||This Month in Ag Connection|
Use of Select Herbicide to Control Fescue Seed Head Development
Tall fescue is the dominant pasture forage in Missouri. Tall fescue has a few drawbacks when it comes to hay quality and pasture. As the plant grows and the seed head develops, the endophyte fungus moves up the plant and concentrates in the head and seed. As most cattlemen know, when the fungus moves up in the plant and the fescue is heavily grazed, the possibility of fescue foot increases.
Missouri cattlemen now have a product to help counter the effects of head and seed development. Select 2 EC herbicide, when applied at the proper rate and time, effectively suppresses fescue seed head development. Missouri has been granted a special Section 18 Emergency Exemption from EPA for the use of Select on fescue. Select can be applied as a spring application when the fescue starts to green up. Depending on the area of Missouri and year, this usually occurs between March 15 and April 15. At 50 to 90% green up, 1.5 ounces of Select 2 EC per acre is recommended. Or if you chose to apply early at 20 to 49% green up, 2.0 ounces of Select 2 EC per acre can be applied. At these rates, seed head formation should be well suppressed. A fall application of Select before fescue goes dormant can suppress fescue seed heads the following spring.
Caution: only one application of Select should be made in one year. Select only suppresses seed development in the current year. If you use Select to suppress head development this spring, next year you can produce a seed crop if you wish.
(Author: Wayne Crook, Agronomy Specialist)
Phosphorus Fertility on Tall Fescue Pasture - Preventing Grass Tetany
Grass tetany is a nutritional disease of ruminants associated with low levels of magnesium (Mg) in forages. This disorder most often affects cows nursing calves while grazing lush, cool season grass pastures. It is most commonly seen in the early spring when cows nursing spring calves have a three fold greater demand for Mg from milk production and cool season grass pastures have yearly low Mg levels. Recent research results in Missouri reveals that soil phosphorous (P) is important in boosting Mg uptake by tall fescue. Phosphorous fertilization of pastures is a good alternative to Mg supplements for protecting against grass tetany and can help increase calf gains.
Although grass tetany can be fatal, unseen hypomagnesaemia (low blood magnesium) in cows is a more common condition. Hypomagnesemia is a precursor to grass tetany. Low blood magnesium affects cow performance and health and leads to low feed intake, lowered milk production, loss of body condition, and decreases gains of suckling calves.
Cattle producers commonly offer mineral supplements rich in Mg in the spring to prevent grass tetany. Unfortunately, there are problems with these supplements such as cost, palatability, poor acceptance, low intake, reliability and potency of the supplements.
Research at the University of Missouri by Tim Reinbott and Dale Blevins in 1991, 1994 and 1997 showed that soils testing higher than 30 lbs of P per acre typically had greater Mg levels than soils with low P. A continuation of this earlier research was a three-year study at the Southwest Center near Mt. Vernon, Missouri on P fertilization of tall fescue. In addition to Reinbott and Blevins, this research was conducted by Ryan Lock, Robert Kallenbach, Greg Bishop-Hurley, Richard Crawford, Jr., and Matt Massie.
There were three treatments repeated three times on fescue pasture testing lower than 7lbs P/A:
The results were judged on:
The results were a significant 0.21 lb. average daily gain (ADG) in suckling calves increase over the Mg supplemented but not fertilized tall fescue and 0.28 lb. ADG in suckling calves increase over the control. The difference between Mg supplemented low P soils and unsupplemented low P soils was an insignificant 0.07 lb. ADG (see Table 1.).
Even though no true tetany resulted, the study revealed that the blood serum values of the cows on the high P soil had Mg levels nearly the same as the cows that received the Mg supplement.
A very interesting side result of the study was that while the test was for 56 days, the calves on the high P soil (during the test) averaged approximately 40 pound more per calf than the control or Mg supplemented calves when they were weaned. While the researchers believe the added weight is due to the volume of milk produced, additional research will be required to identify the factor or interaction of factors responsible for the increased calf weight at weaning.
(Source: Better Crops/Vol. 85 -- 2001, No. 4)
Managing Your Livestock Operation to Reduce Phosphorous Loss
As many livestock producers are aware, the U.S. EPA and USDA are currently working on a joint strategy to reduce non-point source pollution generated from livestock operations. Once the EPA finalizes its rules, the Missouri Department of Natural Resources will make changes to the states rules regulating confined animal feeding operations. While the final rules governing the future of animal production are yet to be written, it is apparent that Missouri will change from regulating the land application of livestock manures based on the level of a nitrogen to regulating manure application based on phosphorous levels.
The change to a phosphorous index for the application of animal manures is largely due to the greater environmental effects that phosphorous has over nitrogen levels when runoff occurs. While phosphorous is not subject to excessive leaching, phosphorous does move through runoff or erosion and even at low concentrations, it can create large algae blooms and excessive aquatic vegetative growth. Aside from being unsightly, this results in crowding out of other more desirable aquatic plants and animals. Algae blooms can deplete oxygen levels in the water resulting in fish kills. Excessive amount of algae can lead to taste and odor problems in the water and in extreme cases algae can produce toxins that are harmful to animal and human health when consumed.
In order to comply with the new environmental rules regarding phosphorous, farmers who have been applying manure based on maximum nitrogen limits will either need to make changes in livestock feed rations, adjust management practices in the land application of livestock manures, or both.
Traditionally phosphorous has been fed
in surplus of the
dietary requirements of animals due to the low bioavailability of plant-based feeds. The
excess phosphorus represents a safety margin to ensure sound bone development as well as
increased animal performance in milk yield and reproductive performance. Studies conducted
by the University of Missouri have shown that by managing dietary phosphorous, the
phosphorus levels in manure can be lowered without jeopardizing animal performance.
Methods of reducing dietary phosphorous include:
In addition to the ration formulations, livestock farmers should also work to reduce feed wastage by animals as this can contribute significantly to the phosphorous that must be treated in the operations manure handling system.
In addition to management of phosphorous in feed rations, farmers should begin now to re-evaluate their management plans for the land application of livestock manure. Due to the lower requirement of phosphorus for plant growth, typically a larger land area will be required for the application of animal manure. The increase in land area required can be accomplished either by increasing the distribution area for the manure on all owned and rented land. If the land base is currently receiving the maximum manure application, create agreements with neighboring landowners to apply manure on their property. If additional adjacent land is not available thus necessitating the hauling of manure, farmers may want to consider the addition of a manure solids separator. A solids separator will remove excess liquids from the manure making hauling more economical. Solids separation of manure also reduces the nutrient concentrations of the liquid that will be applied on site.
The land application of the manure should be at a rate that is required for plant growth. To determine the amount of manure to apply to an area, take the difference between how much phosphorous a particular plant will utilize and the sum of the amount of phosphorous already available in the soil and the amount present in the manure source (application rate = plant needs [amount in soil + amount in manure]). These amounts can only be measured by a nutrient analysis of a soil sample and a sample of the manure. By growing a plant that utilizes a higher amount of phosphorous, the amount of land required for manure application can be reduced. Examples would be alfalfa, corn for silage, and high yielding grasses removed as hay. In areas where soil test phosphorous is already excessively high, farmers should temporarily stop applying manure, grow a plant that can utilize a high amount of phosphorous, and completely remove harvested plant material from the farm site. This will allow the excess phosphorous to be mined off until soil test analysis show that manure application can continue.
While exactly how and when the new environmental rules
affecting the treatment of livestock manure will be enacted, it appears quite clear that
the land application of manure will be limited based on phosphorous levels. Livestock
farmers should begin the transition now to:
(Author: Darin Starr, Ag. Engineering Specialist)
http://outreach.missouri.edu/agconnection/newsletters/is-02-03.htm -- Revised: September 30, 2002