Crop Profile for Alfalfa in Tennessee

Prepared: February, 2005

 

General Production Information

Production Facts:

Production Regions :
Several counties in Tennessee produce pure alfalfa stands with the majority often having dairy herds. Some of the larger production areas include: Giles, Greene, Lawrence, Lincoln, Marshall, Maury, Robertson, Rutherford, Sumner, Warren, Washington, White, and Williamson counties. Alfalfa is often mixed with other forages such as clovers and orchardgrass.

Cultural Practices :
Establishing a good stand is a key factor in obtaining high returns with alfalfa production. Several factors for establishing a good stand are listed below.

 

 

Worker Activities

Alfalfa production in Tennessee is heavily mechanized. Worker activities in alfalfa include field preparation, planting, nutrient and chemical application, pest monitoring, and harvest. Most of these activities are conducted by growers, family members involved with the farm, or their employees. Custom nutrient and chemical applications by commercial dealers and cooperatives are also common in Tennessee. Because of the infrequent need for workers in alfalfa, Re-Entry Intervals (REIs) have little impact on scheduling of field activities. Monitoring for pests, weeds, and diseases may necessitate entering fields soon after the termination of REIs. These activities are generally conducted by consultants, growers or their family members. Activities that bring workers in direct contact with alfalfa during the growing season are generally limited to harvest, especially the loading of rectangular bales for transport to storage or sale.

Varieties Recommended for Tennessee Producers During 2003 and 2004.
Aggressor, Alfagraze, Cimarron VR, Fortress, Gem and Pioneer 5454. Each variety has resistance to Phytophthora root rot with Aggressor, Fortress, Pioneer 5454 having the highest levels.

 

 

Insect Pests

There are various insects which may be found feeding in alfalfa stands across the state. The most common pest is the alfalfa weevil which is one of the first noticed pests. Another pest is the pea aphid which may appear in spotty populations across infested fields. The potato leaf hopper is another common pest which causes hopper burn. Efficacy of pesticides used in alfalfa production are listed in Table 1 and estimated losses from commonly observed pests are listed in Table 2. Average costs of application are listed in the insecticides section of this document.

 

Alfalfa weevil
( Hypera postica )

Adult weevils feed on foliage and lay eggs in stems of alfalfa plants throughout the winter. As weather warms, eggs hatch and larval feeding begins. Small larvae feed within plant terminals, while large larvae often feed in more exposed locations on plant leaves. Greatest effect of damage occurs in the first cutting in March to April; however, lowered stem densities and reduced plant growth may cause lower yields in the second cutting and may ultimately reduce stand longevity. Losses can be a great as 50% yield reduction. Losses usually average around 20 % each year for this pest.

Chemical controls commonly available for adults:

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Chemical controls commonly available for larvae :

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Biological controls:

NOTES : growers are encouraged to scout the alfalfa closely to observe for the presence of any biological controls. High populations of these may assist in controlling many of the pest observed in alfalfa, therefore possibly eliminating pesticide application.

Non-chemical pest management tools:

 

Potato leaf hopper
( Empoasca fabae )

The potato leafhopper (PLH), feeds on over 100 cultivated and wild plants including alfalfa, clover, eggplants, strawberries, some garden flower varieties, potatoes, soybeans, and snap beans. It will typically achieve high populations in late May to early June.

PLH adults are lime green, slender, small (1/8" long), and somewhat wedge-shaped with heads that are slightly broader than the rest of their bodies. They usually have 6 small white dots directly behind their head that can be seen with magnification. The nymphs look similar to the adults except that they are smaller, wingless, and paler green. Both the adults and nymphs are very active. Nymphs develop between 54 to 88 F, with development most rapid at 86 F. They migrate from the southern United States on wind currents and start arriving in the in mid to late March. The females, often fertilized, are usually the first to arrive. Large populations continue to migrate through May and early July. PLH lays eggs in the stems of susceptible plants. Each female lays 2-3 eggs per day and continues to oviposit for at least a month and up to 50 days. Eggs hatch in 7 to10 days. Nymphs molt five times from 1st instar to adult in about two weeks. Nymphs feed primarily on the underside of the leaf. Given their limited mobility, nymphs are considered more damaging than adults. There are usually three generations per year in Tennessee. However, because of the long oviposition period, infestations usually consist of overlapping generations. PLH have piercing-sucking mouthparts with both adults and nymphs causing damage on beans. When they insert their mouthparts into the water and food conducting tissue of plants, they also inject saliva and create physical damage that plugs the vascular tissue. Sometimes, the damage is a characteristic v-shaped brown area at the leaf tip that is called hopperburn. In addition, other damage symptoms include stunted growth, shortened internodes, and fewer flowers and pods. Proper identification of the source of the damage is important for making management decisions.

Chemical controls commonly available:

Organophosphates:

Carbamates:

Pyrethroids:

Non-chemical pest management tools:

 

Aphids, pea aphid
(Acyrthosiphon pisum, and others)

Aphids extract sap from the terminal leaves and stem of the host plant. Their feeding can result in deformation, wilting, or death of the host depending upon the infestation level. Plants that survive heavy infestations are short and bunchy with more lightly colored tops than those of healthy plants. Wilted plants appear as brownish spots in the field. Moreover, plants are often coated with shiny honeydew secreted by the aphids, and cast skins may give the leaves and ground a whitish appearance. These aphids also transmit the pea enation mosaic (not observed in TN) and the yellow bean mosaic viruses.

Wingless, female aphids continue to feed and breed throughout the winter months. In spring, feeding activity increases. At this time, some winged aphids develop and migrate, usually to peas. Most of the progeny of these winged females develop into wingless females. Whenever overcrowding occurs, more winged aphids appear, migrate to different areas, and establish new colonies. Each adult female gives birth to 6 to 8 nymphs each day until she has produced about 100 offspring. Nymphs mature into adults in 10 to 14 days. Since generations overlap and reproduction continues all year, the number of annual generations is difficult to determine. The pea aphid thrives best and reproduces most quickly at temperatures around 65 degrees F (18 degrees C) and humidity near 80 percent.

Chemical controls commonly available:

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Alternative Pesticide:

Biological control:

Non-chemical pest management tools:

 

Blister beetles, black, margined, gray and striped
(Epicauta pennsylvanica, E. pestifera, E. fabricii, E. occidentalis)

Blister beetles usually infest alfalfa fields in mid to late summer. These pests rarely cause economic damage to the alfalfa plant. However, the pest contains a caustic agent known as cantharidin. Cantharidin can cause severe injury and/or death to horses if consumed.

Chemical controls commonly available:

Carbamate insecticides:

Alternative Pesticide:

Non-chemical pest management tools:

 

Threecornered alfalfa leaf hopper
(Spissistilus festinus)

Threecornered alfalfa hoppers girdle stems by their feeding and egg-laying activities. Nymphs and adults weaken the lower stem by piercing it with their needle-like mouthparts and extracting plant juices. As a result, lodging and breaking usually occur weeks after attack. There is some evidence that if damage is randomly scattered and occurs before bloom, in an optimum stand, reduction of at least 25 percent may be necessary to reduce yields. Therefore, these pests rarely cause economic damage.

They overwinter as eggs in plant tissues or as adults protected by clumps of grasses. Young nymphs from overwintering eggs and overwintered adults begin feeding on weedy plants along field borders in the spring. During May or June, they migrate to soybean seedlings. Females then deposit 30 to 40 eggs, singly, in host plant stems. On the average, 50 days elapse between egg deposition and adult emergence. The adults are strong flyers and readily migrate to new fields. Although the biology of this pest has not been studied in Tennessee, there are probably at least two generations each year.

Chemical controls commonly available:

Non-chemical pest management tools:

 

Cutworms,
Black cutworm ( Agrotis ipsilon)
Variegated cutworm ( Peridroma saucia)
Granulate cutworm ( Feltia subterranean)

Many cutworms prefer wilted plant material and sever the plants sometime prior to feeding. Stems are chewed near the soil. Some cutworms climb the host and feed on unopened buds. Cutworms are caterpillars that feed on the stems and leaves of young plants and often cut them off near the soil line, hence their common name. Although there are many important species of cutworms, the black, granulate, and variegated cutworms are the ones most commonly encountered. Each cutworm differs slightly from the others in details of habits and appearance, but their life histories are generally similar. Adults and larvae are nocturnal and hide during the day but may become active on cloudy days. The overwintering forms of cutworms occur in the soil either as pupae or mature larvae. In the spring, the hibernating larvae pupate. Adults begin to appear in the middle of March. Female moths deposit eggs singly or in clusters, and each female can lay as many as 500 eggs. Under optimum conditions, the eggs hatch in 3 to 5 days, and larvae develop in 3 to 4 weeks passing through 6 instars. Pupae mature in 2 weeks during the summer and as many as 9 weeks in the fall. Some of the cutworms can produce as many as four generations each year.

Chemical controls commonly available:

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Non-chemical pest management tools :

 

Grasshoppers
( Melanoplus spp.)

Grasshoppers feed on the leaves of alfalfa, therefore reducing the foliage on the plant. Populations vary from year to year and field to field. Populations are normally higher when the field is surrounded by weedy field borders.

Chemical controls commonly available:

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Alternative pesticide:

Non-chemical pest management tools:

 

True armyworm (Pseudaletia unipuncta)
fall armyworm (Spodoptera frugiperda)
beet armyworm (Spodoptera exigua)

Armyworms are a greater problem during spring and early July, after which time, natural controls keep the population below threshold level. Armyworms feed primarily at night and remain hidden in ground litter by day. They may be particularly numerous following a cool, wet, spring which tends to limit the suppression by natural controls. In contrast, fall armyworms are usually a problem later in the season (July to September), after the moths have migrated northward into the state from the Gulf Coast area. Also, the larvae are active day and night. Parasites and disease organisms will often keep fall armyworm populations in check. However, extremely hot and dry conditions reduce the activity of the fall armyworm's fungal pathogen and promote larval activity. Armyworms prefer grasses, however they can also cause significant damage to young alfalfa. Fall armyworms are somewhat more difficult to control than true armyworms, but all species have the same treatment threshold of five larvae per square foot or 10% damaged foliage. Threshold on young alfalfa may be lowered to 2-3 larvae per square foot.

Chemical controls commonly available:

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Non-chemical pest management tools:



Table 1. Efficacy of pesticides used in alfalfa production.

Pesticide/
Control
PEST
Aphids Alfalfa
weevil
Alfalfa
caterpillar
Threecornered
alfalfa
leafhopper
Potato
leafhopper
Cut-
worms
Army-
worms
Grass-
hoppers
Blister-
beetles
Webworms
Methyl
parathion
G G G G G N G G G G
Azinphos-
methyl
G G G G G E E E E G
Chlorpyrifos G G G G G G G G G G
Phosmet -- -- -- -- -- -- -- -- -- --
Dimethoate G N N N F N N N N G
Carbaryl F G G G G G G G G G
Methomyl F G G G G N G G G G
Carbofuran G E E G G N F E G F
Permethrin G G G G G G G G G G
Lambda cyhalothrin G G G G G G G G G G
Cyfluthrin G G G G G G G G G G
Fenvalerate G G G G G G G G G G
Zeta
cypermethrin
G G G G G G G G G G
Bt N N N N N N N N N N
Azadirachtin -- -- -- -- -- -- -- -- -- --
Malathion P P P P P P P P P P
Rotation -- -- -- -- -- -- -- -- -- --
Resistant
varieties
N N N N N N N N N N
Biocontrol F F -- -- -- -- -- -- -- --
Pheromone
trap
-- -- -- -- -- P -- -- -- --

N=none, P=poor, F=fair, G=Good, E=Excellent, -- = no data.

 

Table 2. Estimated losses from commonly observed pest.

PEST*
Aphids Alfalfa
weevil
Alfalfa
caterpillar
Threecornered
alfalfa
leafhopper
Potato
leafhopper
Cutworms Army-
worms
Grass-
hopper
Blister
beetles
Estimated Damage 7% 20% 5% 8% 5% <1% 2% 2% <1%

*Loss varies from field to field and farm to farm. Other pests may be observed, however level of loss is usually less than 1%.

 

 

Insecticides

Organophosphate insecticides:

Carbamate insecticides:

Pyrethroid insecticides:

Other insecticides:

 

Table 3. Estimated Insecticide Usage*

Common name Trade name(s) % usage Ave. no apps
Methyl parathion Methyl trace 1
Chlorpyrifos Lorsban 5 1
Phosmet Imidan 0 -
Dimethoate various 0 -
Malathion various 0 -
Carbaryl Sevin 0 -
Methomyl Lannate 1 1
Carbofuran Furadan 10 1
Permethrin Ambush, Pounce 5 1
Lambda cyhalothrin Warrior 35 1
Cyfluthrin Baythroid 1 1
Zeta-cypermethrin Fury, Mustang 10 1
Bacillus thuringiensis Stewart - -
Indoxacarb Stewart - -
Azadirachtin Neemix - -

*Estimated percent acreage treated of 2004 crop.

 

 

Weeds

Various weeds occur in alfalfa production and vary from field to field and farm to farm. Johnsongrass and crabgrass are the most commonly occurring grasses. Pressure from broadleaf weeds changes mainly due crops grown or products used prior to seeding alfalfa. Weeds should be controlled during establishment of alfalfa. Competition from weeds can be one to the major factor limiting alfalfa stand establishment. Weeds such as henbit, chickweed, annual ryegrass, may pose problems in fall seeded alfalfa, while crabgrass is a major competitor in spring-seeded alfalfa. If grass is intentionally seeded with alfalfa, a grass herbicide is normally not used. Table 4, lists products recommended for use in Tennessee and the expected response of weeds to their use. Other products are available, however are rarely used. Loss due to weed infestation averages around 15% each year.

 

Table 4. Expected Weed Response to at-planting and postemergence alfalfa herbicides.

Herbicide
Weed
Eptam Butyrac Pursuit Poast or
Poast
Plus
Select Gramoxone
Between
cuttings
Annual grasses 8 0 7 9 9 7
Annual ryegrass 8* 0 -- 8* 8* NA
Johnsongrass-
Seedling
9 0 7 9 9 6
Johnsongrass-
Rhizome
6 0 6 7 9 2
Nutsedge 8 1 3 0 0 2
Chickweed 9 2 -- 0 0 NA
Cocklebur 2 8 8 0 0 6
Curly dock 0 1 -- 0 0 2
Deadnettle 8 1 -- 0 0 NA
Henbit 8 1 -- 0 0 NA
Lambsquarter 7 4 5 0 0 6
Morningglory 4 8 8 0 0 7
Pigweed 7 6 9 0 0 7
Plantain 0 2 -- 0 0 2
Ragweed 2 6 7 0 0 7
Musk thistle -- 7** -- 0 0 2

*Fall application
**Newly-emerged seedlings only
NA=not applicable
0=no control, 10=100% control; -- = data not available

 

Herbicides

The most common herbicides used include 2,4-DB, Pursuit, for broadleaf weeds and Select and Poast for grasses. Paraquat is often used between cuttings. Paraquat or glyphosate may be applied in the fall prior to seeding. A list of commonly used herbicides, classification and estimated use are listed in Table 5. Grazing and cutting restrictions for alfalfa herbicides in the presence of lactating dairy animals are listed in Table 6.

Preplant for No-tillage:

Preplant:

Seedling:

Established:

Seedling or Established Alfalfa Only:

Seedling or Established mixture:

Dormant:

Dormant established alfalfa:

Established or first year between cuttings:

 

Table 5. Herbicide classification and estimated usage.

Active Ingredient Trade name Classification Estimated
acreage
treated
Paraquat Gramoxone bipyridylium 75%
Glyphosate Touchdown, Roundup Glycine 25%
2,4-DB Butyrac 200,
Butyrac 175
Phenoxy 95%
EPTC Eptam thiocarbamate 5%
Clethodim Select, Prism cycloyhexanedione 25%
Imazethapyr Pursuit imidazolinone 38%
Sethoxydim Poast, Poast Plus cycloyhexanedione 30%
Pronamide Kerb benzamide 2%
Metribuzin Sencor, Lexone Triazinone 5%
Bromoxynil Buctril Nitrile 1%
Hexazione Velpar L Triazinone 1%
Diquat dibromide Reglone bipyridylium <1%
Norflurazone Zorial 80 pyridazinone <1%
Imazamox Raptor imidazolinone <1%

 

Table 6. Grazing and cutting restrictions for alfalfa herbicides-lactating dairy animals.

Herbicide Growth Stage Grazing Hay Cutting
Butyrac 200 Seedling 60 60
Eptam Pre 14 14
Gramoxone Max Between cuttings 30 30
Dormant 60 60
Kerb Pre 120 120
Poast or Poast Plus Established 7 14
Pursuit Established 30 30
Roundup WeatherMax Pre 56 56
Select Established 15 15
Sencor/Lexone Pre 28 28
Buctril Established 60 60
Zorial Established 28 28
Raptor Established 20 20

 

 

Diseases

Diseases can affect both the quality and yield in alfalfa. Disease problems can be separated into three major categories based on symptoms and effects: diseases that affect stand establishment and reduce persistence, those that cause root rot and stem blights, and those that cause leaf spots. Table 7, lists several diseases and estimated losses due to infection from the disease in alfalfa production.

Diseases which cause a reduction in stand and longevity include anthracnose, Fusarium wilt, Phytophthora root rot, Sclerotinia crown and stem rot, bacterial wilt, alfalfa mosaic and damping off. Alfalfa cultivars are available with resistance to anthracnose, Fusarium wilt, Phytophthora root rot and bacterial wilt. Sclerotinia crown and stem rot damage is sporadic and sometimes severe; however, a usable form of resistance has not yet been identified.

In some years southern blight can be serious, few control measures are known for stem and foliar blight diseases. However, planting cultivars adapted to the southeast and selecting sites conducive to growth will have an overall beneficial effect. The most common root rot is Phytophthora root rot and as noted above, resistant cultivars should be used to control this disease.

Leaf spots interfere with photosynthesis and cause premature defoliation. The most serious in our state are lepto leaf spot, Stemphylium leaf spot, spring leaf spot and summer leaf spot. Rust occurs during late summer and fall and can be severe if harvest is delayed. Rusts can be controlled by planting resistant cultivars, but cultivars resistant to rust as well as all four leaf spots are not available.

 

Phytophthora root rot
(Phytophthora megasperma)

Infected plants wilt, and the foliage, particularly the lower leaves, becomes yellow. Regrowth of diseased plants is often slow after cutting. Lesions with diffuse margins on the taproots are yellow to brown and usually start where a lateral root emerges. The yellow discoloration of tissue that extends through the root is a diagnostic feature of the disease. Taproots of numerous surviving plants in the field may be rotted off at various depths. If conditions do not favor the disease, new roots may form.

Chemical control:

Non-chemical pest management tools:

 

Sclerotinia crown and stem rot
(Sclerotinia trifoliorum)

Infected leaves and stems become yellow and wilted. A white fluffy mass of fungus grows over the dead plant parts or the soil surface and infecting new nearby plants. When no new tissue is available or environmental conditions are unsuitable for continued growth, the fungus produces small hard black structures called sclerotia on or in the stem and crown. Cultivars selected for adaptation in the southeast sustain less Sclerotinia crown and stem rot damage than those adapted to other regions. Sclerotinia may cause as much as 50% loss, if favorable conditions exist.

Chemical control: None.

Non-labeled possible alternative controls:

Non-chemical pest management tools:

 

Southern blight
(Sclerotium rolfsii)

The fungus produces a white cottony growth on the stem or crown near the soil surface. The plant turns tan color and dies. Small light-brown 'BB'-shaped sclerotia form on the stems and crown and on dead plant material on the ground.

Chemical control: None.

Non-Labeled possible alternative controls:

Non-chemical pest management tools:

 

Lepto leafspot
(Leptosphaerulina briosiana)

This leaf spot primarily affects young leaves, but also attacks other above ground parts. Leaf symptoms vary with the plant's age, stage of growth, and environment. Lesions often start as small black spots and either remain "pepper spots," as on white clover, or enlarge to oval to round "eyespots" 1-3 mm in diameter. The lesions have light brown to tan centers and darker brown borders - often surrounded by a white or slightly yellow ring. When conditions favoring infection and disease development coincide with rapid regrowth, lesions appear as rather large, light tan to almost white areas that merge to kill the entire leaf. High light intensity increases lesion size. Dead leaflets and petioles often remain attached to the stem for a time. In older growth, the young upper leaves become infected and have typical symptoms, but seldom die before harvesting.

Chemical control: None.

Non-chemical pest management tools: Early cutting may aid in control.

 

Stemphylium leaf spot
(Stemphylium botryosum)

Stemphylium leaf spot is caused by a fungus Stemphylium botryosum which has been often observed during cool weather in alfalfa during wet springs. The fungus produces light tan lesions that are defined by a dark border. The lesions vary in size, progressing only when there is plenty of moisture and before the border is formed. Infections reduce the quality of the hay, but are rarely severe enough to cause defoliation.

Chemical control: None.

Non-chemical pest management practices: Infected alfalfa should be cut as soon as possible to reduce spore production and spread.

 

Alfalfa mosaic virus
(alfalfa mosaic virus, AMV)

Infected plants have a light green or yellow color which may appear between the leaf veins. Plants may be stunted. Leaves may also be misshapen. This disease will normally cause plants to die after several seasons. Symptoms of alfalfa mosaic are most noticeable on new growth in the spring. However, many infected plants never show recognizable symptoms. This disease may cause greater losses and problems in other field crops such as peas, peppers and tobacco.

Chemical control: None.

Non-chemical pest management tools: Removal of infected plants

 

Anthracnose
(Colletotrichum trifolii)

Symptoms vary from a few irregularly shaped blackened spots to large, sunken, oval to diamond-shaped lesions on stems. Examination with a magnifying glass reveals tiny black hairs within these spots. Stems eventually turn straw colored and die. These dead shoots are often easily seen scattered through the field in summer and fall. This disease can move into the crown of the plant causing a bluish-black discoloration which results in damage to the whole plant.

Chemical controls: None available.

Non-chemical pest management tools: Early cutting.

Other diseases occasionally occur in alfalfa production however, damage is usually minimal.

 

Table 7. 2004 Disease loss estimate for alfalfa.

Disease Estimated Loss
Sclerotinia 4%
Phytophthoria 2%
Anthracnose 2%
Lepto leaf spot 3%
Stemphylium leaf spot 1%
Southern blight 3%
Alfalfa mosaic virus <1%

 

Fungicides

Seed Treatments: Although a number of fungicides are registered for use as seed treatments of alfalfa, clover, etc., these crops usually do not respond to seed treatments under field conditions. Some increases in stand may result but these increases have not been reflected in increased yield. The one notable exception to this is the use of fungicide seed treatment on alfalfa for control of seedling damping-off caused by Phytophthora. In areas where Phytophthora root rot has caused a serious problem in reducing alfalfa stands or preventing establishment of alfalfa, a variety with resistance to Phytophthora that has been treated with a Phytophthora specific seed treatment is highly recommended.

Fungicides available for use:

 

 

Contacts

  1. Gary Bates, Professor, University of Tennessee, Agricultural Extension Service, Plant Sciences. gbates.utk.edu, 865-974-7208. Knoxville, TN.

  2. Gene Burgess, Professor, University of Tennessee, Agricultural Extension Service, Entomology and Plant Pathology. gburgess1@utk.edu, 865-974-7959. Knoxville, TN.

  3. Darrell Hensley, Assistant Extension Specialist, Extension Service, Entomology and Plant Pathology. dhensley.utk.edu, 865-974-7958. Knoxville, TN.

  4. Melvin Newman, Professor, University of Tennessee, Agricultural Extension Service, Entomology and Plant Pathology. 731-425-4718, manewman@utk.edu. Jackson, TN. 38301.

  5. Russ Patrick, Professor, University of Tennessee, Agricultural Extension Service, Entomology and Plant Pathology. 731-425-4718, manewman@utk. Jackson, TN. 38301.

 

 

References

  1. Allen, F. L. 2003. 2003 Short List Field Crop Varieties. University of Tennessee. Agricultural Experiment Station and Agricultural Extension Service. SP 114.

  2. Burgess, G. 1997. Blister Beetles in Alfalfa Hay. University of Tennessee Agricultural Extension Service. Factsheet SP341-X.

  3. Patrick, C. R., A. Thompson, L. Steckel. 2003. Controlling the Alfalfa Weevil in Tennessee. University of Tennessee, Agricultural Extension Service. PB1033

  4. Steckel, L. and G. K. Breeden. 2003. 2003 Weed Control Manual for Tennessee. University of Tennessee, Agricultural Extension Service. PB1580.

  5. Department of Agricultural Economics: economics.ag.utk.edu/forage.html

  6. Estimating Forage Production Costs: http://economics.ag.utk.edu/budget/forage/estimate.pdf

  7. Tennessee Agricultural Statistics Service: http://www.nass.usda.gov/tn

  8. 2003 State Rankings for Crop Production: http://www.nass.usda.gov/ky/B2004/p022.pdf