September 6, 2013 15:21
It may be hard to believe with the current warm temperatures but the first fall frost is lingering. After a first frost, there are concerns about nitrates in forage and other livestock feeds. So what are nitrates anyway, where do they come from and why can they be a concern in a feeding program?
Plant roots take up nitrogen from the soil in the form of nitrate (NO3). The nitrate is transported into the leaves where it is converted into protein. Immature plants usually contain more nitrate as they are still growing rapidly. Annual forage crops like oats and millet also normally contain more nitrates compared to perennial forages. Alfalfas, vetches, trefoils, peas and clovers generally do not accumulate nitrates. Under normal growing conditions, nitrates are continuously taken up and converted to protein to fuel plant growth and seed production.
Nitrates can accumulate in a plant following a sudden interruption of growth such as after a frost. The root system is often not affected by a fall frost and continues taking up nutrients from the soil which includes nitrates. As nitrates are being pumped into the plant, the aboveground tissue is not able to process those nutrients and hence nitrates can start to accumulate in stems and leaves. The highest accumulation typically occurs two to three days following a frost. Nitrates will decrease 10 to 14 days after the injury if the plant was not killed and is able to resume growth. If a plant is killed during a frost, the nitrates have no place to go and will remain in the plant tissue. To conserve forage quality it is best to harvest the forage crop within one day of damage. Forage should be tested to know how much nitrates it contains and to be able to adjust the feeding plan accordingly.
The nitrates themselves are not toxic to livestock. However, in ruminants such as cattle, sheep and goats, the rumen bacteria convert nitrate to nitrite (NO2). Nitrite is then converted to ammonia. Nitrate poisoning occurs when the conversion of nitrate to nitrite exceeds the animals’ capacity to convert nitrite to ammonia. Nitrite causes toxicity by reducing the capability of blood to carry oxygen which leads to internal suffocation of the animal. Sub-lethal doses may result in loss of appetite, reduced milk production, slow growth, and abortion.
For more information please contact me at the Watrous Ministry of Agriculture office 306 946-3219, call the Agriculture Knowledge Centre at 1-866-457-2377 or visit our website http://www.agriculture.gov.sk.ca/.
by Nadia Mori
Regional Forage Specialist
September 3, 2013 11:39
Can you identify this plant? Do horses eat it?
Plant sample cut in hayfield
Plant samples in garden, yard and hayfield
Photo credit: HorseOwnerToday.com
August 23, 2013 16:21
Photo credit: Bonnie Newton
Alfalfa field, one month after first cut.
If not properly managed, alfalfa can suffer winter injury or winterkill. Several factors play into good winter survival of your alfalfa stand.
Taking a Second Cut
For alfalfa, early fall is a critical time as plants are storing nutrients needed to survive the upcoming winter. Cutting plants during this period adds double the stress to the plants as they have to expend energy for regrowth as well as nutrient storage. During a minimum of six weeks after cutting, alfalfa plants need good growing conditions to ensure sufficient regrowth and energy storage to support winter survival. Plants harvested after August 15th may not have six weeks before a killing frost and may be susceptible to winter kill. A killing frost is considered minus five degrees Celsius or lower. Harvesting after a killing frost does
not affect food reserves but reduces the amount of stubble which helps trap snow. The trapped snow provides an important insulating blanked for alfalfa crowns.
If alfalfa makes up 50% or more of the production in the stand and was properly inoculated at seeding, nitrogen is generally not a concern in the forage stand as the alfalfa will fix the nitrogen required by the stand. Phosphorus, potassium and sulphur are the three nutrients which should be considered in stands with large proportions of legumes. Phosphorus and potassium are particularly important as they support root and nodule health and over-wintering capability. Both of these nutrients can be fall applied as they are relatively immobile in the soil and will not leach or volatilize to the atmosphere like nitrogen. The most cost-effective way to maintain adequate soil fertility is to do a fall soil test.
An otherwise healthy stand can be impaired by insects and disease such as alfalfa weevils and downy mildew. Scouting for insects during June is important in noticing and minimizing insect feeding damage while disease resistant alfalfa varieties are your best defense against various root and leaf diseases.
Not all factors in alfalfa fall management are under your control. For example, wet soil conditions in the fall can reduce the plants ability to harden prior to winter. Lack of snow cover is also a concern as alfalfa crowns can be exposed to extreme cold. Snow cover can be improved by leaving sufficient stubble height.
Planting cold tolerant and disease resistant varieties along with a good fertility program and careful cutting management will help winterize your alfalfa stand for better longevity and productivity.
For more information on this or other topics please call me at the Watrous Ministry of Agriculture office (306) 946-3219, the Agriculture Knowledge Centre at 1-866-457-2377 or visit our website http://www.agriculture.gov.sk.ca/
September 14, 2012 12:19
Chelsey Carruthers, M.Sc., AAg
Regional Livestock Specialist, Saskatchewan Ministry of Agriculture
Every fall with the first frost looming, livestock producers worry about nitrate in their forages. What is nitrate, where does it come from and what can you do about it?
What is nitrate?
During normal growth, plant roots take up nitrogen from the soil in the form of nitrate and the plant converts it to protein. When plant growth is stopped by an event such as hail, frost, drought or chemical damage, this normal process is affected and nitrate accumulates in the plant.
When ruminant animals eat plants containing nitrate, their rumen microbes convert it to nitrite, which is much more toxic. At low levels, nitrite is handled by the rumen microbes and used for protein production. However, at high levels, the microbes can’t keep up. Nitrite is absorbed into the blood stream where it can cause problems by decreasing the oxygen carrying capacity of the blood. Animals can die due to lack of oxygen. Symptoms of nitrate poisoning include trouble breathing, weakness, diarrhea, muscle tremors and death. At lower levels, nitrate poisoning can cause decreased productivity and abortions.
How can you tell?
Nitrate accumulates in the stems and leaves of plants following periods of stress. However, not all plants are equally affected. Nitrate tends to accumulate in annual forages, such as those used for swath grazing and green feed, and some weeds, and is usually higher in immature plants. Legumes such as alfalfa rarely accumulate high levels of nitrate. Crops that have been fertilized with nitrogen will be at higher risk of nitrate accumulation.
After a stress that kills the plant, such as a hard frost, the crop should be harvested as soon as possible. The plants will not recover, and cannot clear the nitrates. Because the plant roots will continue to absorb nitrate from the soil for a few days following plant death, the nitrate level in the plant will continue to rise during this period.
If the stress to the plant has been mild enough for the plant to recover and continue to grow, harvest should be delayed about ten days. This will give the plant a chance to use up the stored nitrate and convert it to protein.
If you suspect your harvested forage is high in nitrate, a feed test can be done to determine the nitrate level. This will give you an idea of what you are dealing with, and what you can do about it.
What can be done?
Not all frozen forages will be high in nitrate. Testing is the only method for determining the nitrate level and developing a plan to deal with high nitrate feed. Most of the time, the risk to livestock can be decreased by diluting high nitrate feed with low nitrate feed. Water can also be high in nitrate, and should be tested as well. A combination of feed and water both high in nitrate can be a more serious problem. Livestock should be maintained in good body condition, and provided with a diet well balanced in energy, protein, vitamins and minerals. Livestock should also be introduced to higher nitrate feeds very slowly, and monitored carefully.
Understanding the process of nitrate accumulation, the risk factors, and the importance of feed testing can help you to plan ahead and deal with high nitrate feeds to protect the health and productivity of your livestock.
For more information on this or other topics please call me at (306) 946-3237, the Agriculture Knowledge Centre at 1-866-457-2377 or visit our website: http://www.agriculture.gov.sk.ca/
May 25, 2012 12:58
Nadia Mori, MSc, PAg, Regional Forage Specialist
Watrous Regional Services Office
Saskatchewan Ministry of Agriculture
Integrated pest management (IPM) is a well established practice in crop protection and can be a valuable approach in forage stand management. IPM means to have a well rounded weed and pest control plan which considers at all options from prevention to control methods available. The following components should be part of an IPM approach:
1. Monitor Weeds
Monitoring is the process of regularly inspecting pastures to determine if any undesirable plants are present. Scouting also identifies conditions which could favour the development of a weed infestation. For example a recently flooded area on a slightly saline soil may start to convert to foxtail barley.
2. Pest Identification and Biology
Correct pest identification is necessary in order to select appropriate and effective control measures. Consult with an agrologist or biologist if you are unsure about the identification of a weed or insect found in your pasture. Some basic understanding of the biology of the pest is also critical to effective control and prevention. For example, since annual weeds reproduce by seeds, control measures will be more effective if done before seeds are produced.
3. Weed Control
Weed control measures must be evaluated in order to select the most appropriate control measures and combine control methods effectively. Herbicide application is one form of control but other alternatives like providing rest during the growing season, mowing, targeted grazing, burning, biological controls and even hand rouging should all be considered. Each control method will have associated costs and make some solutions more economical. For example, cost of weed control procedure, cost of lost production, and cost of damage to non-target plants are some costs to be considered.
4. Evaluate Weed Control
Control measures must be evaluated to verify the degree of effectiveness. If adequate control has not been achieved, the reasons for the lack of effectiveness should be identified and corrected. Effects on non-target plants and impacts away from the target area must also be identified.
5. Recordkeeping and Program Management
A complete and accurate set of records is basic to any pest control program. Records will assist in identifying key information such as: which pests have been a problem; where the infestations occurred; how successful different control options proofed to be; what the actual cost of the chosen control option was; during which conditions control options worked or not; which conditions allow certain pests to become a problem (for example, site disturbance, drought conditions, or overgrazing).
For more information, please contact:
Watrous Regional Services Office (306-946-3220),
Agriculture Knowledge Centre (1-866-457-2377) or
Visit our website at www.agriculture.gov.sk.ca.