The Rural Voice, 2003-05, Page 56Advice
Tips for managing forages in dry years
By Joel Bagg
Forage Specialist, OMAF, Lindsay
Livestock producers are always
aware of the need to put up enough
forage. This can be very challenging
in extremely dry years. Dry weather
creates even more immediate
problems in pasture situations during
the "summer slump". In dry years,
strategies such as rotational grazing
and the use of corn silage can help to
ensure adequate feed inventories.
Forage Yield & Quality — "A dry
year will scare you, but a wet year
will starve you" is an old saying
quoted by some dairy farmers.
Excessively wet years often result in
poor forage quality and problems
getting milk out of cows. In a dry
year, second and third cut yields will
be reduced, but quality is usually
good — no rain damage, high
leaf/stem ratio and reduced fibre.
First cut yields are largely a function
of temperature; whereas second and
third cut yields are more a function of
moisture. Two-thirds of total yield is
typically from the first cut. Severely
drought stressed alfalfa can
sometimes produce alkaloid -like
compounds that may reduce
palatability and intake.
Perennial Forage Species — Alfalfa
is deep rooted and has considerable
drought tolerance, particularly during
shorter periods of dry weather.
Birdsfoot trefoil also has reasonably
good drought tolerance. Red clover
has poor drought tolerance and stands
can be reduced during extended hot,
dry conditions. Timothy, the most
commonly grown grass, has poor
regrowth potential and drought
tolerance. Reed canarygrass has
better drought tolerance and
regrowth, but requires earlier first cut
harvest management.
Emergency Annuals — Cereals,
Sorghum, Pearl Millet, Corn Silage
— By the time you know you're in a
serious drought situation, it is often
too late to do much about it as far as
seeding different crop species. Corn
silage is the most commonly used
annual for emergency situations.
Corn silage is usually cheaper,
readily available, and is easily
52 THE RURAL VOICE
harvested, stored and fed.
Spring seeded cereals need to be
cut by the first week of July for the
boot/early head stage. Warm season
grasses like sorghums and Pearl
Millet can be handled using
conventional haying equipment to
put up haylage. Be aware of prussic
acid risks with sorghums and
sudangrass.
To Harvest Or Not? — Moderate
stress from dry weather can cause
alfalfa plants to reduce stem numbers
and stem elongation. Carbohydrates
produced are stored in the root
system, and are available as energy
for regrowth after cutting and when
moisture returns. If there is adequate
alfalfa growth to economically justify
cutting, and a 30 -to -35 -day harvest
interval can be maintained, go ahead
and cut. Cutting alfalfa after rains
return will stimulate regrowth,
particularly at the flower stage, by
encouraging growth of new crown
buds.
On the other hand, cutting red
clover during drought conditions can
cause stand reductions. Birdsfoot
trefoil also maintains lower levels of
root carbohydrates during the
summer, so cutting at a more mature
stage with longer stubble, will
improve regrowth potential.
Potato Leafhopper Control — The
significance of Potato Leafhopper
(PLH) damage in alfalfa is greatly
underestimated. PLH damage is often
blamed on the hot, dry weather that
accompanies it. PLH feeding affects
the transportation of fluids and
nutrients in the plant and
significantly worsens the effects of
dry weather. New seedings are very
susceptible. Once the symptoms of
"hopperburn" are noticed, the
damage is already done. PLH can be
managed by scouting and spraying at
threshold levels, and by the use of
PLH resistant varieties.
Summer Seedings Higher Risk —
Early spring seedings are usually the
most successful. Late spring seedings
can be severely affected by dry
weather. Summer seedings often fail
when seeds germinate and then starve
for moisture during extended dry
weather. Delayed germination can
result in inadequate growth before a
killing frost in the fall to ensure
winter survival. Lack of moisture is a
risk, so if soil conditions are
extremely dry with no rain in the
forecast, consider abandoning your
plans for summer seeding.
Avoid Critical Fall Harvest Period —
Cutting alfalfa during the six-week
Critical Fall Harvest Period (refer to
Publication 811, Agronomy Guide) is
not recommended, but sometimes
done because of low forage
inventories. This results in the plants
using 'root reserves for regrowth and
increases the risk of winterkill. The
highest risk time to cut is three weeks
after the start of the Critical Fall
Harvest Period, so avoid this time if
possible. Leaving more stubble to
hold snow and adequate soil K
fertility will also help.
Drought Damaged Corn Silage —
Tremendous variation can occur in
drought stressed cornfields. Some
fields will have short plant height
with more normal ears. Yields will be
reduced, but forage quality may be
close to normal. Other fields will be
more normal in height but have very
small ears or no ears. Growers
attempting to salvage drought
damaged cornfields by harvesting
them as forage should be aware of
some of the harvesting and nutrition
implications. Ensiling at the correct
whole plant moisture is critical, but
often more difficult to determine.
Be aware of the potential for
nitrate poisoning. Nitrates
accumulate in corn plants and grasses
when there is a large amount of soil
nitrates, and a lack of moisture that
interferes with normal plant growth.
Nitrate accumulation is often greatest
following a rain that ends a dry
period. The increased nitrate
potential also increases the risk of
silo gas.
For more information, there are
several articles on the OMAF Forage
Website http://www.gov.on.ca/
OMAFRA/english/crops/field/forage
s.html or by contacting the OMAF
Agricultural Information Contact
Centre at 1-877-424-1300.0