From the Archives
of the Rare Fruit Council of Australia, inc.
by Brian Freeman, Special Research Horticulturist, Division of Plant Industries, Horticultural Research Station, Gosford
Blueberry Production, Part II
Scientific Name: Vaccinium corymbosum
Family: Ericaceae
Bluberry Production (Continued from previous newsletter)
Excessive
N should be avoided as berry production can be reduced. United States
data show that leaf levels of N above 2.1 per cent of dry weight will
reduce production. Balance the amount of N fertilizer against the
number and length of fruiting shoots and new canes growing from the
crowns. The greatest demand for N is when fruit is maturing and when
shoot growth and floral initiation is occurring. If N is low, flower
bud development for next year's crop will be reduced.
Phosphorus (P) and Potassium (K)
If
soil tests and leaf analysis indicate P and K are deficient, readymix
fertilizers such as 10:10:10 (N:P:K) should be applied each spring.
Soils
containing 10 ppm or more of P do not require any more but should be
monitored annually. Soils deficient in P(0-6 ppm) require 15 to 44 kg P
per hectare (equivalent to 161 to 473 kg superphosphate). Soils with
high exchange capacity do not require K if tests values are in excess
of 90 ppm. For low reserve soils, deficiency levels exist at 150 ppm.
Application of K will range from 28 to 84 kg per hectare or 61 to 182
kg potassium sulphate.
Both P and K can be applied together in
the ready-mixed fertilizer described above. If K is not needed. a
16:20:0 mix will suffice. There are many combinations and it is
advisable to consult your local Department of Agriculture advisory
officer for your particular needs.
Calcium (Ca) AND Magnesium (Mg)
Soil
test values of less than 1.5 millliequivalents Ca and 0.25
milliequivalents Mg indicate a need for these elements. If both Ca and
Mg are needed on mineral soils and the pH is 4.0 or less, apply
dolomite (calcium magnesium carbonate) at 500 kg/ha and retest before
further applications. If Ca alone is required and the pH is above 5.0
apply gypsum (calcium sulphate) at 500 kg/ha and retest in a few weeks.
If Mg alone is needed, apply up to 500 kg epsom salts (magnesium
sulphate) per hectare.
A soil test every 3 to 5 years should be
made to ensure the balance between Ca, Mg and K is satisfactory. A
ratio of Mg to Ca of 1.10 and K to Ca of 1.5 is suggested in some
literature but this may vary according to local conditions.
| TABLE 4. Nitrogen rates for blueberry plants* | | Age of plants from transplants | Amount of nitrogen to apply per plant (g)! | Total Kg N/ha per year | | years | Sept./Oct. | Dec. | Jan.# | (2400 plants/ha) | | newly set | ** | 5 | 5 | 24 | | 1 | 3 | 5 | 5 | 31 | | 2 | 5 | 5-10 | 5-10 | 36-60 | | 3 | 8 | 5-10 | 5-10 | 43-67 | | 4 | 11 | 11-17 | 5-10 | 65-91 | | 5 | 14 | 11-17 | 5-10 | 72-98 | | 6 | 17 | 11-17 | 5-10 | 79-105 | | 7 | 20 | 11-17 | 11-17 | 100-130 | | 8 or more | 22 | 18-22 | 11-17 | 120-146 |
* Rates are for mineral soils. On organic soils, normally only the Sep/Oct application is necessary.
!
5 g N=2 level tablespoons ammonium sulphate, or 1 1/3 level tablespoons
ammonium nitrate or 4 level tablespoons 10% N fertilizer such as
10:10:10.
# Nitrogen should be applied after January only if plants need it and only if irrigation water is available.
Source:
C.C. Doughty, E.B. Adams and L.W. Martin. Highbush Blueberry Production
in Washington and Oregon. Washington State University (1981).
Fertilizer application
In
general terms, 1-year-old plants should receive about 50 g of a general
10:10:10:5 (N:P:K:Mg) fertilizer in spring. This amount should be
doubled annually until year 6. Additional N or other elements can be
applied as indicated by foliage symptoms and leaf analysis.
The
fertilizer should be well-distributed around the base of the plant and
watered in. Growers with microdrip or microjet irrigation systems may
wish to inject the fertilizers through the system to simplify
application. A guide to fertilizer application based on leaf analysis
(Table 5) developed for highbush cultivars is useful for Australian
conditions but may be subject to modification. Leaf samples should be
picked when nutrient levels vary the least - probably mid-December in
Australia. Leaves (5 from each of 10 bushes) should be picked from the
fruiting shoots. Select the youngest full-sized leaves - fourth to
sixth nodes from the tip.
Irrigation
Blueberry
plants have shallow, fibrous roots and short periods of drought will
adversely affect growth and production. Peak water demand occurs during
the periods of fruit set and fruit growth. Inadequate watering in the
final 2 to 3 weeks of fruit growth can seriously reduce berry size.
Another critical period is February and March, when floral initiation
for the following crop is taking place.
Inadequate irrigation in
heat wave conditions will result in wilting and dieback of tender
shoots and shrivelling of berries which then drop. Temperatures in
excess of 45°C can be tolerated, provided there is adequate water. A
rule of thumb guide for watering is to allow for 25 mm per week during
the growing season with bursts of up to 38 or 40 mm in the final 2 to 3
weeks of fruit growth. Minimal watering is required in winter and
natural rainfall should suffice. A mature plant requiring this amount
of water would use 100 to 150 L of water a week. This is best supplied
in small amounts on a regular basis. Overwatering that leads to
waterlogged soils creates unfavourable conditions for growth and
predisposes the roots to attack by root rot organisms, particularly Phytophthora
species. Good quality water is essential. Blueberry plants are not
salt-tolerant. A water test is essential to be certain salt levels are
below 300 ppm (0.46 mS/cm).
Where water supply may be limiting,
storage facilities are necessary and a minimum capacity should be 2.2
ML/ha. This will supply sufficient water for approximately 12 rain-free
weeks.
Pollination
Studies
in the United States have clearly demonstrated the value of bee hives
in the plantation to improve fruit set. Three or four hives per hectare
should be adequate. Highbush cultivars, while self-fruitful, will
respond to cross-pollination and should be planted in blocks of single
cultivars. Rabbiteye cultivars require cross-pollination for successful
fruit set. Ratios of 1:1 through to 1:5 of cross-pollinating cultivars
are required.
Pruning
Pruning
is essential to promote strong new wood, increase plant size and
maintain high yields with large berries. Poorly pruned or neglected
bushes become crowded with weak, twiggy growth, produce small berries
and fail to develop strong new wood for future production. Pruning is
traditionally practised in late winter although plants can be pruned at
any time from the end of harvest. During the first 2 to 3 years,
pruning is limited to the removal of older twiggy growth at the base of
the plant and those low branches that are likely to allow the fruit to
lie on the ground. The strong new growth is left. The removal of
flowers from 1-year-old plants will encourage vegetative growth and
generate larger bushes in year two.
Mature plants are pruned to
remove old canes that have no strong new wood, and week twiggy growth.
It is important to prune systematically to make the job easier and to
be sure that production is not lost. First year canes are not branched
and will not produce much fruit in the coming season, but they are very
important for subsequent crops. Fruit is mostly borne on strong
laterals and twigs of second and third year canes. Fourth year and
older wood is not very productive and should be removed. Cut canes back
to the ground or a strong new side shoot. By removing one or two old
canes and allowing these to be replaced each year, no canes will be
over 6 years old.
A guide to pruning is as follows:
(1) Remove any canes damaged by disease, insects or mechanical injury.
(2) Cut out one or two older canes. Choose the least vigorous.
(3) Remove low branches and short, soft new shoots that develop from the crown late in the season.
(4)
Remove weak, twiggy wood from the top and outer parts of the plant. Be
sure sufficient light can penetrate to the centre of the plant. Weak,
twiggy wood produces few flower buds and the berries are small.
(5)
If the plants tend to overbear, tip back the fruiting shoots to remove
about one third of the flower buds. These are the fat buds on the
terminals of the previous season's growth.
Pest management
Weed
Control: Because of the multiple stems that develop from blueberry
plant crowns, problem weeds can become entangled and difficult to
remove. It is therefore very important to prepare the ground carefully
before planting to ensure total weed control. In the first year,
herbicide treatment must be done with caution because the root systems
of young plants are near the surface and easily injured. It is
preferable to delay using herbicides for at least 6 months.
Herbicides
provide selective control of many annual and perennial weeds in
established plantings and several safe and effective herbicides are
registered in the United States for use in blueberry fields. Consult
your local Department of Agriculture advisory officer for the choice of
herbicides in your district.
Mulching with sawdust will assist weed control whilst preserving soil moisture.
| Foliar nutrient levels of blueberries | | Element | Deficiencybelow | Standard Range | Excess above | | Minimum | Maximum | | Nitrogen(N) | 1.70% | 1.80% | 2.10% | 2.50% | | Phosphorus(P) | 0.10% | 0.12% | 0.40% | 0.80% | | Potassium(K) | 0.30% | 0.35% | 0.65% | 0.95% | | Calcium(Ca) | 0.13% | 0.40% | 0.80% | 1.00% | | Magnesium(Mg) | 0.08% | 0.12% | 0.25% | 0.45% | | Sulphur(S) | 0.10% | 0.125% | 0.20% | --- | | Manganese(Mn) | 23 ppm | 50 ppm | 350 ppm | 450 ppm | | Iron(Fe) | 60 ppm | 60 ppm | 200 ppm | 400 ppm | | Zinc(Zn) | 8 ppm | 8 ppm | 30 ppm | 80 ppm | | Copper (Cu) | 5 ppm | 5 ppm | 20 ppm | 100 ppm | | Boron(B) | 20 ppm | 30 ppm | 70 ppm | 200 ppm |
Source:
C.C. Doughty, E.B. Adams and L.W. Martin, Highbush Blueberry Production
in Washington and Oregon. Washington State University (1981)
Disease control
There
is no list of blueberry diseases in Australia due to the lack of
commercial crop experience. A wide range of fungal and viral diseases
have been reported in other countries but, to date, most of these have
not proved troublesome in Australia.
Diseases or potential diseases recorded at Gosford include:
Botrytis twig and blossom blight Phomopsis species in 2-year-old canes;
Guignardia species associated with tip dieback and stem browning;
Botryosphaeria species associated with canker in the United States but no pathogenicity tests made in Australia;
Phytophthora species causing root rot.
There
are control measures available for most disease problems and these can
be discussed with your Department of Agriculture advisory officer.
Insect control
A similar situation exists with insect pests as that described for plant diseases. Those observed in New South Wales include:
painted apple moth (eating dormant buds)
cotton aphid
leaf roller
leaf miner
light brown apple moth
root weevils
small lucerne weevil
Queensland fruit fly has not proved to be a pest, despite large fruit numbers when fly populaions were locally high.
Nematodes
Nematodes recorded as pests in the United States include:
stubby root nematode (Trichodorus christiei)
sheath nematode (Hemicycliophora similis).
Control is only achieved in unplanted ground by fumigation.
Bird control
Birds
can take up to 100 per cent of the crop. Many species of birds feed on
blueberries in the United States, but experience in Australia is
limited. At Gosford, starlings, silver-eyes, finches and the bul-bul
have been observed feedfng on the fruit. All but the bul-bul were
successfully repelled using methiocarb (Mesurol®), an emetic which
discourages the birds from feeding on the fruit.
These sprays
need to be applied every 7 to 10 days from first fruit colour until
completion of harvest. Bird-scaring devices are many and varied, but
need to be carefully assessed before use. These are probably the
cheapest form of control but to be effective, must control birds the
entire time fruit is on the bushes.
Anti-bird netting is
probably the only sure way of achieving full control. This is the most
expensive method but the gain in productivity and quality would off-set
the cost in one or two years. It should be noted that netting will
preclude the use of mechanical harvesters and restrict the operation to
hand-harvesting with harvesting aids. Netting is very light and
requires little support. A plantation can be enclosed at a cost of
approximately $2 to $3 a bush, depending upon the price and quality of
netting. Individual rows may be covered in tent fashion for about $1.50
a bush but vigorous plants will soon entangle the net. The netting
should be installed when the first berries colour and removed after
harvesting is completed. It should be stored in the dark for the rest
of the year to prevent deterioration. The advantage of covering
individual rows is that the same netting can be used for early and late
cultivars, resulting in a significant cost saving.
Harvesting
Harvesting
blueberries by hand is still the best method for collecting top-quality
berries for the fresh market. It is an intensive operation involving
continuous hand-eye co-ordination. A few simple rules which can
increase the picking rate are:
1. Tie or strap a collecting bucket around the waist.
2.
Pick with both hands turned upwards and gently massage the bunches. The
ripe berries are easily removed. In most cases berries turn blue about
a week before they are fully ripe. Do not attempt to remove all of the
blue fruit - just those that come away easily.
3. While transferring
fruit to the container your eyes should be selecting the next bunch.
This way, no time is lost looking for fruit.
By picking this
way, preferably in the cool of the day, it is not difficult for one
picker to remove 10 kg an hour. In the United States trained pickers
can remove 100 to 130 kg a day. The rate of picking is slower on young
bushes and on those in which the fruit ripens over a long period of
time. On most cultivars an interval of 7 to 10 days between harvests is
acceptable and most fruit will be removed in about four pickings. On
mature bushes and particularly those that have concentrated ripening,
the rate, of hand-picking can be very high.
The labour required
to hand-harvest one hectare will vary according to the cultivars
planted. If only one cultivar is planted and each bush has 5 kg of
berries to be harvested in four picks over 4 weeks then each bush, on
average, will yield 1.2 kg. per pick. With 2,400 plants per hectare
each harvest week will produce 2,880 kg. This can be removed over a 5
or 6-day period requiring up to 580 kg. to be removed each day. At this
removal rate, ten or eleven people are required in the field 4 days a
week for 4 weeks.
By shaking the berries into a catching frame,
such as that used in the United States but perhaps modified for use in
Australia, the removal rate can be as high as 350 kg per operator per
day. On this basis, only two operators, instead of ten or eleven would
be needed. An extra field hand or two would be necessary to assist with
the catching frames as would additional fruit sorters to remove the
small amount of unripe fruit, leaves and small twigs that would also be
collected.
The labour requirement may also be reduced by
planting cultivars that ripen over an extended period. Early,
mid-season and late cultivars would extend the harvest from 4 to about
12 weeks with only one third as much fruit being picked weekly. This
would mean approximately 190 kg per day per 5-day week over 12 weeks
and this could be achieved by three or four hand pickers or one person
with a catching frame.
Mechanical harvesters are used in the
United States for farms over 10 hectares. These machines cost about
US$80,000 and remove fruit at rates up to 1,800 kg. an hour. The fruit
loss can be as high as 30 per cent and the fruit is generally only
suitable for processing, although improvements, in the technology of
mechanical harvesting are improving fruit quality and some United
States blueberry farmers are successfully harvesting fruit for the
fresh market with the new generation of harvesting machines.
Harvested
fruit should be quickly removed from the field, sorted, packed and held
in cool storage. Cooling to 12°C is sufficient. Longer shelf life is
achieved if the fruit is held at 1°C to 2°C. The fruit is packed in 250
g punnets sealed with cellophane covers and packed in 12 or 20-punnet
cartons for shipment to market. Freshly harvested fruit may be placed
directly into plastic bags and frozen for later use in cooking.
Marketing
Blueberries
are a new fruit to most Australians and to capture a significant market
it is essential that only good quality, fully-ripe berries are
marketed. Immature blueberries are very tart - something like a lemon.
Supply only the best and the market will grow.
Growers have a number of marketing options for fresh blueberries:
| Direct sale to wholesale or retail distributors. | | Co-operatives.
Fruit is bulked by the co-operative and sold under one label to a
variety of markets. The advantage lies in increased purchasing power
for members and the reduction of price competition on free market. | | Speciality markets such as pick-your-own operations, tourist outlets and the local restaurant trade. | | Export. Best done through a central selling agency such as a co-operative. |
The
Australian Blueberry Growers' Association (ABGA) is establishing a
national marketing strategy. Only through industry unity and
professional marketing on a national scale can growers expect to
maintain good prices for their crop. Information concerning membership
of the ABGA may be obtained by writing to ABGA, 2 Kembla St., Hawthorn,
Victoria, 3122.
Production
Because
of the many factors that affect yield, the productivity of any cultivar
cannot be precisely stated. However, as a general rule the yield in the
second year from planting will be in the order of 1 kg. per bush. This
should increase by 1 kg. per year to 5 kg. per bush in the seventh
year. Production figures in the United States vary widely but yields of
10 kg. per bush are achieved on some cultivars. At the Gosford
Horticultural Research Station, yields from third year plants have been
as high as 8 kg per bush. Berry size is important for both harvesting
and marketing. Large berries are quicker and easier to harvest and are
certainly more marketable. Grading regulations set down by the Michigan
Blueberry Growers' Co-operative prohibit the packaging of berries
smaller than 1.3g for their premier label and 0.9g for their second
grade.
Berry size of recognized cultivars is influenced largely
by plant vigour, pruning and irrigation. Total yield is a function of
overall management and climatic influences.
Back to
Blueberry Page
|
|