Chapter 4: Ginseng nutrition
As with all perennial horticultural crops, it is important to review the nutrition requirements of ginseng in order to ensure a thrifty, healthy plant is produced.
First off, it should be noted that ginseng does not require a heavy annual dose of fertilizer. If a ginseng garden is situated on a silt loam soil, there will often be enough natural fertility to ensure good growth. Cultivation of ginseng is often compared to raising a vegetable garden. If the proposed planting site has grown a successful garden it will also grow some very productive ginseng.
Soil fertility
In its native environment wild ginseng is found on rich loose
soils. Essential nutrients are derived from the natural decomposition
of leaves and twigs that shade the ginseng plants. The soil colloids
release essential elements to the foraging ginseng roots in small,
metered amounts. Moderate foliage growth is in line with slow
but steady root development.
When ginseng is grown on land that has been cropped or has been in a grass pasture, the soil environment is quite different from that in the native deciduous forest where ginseng grows wild. The soil organic matter may have been reduced through tillage. Liming may have altered the soil pH. In order to understand why supplemental fertilizer applications on cultivated ginseng are needed, we first must review the major and minor elements required for ginseng growth.
Essential
elements
The major soil elements required for ginseng growth include nitrogen
(N), phosphorous (P), and potassium (K). These are the elements
that will have the greatest effect on plant growth. These are
also the elements that make up the bulk of fertilizer material.
Each element needs to be understood as to how it will effect plant
growth and development.
Nitrogen
Nitrogen is responsible for all phases of plant growth and development
including photosynthethis. Plants that have adequate N show a
deep green leaf color, and full size leaves and stems. Without
adequate N leaves will be yellow and stunted.
Nitrogen always receives the most attention in soil nutrition. In the case of ginseng too much nitrogen can be detrimental to yield as excessive leaf growth can contribute to plant crowding. A deep rich silt loam soil will release N in the process known as mineralization. Soil bacteria break down the organic nitrogen into the ammonium ion. Another group of bacteria in turn converts the ammonium into the nitrate ion, in a process known as nitrification. Nitrates can be absorbed by plants, utilized by soil bacteria, or lost due to leaching on light textured soils. Soil testing usually does not include N due to the wide variation of forms of which it is found in the soil. Growers often add nitrogen either in a blend with phosphorus and potassium, or as a mixture with sulfate, such as ammonium sulfate. This latter form of nitrogen is the least expensive. The only problem with using ammonium sulfate continuously over time is that it will lower soil pH.
Organic N
Organic gardeners cherish the use of composts derived from animal
manures, as well as plant decomposition, to supply nitrogen. It's
best to add any manure prior to planting and then till it into
the soil. In British Columbia, there are reports of growers using
more than 40 tons per acre of cow manure in the spring of the
preparation year. Be sure to only use well-rotted manure, as the
relatively high N value may harm ginseng seeds. Compost, of all
forms, is a rich type of organic nitrogen, which slowly breaks
down over time, as opposed to the more immediate release of N
from synthetic fertilizers. Wild ginseng, growing in the forest,
is naturally using the organic N supplied from leaf litter decomposition.
Manure has no place in the mature ginseng garden during the final year of root growth. The roots can absorb the off-flavors from the manure!
Phosphorus is applied as a phosphorus salt in a blended fertilizer or as rock phosphate. Once in the soil, P tends to form insoluble compounds thus greatly minimizing its mobility. It is important to test for P before planting ginseng as it is generally broadcast and incorporated. P is important in all phases of ginseng plant growth. A pre-plant soil test should reveal 40-50 ppm of P as measured by the Bray method. Since this element is considered immobile in the soil, it is best to apply the amount needed and then incorporate it into the plow zone prior to planting the beds. Growers can apply both phosphorous and potassium as a blended mixture such as a 0-20-20 prior to planting. In latter years, a complete fertilizer, such as a 20-20-20 is often recommended on ginseng.
Table 1. Phosphorus recommendations for ginseng west of the Cascades
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Table 2. Potassium recommendations for ginseng west of the Cascades
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Calcium
Calcium is important in building plant cell walls, and in energy
transfer. As a major component of lime (calcium carbonate, 40%
calcium), the positively charged calcium ion is attached to the
soil colloids. Under conditions of excessive rainfall, as is the
case west of the Cascades, the calcium ion can be washed off the
colloids and replaced by the hydrogen ion which thus increases
the soil acidity. Chapter 4: Site Preparation reviewed the amount
and application method for supplying calcium. Recall the optimum
soil pH listed was 5.6-5.8.
Low pH damages
ginseng
Low soil pH is a real threat to ginseng production. Acidic soils,
high in native organic matter, tend to form aluminum complexes.
In a survey of ginseng gardens, leaf tissue aluminum levels higher
than 150 ppm was found to reduce dry weight yield by 2/3rd's.
Adding compost to low pH soils helps considerably, as the aluminum
ion will cling to the compost thus taking it out of the soil reaction.
It's best to add the compost, or grow a green manure crop and
till it under, prior to planting ginseng so that the organic matter
gets mixed into the future ginseng root zone.
High soil
pH
In areas east of the Cascades, growers should test for high pH
soils. On clay sites, a soil pH of 6.0 produced 20% root rot in
ginseng. At pH 6.5, 30 % root rot was found. Chapter 4: Site preparation
reviewed the use of elemental sulfur to lower high soil pH.
Minor soil elements
Of the minor elements most important for ginseng growth, boron
is usually considered first. Western soils often are deficient
in this soil mobile element. Growers should soil test for this
element in the fall prior to bed shaping. The product known as
Solubor (20% boron) can be worked into the soil, or sprayed onto
the foliage of the plants during the summer. The typical boron
application rate is 5 pounds of Solubor applied as a foliar spray
to first year beds as the plants are first emerging. It is very
important to calibrate boom sprayers prior to applying boron.
Over applications (2-3 times as much) can be toxic to the plants.
Solubor can be tank mixed with spring fungicides to cut down on
the number of trips through the garden.
Soil sampling
Soil samples are collected from the proposed garden site during
spring of the preparation year. A composite sample, collected
form the plow zone (beneath the native turf in the pasture), should
consist of 25-30 cores (or shovel fulls). Place the cores into
a clean plastic pail. One mixed sample of soil should be adequate
for a one acre garden. If there are obvious differences in soil
texture, or native vegetation, it's best to collect and submit
separate samples. Submit samples to an analysis lab that can make
recommendations for ginseng. Be sure to ask first, as many labs
don't have data or recommendations for ginseng.
Foliar testing
Soil sampling is advised before planting perennial horticultural
crops. Once they are established however, foliar tissue testing
will provide a better understanding of plant nutrition. For diagnosing
suspected nutrition problems, soil sampling simply can not provide
the degree of accuracy of foliar sampling. Foliar samples should
consist of 20-30 ginseng leaves randomly collected from throughout
the garden. If foliar nutrient deficiency is suspected, one sample
should be collected from the abnormal area, while another one
would be collected from the healthy portion of the garden. Ginseng
growers often use foliar fertilizers on their garden in the spring
and then submit leaf tissue samples in July. There is no point
in sampling in the spring as the new leaves are first starting
to grow. Leaf nutrient composition is highest in the spring and
then declines to a stable level in July. All of the data on ginseng
leaf nutrient composition is standardized for the July time period.
Table 3 provides a summary of the suggested sufficient levels of major and minor elements. This data comes from Dr. A Khawaja, at K Ag Laboratories International, Inc. in Oshkosh, Wisconsin 54901.
Table 3. Foliar standards for North American ginseng
| Nutrient | Units |
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| nitrogen (N) | % |
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| phosphorus (P) | % |
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| potassium (K) | % |
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| calcium (Ca) | % |
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| magnesium (Mg) | % |
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| sulfur (S) | % |
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| zinc (Zn) | ppm |
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| boron (B) | ppm |
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| manganese (Mn) | ppm |
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| iron (Fe) | ppm |
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| copper (Cu) | ppm |
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| aluminum (Al) | ppm |
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| molybdenum (Mo) | ppm |
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Summer leaf
symptoms
The natural growth habit of ginseng is to begin transferring nutrients
from its leaves to it's roots in late summer. Figure 1 shows the
leaf margins beginning to yellow as the plant is entering dormancy
in late summer. This natural phenomenon should not be confused
with nutrition standards for ginseng.
Woods cultivation
and fertility
In its natural wooded environment ginseng has to compete with
tree roots and soil bacteria that are all competing for the available
nutrients. Woods cultivated ginseng should receive very little
if any synthetic fertilizer as supplemental applications will
tend to rapidly accelerate the growth of the roots. Buyers of
either woods cultivated or wild simulated root have come to expect
a number of closely spaced rings on such roots indicating relatively
slow annual growth.
Typical fertilizer
practices
Growers have found that the best time to fertilize their established
gardens (years 2 through 4) is in late winter (March). This practice
will supply the plants with nutrients as they need it to resume
growth. Fall fertilization has not proven to be nearly as efficient
as the winter rainfall tends to wash the nutrients through the
soil profile. Typical application rates include 120
lbs/acre of a blended 20-20-20 synthetic
fertilizer.
If an established garden looks anemic in late May, June, and July,
foliar nutrients can be applied. Use a rate of application of
2 lbs of a 20-20-20 fertilizer, in 100 gallons of water. Use a
boom sprayer to cover the entire canopy.
Fertilization
in year 1
For first year plants there is a danger of burning the young growth
with granular fertilizer. A better solution would be to wait until
late June when the leaves are fully developed to apply a foliar
application of 20-20-20 fertilizer, at the rate listed above.
Organic sources of foliar N could include fish emulsions or kelp
extracts.