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Wild Blueberry Research Reports
Originally published in Plant and Soil 101, 67 72 (1987)
The effects of pruning, fertilizers, and organic amendments
on lowbush blueberry production
P.R. WARMAN
Chemistry-Soils Department, Nova Scotia Agricultural College,
P.O. Box 550, Truro, Nova Scotia, Canada, B2N 5E3
Key words: animal manures, fertilizer,
lowbush blueberry, pruning, soil fertility, tissue composition
A four-year field study was conducted on a Hebert gravelly
sandy loam (pH 4.5) in Nova Scotia to assess the effects of
pruning management and seven fertility amendments on lowbush
blueberry (Vaccinium augustifolium Ait) production
(yield, above ground and root tissue composition) and soil fertility.
Pruning by oil burning produced higher fruit yields than flail
mowing but burning had the opposite effect on the plant N content
(with a lesser influence on above ground Mn and Zn). None of
the fertility treatments (chicken manure, dairy manure, swine
manure, urea, sawdust, NPK, NPK + S + Lime + Micronutrients)
produced fruit yields significantly greater than the control.
Treatments provided the equivalent of 50 kg total N/ha/2-yr
cycle. Treatments influenced tissue N, P, K, Ca, Mg, B, Mn,
Cu, Zn and Mo levels. In general, the three manure treatments
produced the highest levels of plant macronutrients; the urea
treatment produced the lowest levels of plant nutrients. In
most cases, extractable levels of soil P, K, Ca and Mg were
highly correlated with the plant tissue content of these elements.
Overall, the dairy manure treated soils were the highest in
soil fertility.
The lowbush blueberry (Vaccinium augustifolium Ait.)
is one of the leading agricultural crops in Maine and Atlantic
Canada. More than 10,000 hectares of land in Nova Scotia, alone,
is devoted to lowbush blueberry production, with a farm value
of about $4,5000,000/year.
The lowbush blueberry should be pruned following the cropping
season in order to produce good yields for the next crop year.
Pruning is usually carried out in the late fall or early spring
while the plants are dormant. Fruit is not produced on the plants
in the season following pruning, although fruiting buds are
formed, and the plants generally respond to fertilization in
that season. The primary method of pruning the plants is to
burn the fields every second year. Although there are some advantages
to burning, primarily disease, insect and weed control, the
obvious disadvantages include the cost and availability of oil
(the most widely used fuel) and a suspicion that the 2-year
burn cycle has caused steadily declining yields on long-established
fields. Trevett (1956) considered that periodic burning will
eventually destroy the surface organic mat and Al horizon where
most of the blueberry rhizomes are concentrated. The destruction
of this organic mat with the consequent loss of soil organic
matter could have a severe impact on the biological, chemical
and physical properties of the soil and soil-plant relationships.
Flail mowing, therefore, has been introduced as an alternative
management technique (Ismail and Yarborough, 1981).
A soil of high organic matter content is considered a good
site criteria for cultivated lowbush blueberries. Trevett (1972)
suggested mulching new plantings with peat or sawdust or applying
barnyard manure. Trevett (1971) discussed the use of poultry
manure and indicated "barnyard manure may need retesting in
lowbush blueberry production..." Farmers have been reluctant
to use manure on blueberry fields because of the costs involved
with hauling and spreading the manure and the fact that they
are not sure how much to apply. However, given the high costs
at commercial fertilizer and the apparent depletion of soil
organic matter, the use of organic a mendments may yet become
a recommended management practice.
A four-year study was initiated to (a) assess the effects of
various organic amendments and fertilizers on lowbush blueberry
yield and nutrition and on soil fertility, (b) compare blueberry
and soil response to pruning by flail mowing or oil burning.
The results of the first 2-year cycle have been published (Warman,
1985); this paper documents the last two years of the study,
including the accumulative response to pruning and fertility
amendments.
This page and all contents Crown copyright ©
1997, Province of Nova Scotia,
all rights reserved.
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