|Abstract or Summary
- During the summer of 1967 a fertilizer survey was conducted
to determine the nutrient status of peppermint fields, the nutrient
concentration of plant tissue and the oil content of peppermint in
Plant and soil samples and the field's fertilizer history
were collected from cooperators in
Oregon's peppermint growing
areas in June.
Oil samples and plant samples were collected in
August and September.
Results of the survey indicated the following:
(1) Micronutrient levels of the plant tissue were relatively
high and the highest Mn concentrations were associated with lower
(2) The highest levels of total nitrogen in the leaf analyses
were associated with lower oil concentrations.
The higher N levels
appeared to be related to fields with rank stemmy growth. (3) All P levels were quite high and there were no apparent
associations between P concentration and oil concentration.
(4) There was an antagonistic relationship between K and Na
concentration within the plant and the higher oil concentrations were
associated with moderate levels of both K and Na in the plant.
(5) The majority of the oil is located within the top 15 inches
of the plant.
The results indicated major emphasis of field experiments
should be placed on time and rate of N application and the Na-K
Since P is a major fertilizer expenditure for many
growers, P should be included in the over-all nutrient evaluation.
Five experiments were established in the spring of 1968 to
evaluate the effects of N, P, K and Na fertilizers on the oil content
and nutrient concentration of peppermint in western Oregon. Nitrogen
experiments were located south of Junction City (Harper) and west
of Grants Pass (N-Fry) while P, K and Na experiments were located
west of Jefferson (Stauble), north of Corvallis (Belnap) and west of
Grants Pass (K-Fry).
The N experiments were randomized blocks with four replications.
Seven rates of N were used in combination with five application dates.
The P, K and Na experiments were randomized blocks
with three replications.
Four rates of K were applied with and
Phosphorus was applied to all but two treatments. Plant samples were collected June 25-27 at all locations and
plant and oil samples were collected at harvest.
The plant sample
consisted of the main stem from the latest matured leaves at the top
of the plant down the stem six inches.
The Stauble location was
sampled every two weeks during the growing season and both the
stems and the mature leaves on the sampled stem portion were collected.
P, K, Na, Mn, Ca and Mg were determined on the June
samples while NO₃-N and Cl were determined on the harvest sam-
ples and NO₃-N on the June samples of the N experiments.
Oil samples of about five pounds of green plant material were
taken from the center of each plot.
The sample was placed on a
wire screen and dried either in the field or the greenhouse.
After the samples had dried for two to three days, they were
placed in a cotton bag and were ready for distillation. A portable
still designed after commercial stills was used to remove the oil
from the hay.
Increasing rates of N increased the NO₃-N concentration of
peppermint stems and the oil content of the plants.
Delayed application of N did not affect the NO₃-N concentration of the plants at a
given rate of N at harvest.
However, delayed application did increase the percent oil and total oil yield.
The July 1 application
date had a significantly higher percent oil and total oil yield than
the June 1 date.
Yield of hay increased significantly to about the 250 pound rate and subsequently decreased with higher N application.
Delayed N application decreased the hay yield.
Phosphorus fertilization did not increase the P concentration
at any of the locations nor did it have any effect on the oil content.
P concentration ranged from .31 - .49 percent in the stem sample
taken June 25-27.
Potassium fertilization increased the K concentration of
peppermint with the greatest increase occurring where the soil had
a low K soil test.
However, K fertilization did not affect the oil
content. K concentration of the June stem sample varied from 2.5
to 6.1 percent..
Application of Na increased the Na concentration at all locations where Na was applied.
Sodium fertilization significantly increased the percent oil at the Stauble location and increased the
percent oil at the K- Fay location.
Hay yield was not affected by
There was a considerable amount of variation in the oil and
analysis for all experiments.
The coefficient of variation
analysis was 37.9 and 38.7 percent for N-Fry and
Harper respectively and 89 percent for Stauble.
of variation for percent oil was 14.0, 20.6, 21.7 and 14.3 percent for N-Fry, Harper, Stauble and K-Fry respectively. Since there was a large variability in the oil data, an experiment was designed to evaluate the effectiveness of the method of
handling the oil samples.
Four samples, similar in size, were
taken from peppermint variety trials that were established on uniform, first year row mint.
Drying and distillation were the same
as described for the other oil samples.
There were no significant
differences among the distillation units and the coefficient of varia-
tion was 7.1 percent..
It was concluded that reproducible results
could be obtained for oil analysis when uniform plant material was