no-till vs conventional tillage), (2) use of Plant
Growth-Promoting Rhizobacteria (hereafter referred to as PGPR) (i.e., use of
BioYield vs none), and (3) potash source (i.e., muriate vs sulfate). Each of the
eight possible combinations of these factors was replicated four times in a
randomized complete block design.
Tillage. The no-till plots had not been tilled since the fall of 1996
when they were seeded with Kentucky 31 tall fescue, while conventional tillage
plots were tilled annually. In the 2001 test, a
'middle-buster' was used to simulate the use of a chisel plow in the latter
plots. On April 9, the middle-buster with a single center shank was pulled down
the middle of each conventional tillage plot, cutting a furrow 7 in. deep and 45
ft. long. The center shank was then removed and the remaining two shanks mounted
on the toolbar 32 in. apart (16 in. on either side of the former center shank).
The middle-buster was then pulled through the plots a second time with this new
configuration, creating a ridge down the center of the plot and cutting two new
furrows 5-6 inches deep on either side of the ridge. Hand rakes were used to
pull soil tossed outside the conventional tillage plots by the second pass with
the ‘middle-buster’ back into the plots (i.e., off the undisturbed grass
beside the plots). A small disk was run over the plots (twice) on April 10 to
cut-up large soil clods and to reduce the height of the ridge. After all
operations were complete, the plots appeared as a tilled strip, 6 ˝ ft. wide,
with a low ridge, 2 - 3 in. high, down the center of the each plot.
Fertilizers. The first application of nitrogen to both no-till and
conventional tillage plots was on Apr 11, 3 ˝ weeks before setting transplants,
at 15 lb N/4356 row-ft as a broadcast strip down the center of each plot.
Nitrogen was applied after setting transplants six additional times (May 8 and
18; June 5, 13, 21, and 27) to all plots as sidedressings at 15 lb N/4356 row-ft
per application. All plots were fertilized twice with potash at 30 lb K2O/4356
row-ft per application, once 3 ˝ weeks before setting transplants and again as
a sidedressing one month after transplanting.
Transplants. Greenhouse-grown ‘Mountain Fresh F1' tomato transplants
were used for all treatments in 2001. Tomatoes not receiving PGPR were
seeded in 72-cell Speedling trays filled with Pro-Mix BX on March 14. Tomatoes
that received treatment with PGPR were seeded in 72-cell Speedling trays on
March 26. The latter trays were filled with Pro-Mix BX to which PGPR had been
added. PGPR were incorporated into the potting mix by mixing one liter of
BioYield with 39 liters of dry Pro-Mix BX to achieve a ratio of 1 part BioYield
to 40 parts treated mix. [BioYield contains two difference species of bacteria
that are purported to promote plant growth and yield.]
Other Cultural practices. Herbicides, supplemented with occasional mowing
or hand-hoeing, were used for weed control. Roundup-Ultra at 1.5 quart/acre
(2.0% solution) was applied down the center of no-till plots on March 15 in a
30-inch-wide band. Roundup-Ultra (2.0% solution) was applied to both no-till
plots (30-inch-wide band) and conventional tillage plots (84-inch-wide) on April
5. A final application of Roundup-Ultra (2.0% solution) on May 3 was applied to
both conventional and no-till plots one day before setting transplants to kill
emerging yellow nutsedge.
The test was planted on the morning of May 4 using a modified mechanical
transplanter (18 transplants/row). Plants were suckered once. Plots were
irrigated as needed to avoid moisture stress and to help dissolve sidedressed
fertilizers using a drip irrigation system consisting of 0.5 gallon/hr emitters
spaced every two feet along side tomato rows. Plants were tied to stakes using a
modified ‘Florida weave’.
Poast at 1.5 pint/acre was applied as a directed spray on each side of rows
on June 8 to both no-till plots (18-inch-wide bands) and conventional tillage
plots (18-inch-wide bands). Sencor 75 DF at 1.25 lb/acre was applied as a
directed spray on each side of the rows on June 12 (15-inch-wide bands, no-till
rows; 42-inch-wide bands, conventional tillage rows).
Fungicides were applied four times using a hydraulic sprayer: three
applications of Quadris 2.08 SC at 5.8 - 6.2 fl oz/acre/application (on May 25,
June 18, and July 24) plus one application of Bravo WeatherStik at 1.3
quart/acre (on June 29). Insecticides were applied five times: SpinTor 2SC at
5.8 fl oz/A on May 25 and Asana XL at 7.0 - 9.6 fl oz/acre on June 18, June 29,
July 24, and July 30. All fungicide and insecticide sprays were applied at 300
psi using a hydraulic sprayer equipped with one to four (depending on plant
height) ceramic, hollow-cone drop nozzles on each side of rows.
Data collection. The heights of all plants were recorded May 19 and June
22. Plots were checked every 1-2 weeks for the presence of any diseases, and
disease incidence or severity ratings were collected as appropriate. Tomatoes
were picked 2-3 times/week from July 6 through August 7 at the 'breaker-stage'
of maturity (10 harvests). A final (11th) harvest of all green tomatoes of
marketable size remaining on plants was made on August 7-8. Harvested tomatoes
of marketable quality were graded by size into four categories: small (7 x 7
boxes), medium (6 x 7 boxes), large (5 x 6 boxes), and extra-large (4 x 5
boxes). Yields (boxes/acre) in the following tables are based on 3600
plants/acre. Small tomatoes were considered unmarketable and are not included in
yield tables. All disease, growth, and yield data were subjected to analysis of
variance (ANOVA) for a factorial experiment with a randomized complete block (RCB)
design.
Results and Discussion
There was no difference in the mean heights of tomato transplants grown with
or without BioYield; transplants with either treatment averaged 5.3 in. tall
when set. Mean plant height by June 6 was significantly greater with use of
BioYield than without BioYield (Table 1). Use of sulfate of potash instead of
muriate of potash also increased mean plant height (Table 1). In contrast, mean
plant height was significantly decreased with no-till compared to conventional
tillage (Table 1). The growth advantage with BioYield was still apparent two
weeks later but not the benefits with sulfate of potash.
The 2001 test was the second time in the five-year study in which significant
disease losses were noted early in the growing season. Three tomato diseases
were observed on the West Tennessee Experiment Station during the spring and
early summer. An outbreak of Sclerotinia stem rot (white mold) appeared in early
May and eventually killed many plants. Disease losses were significantly greater
in plots receiving sulfate of potash than with muriate of potash (Table 2).
Southern blight and tomato spotted wilt virus appeared in late May and killed or
stunted an occasional plant throughout the remainder of the season. No treatment
factors significantly affected the incidence of the latter two diseases (Table
2).
Total marketable yields were significantly higher with conventional tillage
than with no-till (Table 3). This was largely due to a significant increase in
the number of extra-large tomatoes. Sulfate of potash also significantly
increased the number of extra-large tomatoes, with concomitant decreases in the
number of medium and large tomatoes (Table 3). Total marketable yields were not
significantly affected by potash treatment despite the significant differences
in plant loss to Sclerotinia stem rot with sulfate of potash.
Use of PGPR (BioYield) significantly increased early yields (first six
harvests) of marketable tomatoes (Table 4). The highest yield during this period
was with conventional tillage combined with use of muriate of potash and
BioYield (Table 5). Highest marketable yield for all 11 harvests was with this
same combination, though it did not differ significantly from other seven
combination treatments (Table 5). Severe yield losses due to insect damage were
incurred during the middle of July as corn ear worms moved from a nearby sweet
corn test to the tomatoes. When the total weight of fruit produced per plot
(including culls and small tomatoes) was examined, yields with use of BioYield
were consistently higher than those without BioYield for the first ten harvests,
although not always at the 0.05 probability level (Table 6). The potential for
BioYield to increase yields of marketable tomatoes, particularly early yields,
needs to be verified with additional tests. The trends in the 2001 test at
Jackson appear promising.