PAGE 10 - The Malakoff News - Friday, June 23, 2006
Besides the effect of re-
duced production due to lack
of moisture, drought also cre-
ates other negative aspects for
cattle and hay producers.
Warm-season annual
grasses, such as forage sor-
ghums, sorghum-sudan hybrids
(haygrazer types), and the
various mullets can also accu-
mulate nitrates to a level that
is toxic to cattle during periods
of dry weather. Typical nitrate
accumulation occurs with ex-
cessive N fertilization followed
by a period of drought, although
toxic levels of nitrates have
been observed in warm-season
annual grasses with as little as
50 lbs. of N/ac under drought
conditions.
While aboveground plant
growth is reduced, nitrate up-
take continues to occur and
concentrates in the forage tis-
sue. Ruminants are affected
because microbes in the rumen
are able to convert nitrated to
nitrite.
NLtrite is then absorbed into
the bloodstream where it con-
verts hemoglobin, which car-
ries oxygen throughout the
bloodstream, into methemoglo-
bin, which does not carry oxy-
gen. Cattle death is due to as-
phyxiation.
The total level of nitrate in
forage will determine whether
or not the forage is safe to
feed. Remember: Nitrate lev-
els in hay do not diminish with
time!
Nitrate levels, however, in si-
lage, may be reduced by 50
age, hay, or silage
is safe to feed to
livestock.
Nitrate levels of
5000 ppm or
greater may be
dangerous to feed
animals and
.-- .-- 2 ~
Rick Hirsch
greater than 15000 : :: genus Sorghum
ppm are toxic to i can produce prus-
most classes ofi Agriview sic acid following
livestock, i light frosts or
The official drought.
Texas A&M University advi- In well-cured hay crops,
sory is to not feed forages that prussic acid is not a concern
contain greater than 10,000 since volatilization of the com-
ppm nitrate, pound into the atmosphere oc-
Then more conservative curs during the field curing pro-
number of 5000 ppm, however, ce s s.
may be a much safer number Cattle, however, may suc-
to use in actual practice, cumb to prussic acid poisoning
Producers using warm-sea- while grazing if plants have
son annual forages or been subjected to drought
johnsongrass should have their stress.
hay crops tested prior to har- Again, do not turn cattle into
vesting. Look at the forages pastures of drought-stressed
carefully, sorghums or johnsongrass.
If the forage to be harvested Wait until better growing
for hay has been under drought conditions before pasturing
stress, there is a good likelihood cattle on any stressed warm-
that it is high in nitrates, season annual plant or
If a good precipitation event johnsongrass.
occurs and plant growth isMillets, while still capable of
reinitiated (good green color, no accumulating nitrates to a toxic
droopy leaves), then the for- level, do not produce prussic
age may be safe to feed, but a acid.
forage analysis for nitrate Pond ponderings
would still be advisable.
Do not harvest the forage
If nitrate toxicity many small fish survive They will not reproduce in the
was not enough to (overpopulate) and predators pond, will not muddy the pond
worry about, there become thin because they are like common carp, will not dis-
is also the issue of not able to prey on the forage turb the nests of other fish, and
prussic acid (hy- species. Large growths of they consume 30 to 40 percent
drogen cyanide) weeds also remove nutrients, of their body weight in weeds
i poisoning. Forages which reduces algae produc- every day during warm
i belonging to the tion(food), weather.
Aquatic weeds can be con- The use of grass carp is
trolled by manual, chemical regulated by the Texas Parks
and biological means, and Wildlife Department. Con-
Manual control of species tact the Department or your
such as cattails is practical county Extension office for in-
when they first start to colo- formation on required permits,
nize a pond. Woody vegetation stocking rates and lists of avail-
along the dam also can be con- able sources.
trolled manuaUy. One common problem in
Chemical control with her- Texas is pont "turn-over."
bicides is possible but few her- Turu-overs occur when ponds
bicides are approved for are stratifies; that is, surface
aquatic use and the type of water is warmer than the wa-
aquatic vegetation must be ac- ter below and the two layers
curately identified before it is no longer mix. This caused the
treated. Herbicides can kill cooler water near the bottom
planktonic algae, which leads to stagnate and become de-
to oxygen depletion, pleted in oxygen. Fish avoid
Oxygen depletion after her- this layer of water.
bicide treatment is particularly A turn-over occurs when the
common in hot weather, if the warm upper layer suddenly
pond is heavily infested with cools and mixes with the stag-
weeds, or in both conditions, nant layer.
Check with a fisheries biolo- The two layers mixed to-
gist or your count Extension gether may not have enough
agent for plant identification in- oxygen to support fish and
formation and current herbicide they die. This usually occurs
recommendations. When using after a cold, hard rain.
chemical pesticides, protect If a turn-over occurs, quick
aeration may save the fish.
Similar fish kills also can be
Aquatic weeds are a com- yourself and others by strictly
mon problem in farm ponds, al- following all label directions.
and then test! To do so could
wind up costing you time, ef-
fort, and money and result in a
hay crop that you will not be
able to feed. Likewise, cattle
should not be pastured on
though some aquatic vegeta- A simple and economical caused by oxygen depletions
tion might be good for the pond. long-term aquatic weed con- from a bloom die-off or rotting
Rooted aquatic vegetation does trol method for aquatic weeds vegetation from herbicide treat-
provide habitat for small such as duckweed, hydrilla, ment.
aquatic animals, which adds to pondweed and milfoil is to Question of the week
the food chain. stock sterile triploid grass carp. Q. My yellow squash
panied by a twisting or mot-
tling of the leaves. What
could possibly be causing
this problem?
A. Your plants have been af-
fected by a virus disease, most
often squash mosaic virusI or
cucumber mosaic virus.
This virus is transmitted to
your plants by insects which
have been feeding on other
viru-infected squash plants or
perhaps some wild plant. Once
the plant gets this disease noth-
ing can be done.
Best preventive measures
include insect control and
planting varieties which will
mature early in the year.
This disease is more severe
on late-planted squash or sum-
mer-planted squash than it is
on the early spring-planted
crop.
The green squash (which
should be yellow) is still good
to eat if harvested at the
proper stage of maturity.
There will be little change in
taste. This virus disease will
eventually kill the plant.
Important dates
June 19-20 - District 5 4-
H Horse Show- Henderson
County Fairpark Complex
June 24-25 - FARMEDIC
Training - Trinity Valley Com-
munity College
June 27 - Horticultural
Field Day - Overton
July 78 - Hunter Educa-
tion Course - Texas Freshwa-
ter Fisheries Center
To pre-register, contact Jim
Parker at 903-489-2937 or
percent or more, but may still warm-season annual grasses Vegetation also provides The grass carp, or white amur, plants are doing a peculiar jpparker3@earthlink.net
be excessive for safe feeding,or johnsongrass if conditions small fish with places to hide is an Asian carp brought to this thing. Toward early to mid- Rick Hirsch is the
Only a forage analysis for are suchthatnitratelevelscould from larger predators. The country, f or aquatic weed con- summer the plants which Henderson County Extension
NITRATE (currently $5 at the be elevated to a toxic level, problem with weeds is uncon- trol. once produced yellow fruit Agent - Agriculture for Texas
Texas A&M University SoilAgain, only a forage analy- trolled growth. Grass carp consume vegeta- start producing green or of- Cooperative Extension. Visit
Testing Lab) will determine sis can determ~~a.~e~~ tf~too~ma~y,~l~llelp4Ue tion alm~t ex~rd,y,gfter ten yellow and green fruit, our web page at http://
whether or not the fresh for, i.s,s e to graz "
they r " ',-;rlais is generally aceom- h tcFson'eo tamu.edu.
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