QUESTION #10 

My alfalfa yields this year are only about half of last year. I've been wondering if I am cutting it right. We had plenty of rain, and the stand is still pretty thick. Maybe I should change varieties. It might be a fertility problem or something else. What do you think? 

EXPLANATION: Cutting frequency, height, date, etc., can vary widely and seldom cause drastically reduced alfalfa hay yields. Poor decisions having to do with variety, insecticide, herbicide, and site selection usually cause stands to thin quickly. 

After a few years stands thin more quickly under low soil fertility. It is likely this stand has not yet reached that point, but will soon. Unfortunately, most producers first suspect factors other than low soil fertility or low soil pH. 

Good alfalfa production for several decades removes large amounts of fertilizer elements from the soil. Many good fields in Oklahoma were highly fertile for several decades after the prairie was first plowed, but soil fertility has slowly declined. With a relatively small decrease in fertility each year, it is difficult to notice that the soil can supply only a fraction of the amount of phosphorous and/or potassium necessary for good alfalfa production. 

Current soil test calibrations predict about 10% yield response when a deficiency of 60 lb/A P₂O₅ is alleviated. For a good field of alfalfa that represents about 1/2 ton/A increased yield. Conservatively, this is $40/A income increase from fertilizer that cost $12 to $15/A to purchase and apply -- cost/benefit ratio of about 1:3. 

Each alfalfa field should be soil tested frequently. Soil testing is the only way to know if (or how much) fertilizer should be applied. It is a good idea (and inexpensive) to check the fertility level every year, even when no obvious problem exists and twice a year when there is a problem. Once the fertility has become limiting, large amounts of fertilizer must be applied every year to maintain high yields. 

RELATED COMMENTS: Low soil pH can be corrected with a single application of agricultural lime before establishing the field; however, it may be necessary to reapply lime after 6 to 8 years of production. 

Soils "severely" deficient in phosphorous or potassium, on the other hand, are more difficult to improve quickly. Even when recommended amounts of these materials are applied before establishment, it will be necessary to apply phosphorous and potassium each year. 

A certain amount of phosphorus applied as fertilizer is absorbed by the soil and is not available for plants. In addition, large amounts of phosphorus and potassium are removed each year in hay. Five tons of alfalfa hay contain approximately 75 lb P₂O₅ and 300 lb K₂O. This amount is removed as part of the hay crop and must be replaced by fertilizer or soil weathering. Soil weathering is a complex process whereby chemically bond minerals are released by the soil. Regular soil testing is the best way of accounting for how well soil weathering restores crop removal of phosphorous and potassium. 

Low fertility and pH have far-reaching effects on alfalfa. In addition to reducing yield and shortening stand life, as noted above, they can exaggerate the effects of pests. Low fertility conditions result in weak alfalfa plants that do not compete well with weeds. Plant stress caused by low fertility coupled with insect infestations can result in losing an alfalfa stand in a short time. In contrast, well fertilized alfalfa plants without insects, compete with broadleaf and grassy weeds very well, resulting in very little weed encroachment for several years. 

OTHER REFERENCES: 

OSU Soil Test Interpretations. 1993. Earl Allen and Gordon Johnson. OSU Extension Facts 2225. 

Southern Forages. 1991. Don Ball, Carl Hoveland, and Garry Lacefield. Potash & Phosphate Institute.    P.O. Box 922149. Norcross, GA 30092-8149. 

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QUESTION #11 

Will I lose my stand if I cut alfalfa before it blooms? 

EXPLANATION: Recommendations on harvest schedules for alfalfa for many years suggested cutting at 10% to 25% bloom. This is a good time to harvest since there is a good balance between forage quality and yield at this growth stage. Blooming signals that root reserves have been replenished and plants are prepared to regrow rapidly without sacrificing vigor. 

Cutting before bloom is essential for reliable production of high quality dairy hay. Research conducted in Oklahoma over the last 15 years indicates that cutting at the bud stage does not severely damage stands. Harvests can occasionally be taken before the plants begin to bud without serious damage; however, repeatedly cutting at prebud may shorten stand life. Frequent cutting at prebud may not allow plants enough opportunity to replenish root reserves between harvests; thus, over a period of several harvests, stand decline may be hastened. 

If cutting often at the prebud stage causes stand life to be reduced by one year, this result in reduced profits because of having to establish a new stand earlier than planned. A premium price must be received for hay to offset the loss of profit due to reduced stand life. Economic analyses of alfalfa forage production indicate that 2 years are needed to recover establishment costs and begin making a profit from alfalfa. 
OSU surveys indicate dairy managers are willing to pay more for higher quality alfalfa hay. In general, dairies will pay $5-$15 more for -- 

• 2 to 5 percentage points higher protein, 
• 5 to 10 percentage points higher TDN, or 
• 15 to 30 points higher RFV. 

Any factor that reduces productive stand life must be offset by increased profitability during the remaining years to keep the entire enterprise operating at a profit. 

RELATED COMMENTS: In Oklahoma cutting at 10% bloom is not a good indicator for determining cutting time of the first crop of alfalfa forage. Weather conditions are often cool and wet enough in Oklahoma to delay blooming. 

A much better indicator is to cut when new crown buds are noted at the base of alfalfa plants. Harvesting at this time results in higher quality hay and reduces drying time 1 or 2 days. If you want high quality hay, therefore, it is important to cut in the bud stage or as soon as crown bud growth begins. 

Timing of first harvest can also be set by the calendar for healthy stands. Vigorous alfalfa stands can be harvested about April 15 in the southern part of Oklahoma and about May 1 in the north. 

OTHER REFERENCES: 

Forage Quality Interpretations. 1993. John Caddel and Earl Allen. OSU Extension Facts 2117. 

Question #13 in this series on forage quality. 

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QUESTION #12 

When I cut alfalfa real short, it seems to take a long time for the next growth to start. What is the best cutting height? 

EXPLANATION: Nearly all regrowth comes from buds in the crown area of the plant. Very little regrowth comes from stems higher than 2" from the soil. 

When a sickle bar or flail knife hits the ground and cuts crowns, plants die or only regrow slowly. This is a good reason to start with and maintain the smoothest field surface possible. The aim should be to cut all stems as short as possible without scalping crowns. 

An important reason for cutting alfalfa short is to remove insect and disease habitat. Most insects, disease organisms, and even dodder (a parasitic weed) need leaf and stem material present at all times. Long stubble left in the field provides a good place for these pests to live until there is enough new growth to support them. Cutting short allows sunlight to reach the soil, killing many microorganisms and some insects. 

Cutting short also allows the soil surface to dry. This drying inhibits germination of certain weed seeds. Another reason for leaving as little stubble as possible is to remove old plant material from the field, thereby keeping it out of the next cutting and improving quality and appearance. 

Fields green up slowly under drought conditions. This is a drought tolerance trait in alfalfa. Plants go dormant but remain alive under extremely dry conditions, essentially avoiding growth during dry periods. Regardless of cutting height, under such conditions fields normally remain brown after cutting for extended periods . 

Fields that are cut high (over 4" above the ground), normally continue to have a green cast after cutting. This is usually old stems and leaves left by the swather. It is not new or normal regrowth. 

Frequently, when harvest is delayed, for whatever reasons, and growing conditions are good, alfalfa plants initiate regrowth from crown buds before cutting. Sometimes this gives the impression of rapid regrowth and can occur independently of cutting height. 

Regrowth from crown buds before cutting signals original stems have stopped growing, and it is (or was) time to harvest. Regrowth from crowns before cutting is most apt to occur when growth stops because of cold weather or very dry conditions. When warm weather returns or it rains, new growth comes from the crown area rather than from elongation of old stems. 

RELATED COMMENTS: We routinely cut alfalfa variety test plots at a height of 2" to 3" with a flail cutter. The harvester creates a little vacuum-action that sucks up leaves and thrash. As a result, the environment is poor for disease organisms and insects. Under good growing conditions, plots are completely green and regrowing rapidly within just a few days. 

When cutting occurs earlier than normal, it may take a week or more for fields to green up with regrowth. The reason for this delay is that plants were not physiologically ready to regrow (not short cutting height), and it takes a few days to activate crown buds. 

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QUESTION #13 

What is the best cutting interval for alfalfa? Should I always cut at 10% bloom? 

EXPLANATION: The traditional response to the question regarding when to cut alfalfa has been, "cut at 10% bloom for the best combination of yield, quality, and stand persistence." However, as the "short answer" implies, there is no single best cutting interval for alfalfa. 

Producers must decide what intervals are most appropriate for their operations and markets. For example, alfalfa cut when less mature (bud stage) may yield 20-30% less forage (Figure 1); however, it will have much higher protein content and relative feed value than that cut at mid-bloom (see Table 1). 

If the higher quality forage can be sold for $15 to $20/ton more compared with lower quality forage, revenues may be greater with early cutting. If there is little or no price advantage for high quality, later cutting and fewer harvests per year will normally be more economical. 

For farmers who plan to consistently cut their alfalfa at bud stage compared with bloom stage, the following considerations are important. Assuming that the first harvest is taken in late April or early May, a total of six harvests are possible on a 28-day cutting cycle if soil moisture is not limiting. The last harvest would be taken in mid-September (Table 2). This cutting schedule would compare with 4-5 harvests taken on the 35 or 42-day interval. Although annual yields may not differ greatly between the cutting schedules, added harvesting costs of $22-$44/A would be incurred with the 28 or 30-day interval. A higher price must be obtained for the forage cut at bud stage to offset these costs. 

OTHER REFERENCES: 

Forage Quality Interpretations. John Caddel and Earl Allen. OSU Extension Facts 2117. 

Question #11 on harvesting alfalfa "early" and the possibility of stand loss. 

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QUESTION #14 

It's mid-July; my alfalfa is 8 to 18 inches tall; it's very thin; but it's blooming in some areas; should I cut it? 

EXPLANATION: Hay yields described in this question would probably be about 1/3 ton/A, which would probably not cover harvest costs. Other options would normally be more profitable. These include: 1) doing nothing for a few weeks; 2) harvest by grazing now; or 3) harvesting seed in late August. 

Why do nothing? Drought-stressed alfalfa is normally poor quality; consequently, this alfalfa stand would produce mediocre to low quality forage this time of year, worth about $60/ton. At 1/3 ton/A, this would amount to about $20/A. Assuming harvesting costs and hauling at $23/A, it is not economical to harvest this as hay for its cash value. (See Table 1.) 

 
If this alfalfa is produced for high quality dairy hay, it may be important to cut it now. Cutting it removes stems that distract from the appearance and forage quality of the next harvest. This assumes another cutting is highly likely. 

Under rain-fed conditions in Oklahoma, predicting whether there will be another cutting in a particular summer is difficult; however, a rule-of-thumb can be helpful. Alfalfa requires about 6" of water in the soil, available to the plant roots, to produce 1 ton of hay/A. If the alfalfa described above is suffering from drought, a normal occurrence throughout Oklahoma each summer, one can assume there is very little moisture available to the roots. What is the probability of receiving 6" of rain during the next month? While it is possible to receive thunderstorms in July with more than 6" rains, these rains normally come hard with a lot of run- off. 

Based on these concepts and probabilities, it is unlikely there will be enough rain during late July and August to produce a good cutting of alfalfa after droughts earlier in the season. The most economical approach may be to give up trying to make high quality dairy hay in this field this summer. So, do not cut the alfalfa. Just leave it and hope it rains at least 2" or 3" during the next few weeks. These rains would allow a cutting of hay near the end of August. Quality will not be high because of drought stress, although it will probably be higher than necessary for most beef cattle or dry dairy cattle. 

Grazing option. Instead of making hay, a better option may be to graze drought-stressed alfalfa in late summer. Grazing is the least expensive way to harvest alfalfa. When alfalfa is droughty in the summer, bloat problems are controllable. During late summer, when alfalfa stops growing, flash grazing can be a very good way to harvest. 

Several advantages and disadvantages of grazing alfalfa are discussed in Question #2. 

Seed production. Another option, particularly in the western half of the state, that should be considered is letting the alfalfa go to seed. Producers can control harmful insects and supply pollinators (usually honey bees) with relatively little cost (less than $40/A). Seed yields of 200 lb/A can gross $200/A. Expenses for threshing, cleaning, and bagging should cost about $100/A. The producer would sacrifice two light hay harvests and clear as much as $100/A from seed production. Seed yields frequently range from 300 to 500 lb/A. 

If dry weather results in low forage yields most years, producers should look seriously at alfalfa seed production as a primary enterprise. The main change that is normally advisable is to harvest hay about May 15. Then, let alfalfa go to seed, initiating bloom about June 15. Seed harvest should be in mid-August. In addition to seed production, two or three hay harvests are possible -- one or two before seed production and one or two after seed production, if moisture conditions are good. 

HARVEST COSTS: The following table estimates harvest costs based on low yield (1/3 ton/A). Note that raking costs are higher than normal because more passes will be made over the field to create windrows large enough for baling. Because there are fewer windrows, estimated baling costs per acre are lower than normal. At 1/3 ton/A yield, the break-even point (between hay value and harvest costs) is approximately $70/ton. Producers should be sure that they can receive $70/ton or more before cutting very low yields for its cash value. 

OTHER REFERENCES: 

AGMACH$ - Agricultural Field Machinery Cost Estimation Software. 1994. R.L. Huhnke and W. Bowers. OSU Oklahoma Cooperative Extension Service. 

Oklahoma Farm and Ranch Custom Rates, 1993-94. Raleigh Jobes and Darrel D. Kletke. OSU Current Report CR-205. 

Pros and Cons of Grazing Alfalfa. C.A. Griffith (Noble Foundation). 1990. Proceedings of the 46th Southern Pasture and Forage Crop Improvement Conference. Overton Texas May 7-10. Pages 90-93. 

Beef Production from Continuously Grazed Alfalfa. Jerry D. Volesky and Daniel P. Mowrey. 1993. Forage and Livestock Field Day. USDA-ARS Grazinglands Research Lab. El Reno OK. Pages 20-22. 

Question # 2 in this series on Guarding Against Bloat.

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QUESTION #15  

What is the best variety for grazing? 

EXPLANATION: Some new alfalfa varieties are marketed as grazing alfalfa. No variety is available that does not cause bloat. Some producers "read into" advertisements or assume that a new grazing alfalfa would be "bloat resistant." No breeder claims to have a bloat-resistant variety. 

A producer interested in grazing livestock on alfalfa in combination with haying should select the best hay-type varieties. In Oklahoma, current reports are published annually with results of alfalfa variety tests. 

In general, good hay-type varieties respond to cutting for hay and rotational stocking in the same way. Continuous stocking of hay-type alfalfas (and probably grazing types) should be managed so alfalfa is not grazed shorter than 6". 

'Alfagraze' was the first variety developed for the south and for continuous stocking during the summer. Alfagraze persists better than traditional hay-type alfalfa in such systems, but its yield in Oklahoma is not as good as the best varieties developed for hay. Animals are allowed to graze alfalfa for up to 120 days in continuous stocking systems. Normally animals are taken off the alfalfa only during very wet conditions when they would track up the fields badly. 

Typical generalized economic treatment of grazing alfalfa makes it look like an attractive option. There is no consistent difference in price of seed between grazing alfalfa varieties and traditional hay types. For the sake of comparing grazing vs. haying, let's assume -- stocker gains of 2 lb/day during 120 days with gains valued at $.30/lb, a 5 ton/A yield and 20 lb/head consumed, resulting in 500 stocker-days/A. Assuming gains of 2 lb/day/stocker, one arrives at 1000 lb of gain/A or $300/A. 

This compares to 5 ton/A of hay at $80/ton resulting in $400/A gross income. Harvest costs of $30/A/cutting for five cuttings leaves $250/A. Generally other production costs are about the same for haying and grazing. This results in a $50/A advantage to grazing alfalfa over haying. 

RELATED COMMENTS: 

Most major alfalfa breeding programs will release "grazing alfalfas" in the next few years. Each new variety will have to undergo systematic evaluation for persistence and yield. 

We currently have two grazing-tolerance tests, both at the Agronomy Research Station at Perkins (just south of Stillwater). The older test was stocked continuously in the summers of 1993 and 1994. The other test was sown in September 1994 and will be grazed until differences among varieties appear. 

After one summer, all stands were still very thick and no difference between grazing-type and hay-type varieties was detectable. At the end of the second summer, all entries in the test had thinned much more than comparable varieties in hay-type tests, but no significant difference between types was evident. 

OTHER REFERENCES: 

Alfalfa Varieties for Oklahoma -- 1994. J.L. Caddel and J.D. Prater. OSU Current Report CR-2106.

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QUESTION #16 

Bale accumulators are heavy when full and compact the soil so much that it hurts the stand; what is the best way to get big bales out of the field? 

EXPLANATION: The jury is still out on soil compaction in alfalfa fields. Rutting is usually the result of poor field conditions, i.e., too wet. It could also be the result of excessive loads for the tire capacity. In either case, flotation tires and/or hauling fewer bales at a time may alleviate the problem. 

If soil depressions are not detectable, then soil compaction is probably not severe enough for concern. In Oklahoma typical soils used for alfalfa tend to be well-drained and not easily compacted by wheel traffic under dry soil conditions. There are, however, two exceptions, both involving swathers using the same tire path for each cutting. 

One situation is the tire path of the first windrow in a field. The second can be observed in fields under center-pivot irrigation where swathers tend to follow the same paths around the field. Even so, this visible decline in plant vigor may be the result of plant damage rather than soil compaction. 

Hauling fewer bales at a time and flotation tires increase production costs. The cost of plant damage from wheel traffic and compaction can be estimated only for individual field situations. Producers should avoid such situations to the extent possible.

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QUESTION #17 

Disk mowers leave alfalfa stems tattered and shredded; how much does this hurt plants by letting in diseases? 

EXPLANATION: Tips of cut stems dry out in just a few hours after cutting. Because disease organisms cannot enter through dry stems, it is unlikely pathogens are entering the plant through cut stems.  

There may be a slightly longer recovery period associated with the disk mowers. This may be caused by late harvesting coupled with disk mowers cutting stems shorter than reciprocating mowers. Most new shoots emerge from the crown of the alfalfa plant. The shorter cutting height with disk mowers might also cut more of the new shoots. Harvesting should normally be done before new shoots emerge form the crown.  

If a producer has a disk mower for another crop, there is no reason to buy a sickle mower for alfalfa.

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QUESTION #18  

Each year I experience problems with caterpillars and aphids in the summer months. How should I manage these insect pests? 

EXPLANATION: Spotted alfalfa aphids and larvae, such as webworms, armyworms, corn earworms and alfalfa caterpillars may be found throughout the summer in alfalfa. Often, damage by these pests goes unnoticed in thick, healthy alfalfa stands, and insecticide application is not profitable. However, when numbers of foliage feeding caterpillars reach 5-6 per sweep or spotted aphids exceed 20-30/stem, spraying may be justified. If alfalfa growth has reached early bud stage or beyond, cutting can be an effective alternative to spraying. The harvest operation will generally kill the majority of caterpillars. Likewise, spotted alfalfa aphid populations are usually killed by the harvest operation. 

Early harvest adds little to the cost of production, assuming there is enough forage (more than 1/2 ton/A) to justify harvesting. In contrast, if forage quantity is insufficient, use of a short residual insecticide, costing approximately $6.00 per acre, should provide adequate control of these insects. 

Benefits would include: 

• saving approximately 50-100 lb of forage per acre, 
• improving forage quality with a better leaf-to-stem ratio, and 
• eliminating the build-up of honeydew from aphids. 

If aphids are severe enough, the entire harvest can be lost, in addition to total stand loss in heavily infested areas. Forage value associated with increased yield and quality would be: 

• $60-70/ton of stemmy hay versus $80/ton (average) of leafy alfalfa. 
• Loss of $2-4/A in forage yield. 

In light of these figures there is at least a $6/A advantage to cutting early where yields justify this approach (based on chemical cost alone). Where yields are insufficient, the $6/A cost associated with chemical treatment far outweighs the estimates of loss ($14-28 per/A) associated with no treatment. Quality losses may be variable; however, as more leaf tissue is lost, protein and relative feed value decrease. 

RELATED COMMENTS: If numbers of aphids or caterpillars are high before cutting, thoroughly scout fields for several days following haying to insure that the insects have been controlled. If insects are damaging regrowth, then an insecticide treatment may be required. Removing the hay before treatment will aid in effective penetration of chemicals into the site. 

OTHER REFERENCES: 

Alfalfa Forage Insect Control. OSU Extension Facts 7150. 

Alfalfa Aphids in Oklahoma. OSU Extension Facts 7184.

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QUESTION #19 

Part of my market for alfalfa involves selling hay to horse owners. What can I do to eliminate their concerns about blister beetles? 

EXPLANATION: Blister beetle contaminated hay is usually the result of beetles being crushed prior to baling. As hay dries, beetles not killed in harvesting will leave. Crushed beetles occur where the swather, equipped with a crimper, cuts hay infested by a swarm of beetles. Remains of beetles may be concentrated in small portions of bales and fed to livestock. Beetles may also be killed in forage that is driven on before they have time to escape. Suggested means of combating blister beetle problems in alfalfa include: 

• Cut hay without using crimpers. This suggestion does not usually interest producers, since not crimping hay increases drying time. 
• Use a sickle bar mower without conditioner, which is generally slower and dose not crimp. 
• Avoid wheel traffic on standing or cut hay. This can be difficult, since even sickle bar mowers often require driving over previously cut hay. If the cut swath can be straddled, this approach is effective. Many mower/conditioners allow the swath to be straddled by subsequent wheel traffic. 
• Cut at or before the 10% bloom stage. Timely cutting of hay in the early bloom stage eliminates flower attractants for adult beetles. 
• Use small square bales for horse hay. This allows for easy inspection of flakes of hay as it's being fed to horses. 

ECONOMIC ANALYSIS: If alfalfa hay is suspected to contain blister beetles, it has no value as horse feed. The cost of proposed mechanical procedures for avoiding blister beetles is difficult to calculate, but is little, unless new or modified equipment is needed. 

Insecticide costs will range from $7-12 per acre. Benefits include being able to sell hay to horse owners with confidence and perhaps less liability insurance. 

OTHER SUGGESTIONS: 

When dealing with horse owners, sell hay harvested before May 15 or after Oct. 15. No specimens of the striped blister beetle have been collected in Oklahoma before May 14. Likewise, fall cuttings (mid-late Oct.) can be harvested with little risk from blister beetles. Unfortunately, insect activity is temperature driven; therefore, warm fall weather may prolong activity of beetles. 

Scout fields before and during harvest. Beetles disperse when encountered, so swarms can be detected just in front of the harvester. Drivers spotting swarms can stop and allow swarms to disperse. This is not a very reliable nor realistic approach because small swarms are hard to see in tall, thick stands of alfalfa. 

Treat hay intended for horse consumption with a short residual insecticide. Unfortunately, only a few compounds are labeled for this use. SevinŽ and Methoxychlor have a seven day waiting period between application and cutting. Therefore, only beetles present during the treatment period will be killed. Migrating swarms may subsequently contaminate hay. 

RELATED COMMENTS: Blister beetle problems are associated with the substance cantharidin. This toxin occurs naturally within the beetles' bodies. Horses are considered most susceptible, with some incidences of toxicity reported in cattle and sheep. The striped blister beetle is the primary concern because of its gregarious (swarming) habits. 

Toxicity of blister beetles to horses is variable due to horse age, breed and general health. The estimated minimum lethal dose is one milligram of cantharidin per kilogram of body weight (see Table 1.). Based on results adapted from Capinera et al. (1985), with 1 mg. of cantharidin/beetle, it would take at least 250 blister beetles to kill a 555 lb. horse and could take as many as 545 beetles to kill a 1200 lb. horse. 

OTHER REFERENCES: 

Blister Beetles and Alfalfa. Phillip Mulder, Richard Shawley, and John Caddel. OSU Extension Facts 2072. 

Cantharidin levels in blister beetles (Coleoptera: Meloidae) associated with alfalfa in Colorado. 1985. J.L. Capinera, D.R. Gardner, and F.R. Stermite. J. Econ. Entomol.

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