Nursery Crop Science
Organic Fertilizers for Basil Transplant Production
Michelle McGinnis, Al Cooke, Ted Bilderback, and Mary Lorscheider
Basil is a top-selling retail herb during the spring and early summer months.
Some markets may be willing to pay a premium for basil grown under organic conditions.
Vermicompost or worm castings is often used as a sustainable soil amendment
by organic growers for transplant production, and the literature shows that
the use of worm castings can have positive effects on root development and growth,
plant development, and field crop yield.
This project was initiated to evaluate the use of worm castings as a substrate
amendment with five commercial organic fertilizers. We were interested in container
life of the organic fertilizers, effects of the fertilizers on pH, and whether
a worm castings amendment affected the behavior of the organic fertilizer.
Basil seeds (Osimum basilicum ‘Genovese’) were sown into 98-plug
trays with a peat-based substrate amended with 10% worm castings on August 15,
2002. Seedlings were grown with no fertilization, and upon the development of
the first set of true leaves were transplanted into the fertilizer treatments.
The basil seedling plugs were transplanted into ITML 4.5-inch geranium pots
(4.5-inch diameter, 3 7/8-inch high, 37 cu. in.) with 11 fertilizer treatments
and 7 replications per treatment on September 5, 2002. Treatments included 5
organic fertilizers with and without commercial worm castings (Vermicycle Organics)
and one treatment with worm castings but no additional fertilizer.
The substrate was a commercial blend of peat, perlite, vermiculite, and pine
bark to which additional perlite was added resulting in the following volumetric
analysis for the basic substrate: Peat 38.7%, Perlite 38.0%, Vermiculite 11.6%,
and Pine bark 11.6%. For the vermicompost amended substrate, worm castings were
blended into the basic substrate resulting in Peat 34.9%, Perlite 34.2%, Vermiculite
10.5%, Pine bark 10.5%, and Worm castings 10%. The following treatments were
created by mixing the indicated amount of fertilizer with either the basic substrate
or the vermicompost substrate. The fertilizers were incorporated at a rate of
1.2 g N/pot:
EHO Espoma Holly-tone 4-6-4 (30 grams)
EHW Espoma Holly-tone 4-6-4 (30 grams) with worm castings
EPO Espoma Plant-tone 5-3-3 (24 grams)
EPW Espoma Plant-tone 5-3-3 (24 grams) with worm castings
FSO Fertrell Super 3-2-3 (40 grams)
FSW Fertrell Super 3-2-3 (40 grams) with worm castings
N1O Nature Safe 8-5-5 (15 grams)
N1W Nature Safe 8-5-5 (15 grams) with worm castings
N2O Nature Safe 10-2-8 (12 grams)
N2W Nature Safe 10-2-8 (12 grams) with worm castings
WCW media with worm castings (no additional fertilizer)
The potted basil plants were set outside in the nursery in a completely randomized
block and watered in. Plants were hand watered as needed. Starting on September
10, 2002, pour-thru tests were conducted, and EC and pH measurements were obtained
for randomly selected plants for a period of 6 weeks. A composite leachate sample
for each treatment was collected at the first time point, September 10, and
submitted to the North Carolina Department of Agriculture’s Agronomic
Lab for analysis.
Endpoints measured are growth index, fresh weight, dry weight, number of fully
formed leaves, and number of lateral shoots. The growth index was calculated
by the following:
[([(max width + min width) / 2] + height) / 2 ] final - [([(max width + min
width) /2 ] + height) / 2] initial
Nutrient leachate analyses 5 days after pot up indicate the highest concentrations
of N, P, K, Ca, Mg, S, Mn, Zn, B, and Cl in one or both of the Espoma Holly-tone
treatments (EHO or EHW). The highest Cu and Na concentrations were found in
the Espoma Plant-tone with worm castings treatment (EPW).
All treatments had high levels of nitrogen, however the Espoma Holly-tone treatments
(EHO and EHW) had the highest concentration of total inorganic nitrogen, indicating
the nitrogen in this fertilizer was fast-releasing in our conditions. Ammonium
was detected in the samples from all fertilizer treatments, nitrate was detected
in the Espoma Holly-tone treatments (EHO and EHW), the worm castings only treatment
(WCW), and in the Nature Safe fertilizers with worm castings (N1W and N2W).
Urea was detected in the Nature Safe and Fertrell Super treatments (N1O, N1W,
N2O, N2W, FSO, and FSW) as well as the Espoma Plant-tone with worm castings
(EPW).
The pH readings for both Fertrell Super treatments (FSO and FSW) had the highest
pH measurements, as the only treatments with measurements above 7.5 at the first
time point (9/5/03) and the last time point (10/14/02).
A significant difference for fresh weight was found for N1W above all other
treatments. Significant differences for dry weight, growth index, and number
of fully formed leaves was found for N1W and N2W above all other treatments.
FSO, FSW, and WCW consistently rated significantly lower on the above referenced
endpoint measures. No distinct significant differences between the treatments
were noted for number of side shoots. EHW was not included in that statistical
analysis due to small sample size cause by a high mortality rate, believed to
be caused either by transplant stress or high salt content.
In conclusion:
* Nutrients from Espoma Holly-tone (EHO and EHW) released rapidly under our
conditions.
* The Fertrell Super treatments (FSO and FSW) appeared to cause undesirably
high pH under our conditions.
* Depending on desirable endpoints, economics, and/or logistics, Espoma Plant-tone
(EPO and EPW), Nature Safe 8-5-5 without castings (N1O) and Nature Safe 10-2-8
without castings (N2O) yielded saleable plants.
* The addition of worm castings to the Nature Safe treatments (N1W and N2W)
showed a significant difference with respect to growth index, number of fully
formed leaves, fresh weight, and dry weight.
