E.A. Oelke1, T.M. Teynor2, P.R. Carter3, J.A. Percich1,
D.M. Noetzel1, P.R. Bloom1, R.A. Porter1, C.E.
Schertz1, J.J. Boedicker1, and E.I. Fuller1
1Departments of Agronomy and Plant Genetics, Plant Pathology, Entomology,
Soil Science, Agricultural Engineering and Agricultural and Applied Economics, Minnesota
Extension Service, and Minnesota Experiment Station, University of Minnesota, St.
Paul, MN 55108.
2Center for Alternative Plant and Animal Products, University of Minnesota,
St. Paul, MN 55108.
3Department of Agronomy, College of Agriculture and Life Sciences and
Cooperative Extension Service, University of Wisconsin - Madison, WI 53706.
Wild rice (Zizania palustris L.) is native to North America and grows predominantly
in the Great Lakes region. This large-seeded species, one of four species of wild
rice, is in the grass family (Poaceae) and has been eaten by people since
prehistoric times. Early North American inhabitants, especially the Ojibway, Menomini,
and Cree tribes in the North Central region of the continent, used the grain as
a staple food and introduced European fur traders to wild rice. Manomin, the name
they gave wild rice, means good berry. Early English explorers called this aquatic
plant wild rice or Indian rice, while the French saw a resemblance to oats and called
it folle avoine. Other names given to wild rice include Canadian rice, squaw rice,
water oats, blackbird oats, and marsh oats. However, the name "wild rice"
persisted and today it is the common name for the genus Zizania, even though
the wild type of rice (Oryza) is also called wild rice.
Prior to 1965 most wild rice in the United States was produced in natural stands
in lakes, rivers, and streams. In Canada most wild rice is still produced in lakes
and streams that are leased from the government. Growing wild rice as a field crop
was first suggested in 1852 by Joseph Bowron from Wisconsin, and in 1853 by Oliver
H. Kelley of Minnesota. Efforts to grow wild rice as a field crop did not begin
until 1950. James and Gerald Godward grew wild rice in a one-acre diked, flooded
field (paddy) near Merrifield, Minnesota. By 1958 they had 120 acres of paddies
for growing wild rice. Additional growers started paddy production during the mid-1950s
and early 1960s, and in 1965, Uncle Ben, Inc. started contracting acreages. These
initial efforts to commercialize wild rice production resulted in an organized effort
to domesticate this crop using plant breeding.
Development of more shatter-resistant varieties was largely responsible for the
rapid expansion of field production in the late 1960s and early 1970s. Production
in Minnesota increased from 900 acres in 1968 to 18,000 acres in 1973. Most wild
rice from natural stands was harvested by hand prior to this time using the traditional
canoe-and-flail method. Mechanical harvesting of wild rice on private
lands began during 1917 in Canada. Harvesting with more efficient grain combines
was possible with the discovery of shattering resistance. Wild rice is currently
produced commercially as a field crop in Minnesota and California, which account
for most of the acreage (20,000 and 8,000 acres, respectively, in 1991). Additional
amounts are grown as a field crop in Idaho, Wisconsin and Oregon. In Canada, there
has been much recent effort to increase total production from lakes by seeding lakes
that were without wild rice. The lakes are then mechanically harvested by airboats
equipped with collecting troughs. Researchers in Europe are currently investigating
the possibility of wild rice production there.
Wild rice is a nutritional grain that serves as a substitute for potatoes or rice,
and is used in a wide variety of foods such as dressings, casseroles, soups, salads,
and desserts. In recent years, wild rice has been used in breakfast cereals, and
mixes for pancakes, muffins, and cookies. Blends of wild rice and long-grain regular
rice (Oryza) that were introduced in the early 1960s increased the popularity
of wild rice among consumers. Wild rice from natural stands is popular among health-food
This grain has a high protein and carbohydrate content, and is very low in fat (Table
1). The nutritional quality of wild rice appears to equal or surpass that of other
cereals. Lysine and methionine comprise a higher percentage of the amino acids in
the protein than in most other cereals. The SLTM value (sum of lysine, threonine,
and methionine contents) often serve as a measure of the nutritional quality of
cereals, and is a little higher for wild rice than for oat groats, which is one
of the better cereals for humans. Amino acid composition of processed and unprocessed
wild rice is similar, which indicates little reduction in nutritional quality during
processing. Wild rice contains less than one percent fat, of which linolenic and
linoleic acids together comprise a larger proportion of the fatty acids (68%) than
in wheat, rice, or oats. Although these two fatty acids are easily oxidized and
make wild rice prone to develop rancid odors, the high levels of linolenic acid
make the fat in wild rice highly nutritious.
Mineral content of wild rice, which is high in potassium and phosphorus, compares
favorably with wheat (Table 1), oats, and corn. Processed wild rice contains no
vitamin A, but serves as an excellent source of the B vitamins: thiamine, riboflavin,
Table 1. Nutritional composition of wild rice, cultivated brown rice, and wheat.
Cultivated Brown Rice
Ether Extract (%)
Nitrogen (free % extract)
aNumbers in parentheses indicate ranges in values. Source: Handbook of
Cereal Science and Technology, Chp. 10, Oelke and Boedicker, 1991; and Wild Rice:
Nutritional Review, R.A. Anderson, 1976.
III. Growth Habit:
Wild rice is an annual, cross-pollinated species. In Minnesota, it matures in about
110 days, and requires about 2,600 growing degree days (40o F base).
Plants are five to six ft tall and can have up to 50 tillers per plant. In cultivated
fields that have four plants/sq ft, plants usually have three to six tillers. Stems
are hollow except at nodes where leaves, tillers, roots, and flowers appear. Internodes
are separated by thin parchment-like partitions. The shallow root system has a spread
of 8 to 12 in. Mature roots are straight and spongy. Ribbon-like leaf blades vary
in width from 1/2 to 1 1/2 in. Mature plants have five or six leaves per stem or
tiller above the water.
Flowers are in a branching panicle with female (pistillate) flowers at the top and
male (staminate) flowers on the lower portion. Cross pollination usually occurs
since female flowers emerge first and become receptive and are pollinated before
male flowers shed pollen on the same panicle. Sometimes the transition florets,
which are located between the pistillate and staminate florets on the panicle, have
both stigmas and anthers (pollen), and can therefore be self-pollinated. Two weeks
after fertilization the wild rice seeds are visible, and after four weeks, it is
ready for harvest. This seed is a caryopsis that is similar to the grain of cereals.
The caryopsis has an impermeable pericarp, large endosperm, and small embryo. The
grains with the palea and lemma (hulls) removed, range from 0.3 to 0.6 in. in length,
and from 0.06 to 0.18 in. in diameter. Immature seeds are green, but turn a purple-black
color as they reach maturity. Seeds on any tiller will mature at different times,
and on secondary tillers they mature later than on main tillers. There is little
shattering resistance in natural stands.
Seeds will not germinate for at least three months after reaching maturity, even
if environmental conditions are satisfactory for growth. An after-ripening period
is required in water at freezing or near-freezing temperatures (35o F)
before the embryo breaks dormancy and develops into a new seedling. This seed dormancy
is caused by the impermeable pericarp that is covered by a layer of wax, and by
an imbalance of endogenous chemical growth promotors and inhibitors. In the spring,
seeds will start to germinate when the water temperature reaches about 45o
F. Freshly harvested seeds can be made to germinate by carefully scraping off the
pericarp directly above the embryo. These seeds cannot be planted directly, but
must first be germinated in water, and then the seedlings transplanted later.
IV. Environmental Requirements:
Wild rice is well adapted to northern latitudes. It is not very productive in the
southern United States since warm temperatures accelerate plant growth, and as a
result, plant heights are shorter with an accompanying lower number of florets.
The number of florets per panicle also decreases when the daylength is shorter than
14 hours. However, moderate yields have been produced in southern climates when
planted in late February or early March. Northern California, Idaho and Oregon have
recently been other areas where wild rice has produced good yields.
Wild rice in Minnesota and Wisconsin is usually produced on low, wet land that has
never or seldom been farmed. The paddy site should be flat enough to avoid expensive
or excessive grading that would expose the subsoil. This crop grows well on shallow
peat soils, and clay or sandy loams. The site should have an impervious subsoil,
such as clay, which prevents seepage during most of the growing season and is a
solid footing for heavy field equipment. The majority of wild rice fields have been
developed on organic soils with a peat depth ranging from several inches to more
than 5 ft. Peat areas in Minnesota, except for acid bogs which are low in fertility,
are ideal for growing wild rice since they are generally flat and slightly above
the flood plain. Peats with pH < 5.5 as well as sphagnum bogs should be avoided.
Ideally, the soil should contain > 20% mineral matter and have a carbon to nitrogen
ratio less than 16.
C. Land Preparation and Dike Construction:
Brush and small trees on a new paddy site are usually removed during winter by shearing
with a bulldozer, and then burned the following summer, if weather conditions permit.
Large disks or rotovators are used to till the soil rather than moldboard plows.
When sod peats are turned over with a moldboard plow the rotting vegetation can
produce enough carbon dioxide and methane to cause the soil to float when flooded.
A detailed topographic survey is needed to help determine the dike height, location
of culverts, and portions of the paddy that should be levelled.
Small fields will have a perimeter dike and water outlet at the lower side. Fields
that are 30 or more acres in size will have cross dikes with water gates, as well
as the larger perimeter dike. A slight slope of less than one-half percent (six
in. per 100 ft) within the paddy promotes preharvest drainage. Tiling of larger
fields is common now to promote drainage and fall tillage.
Dikes must be impervious to water. Clay soil is ideal for dike construction. The
dikes must be wider if peat soil is used. The top width of the main dike should
be eight ft, while the inner dike should have a minimum top width of four ft, but
never less than the height of the dike. The steepest side slopes should be 1.5:1
(1.5 ft of horizontal distance for every one ft drop) and the height should be one-half
to one ft above the water level. On highly erodible soils, the slope should be 3:1,
and the height of the dike should be one to two ft higher than the water level.
Use of organic soil for dikes may cause problems since peat erodes easily and may
not hold back water. The sides of the dike may need to be flatter than the minimum
recommended height to provide wave protection and fill stability. A mixture of mineral
soil with peat soil may reduce erosion problems, especially on the sides of dikes.
Place dikes so that a maximum water depth of 8 in. can be maintained in the shallow
end and 16 in. in the deep end of the field.
Access roads should be located so they can serve as part of the dike system to divert
or collect water and to divide the drainage areas. Culverts or other permanent structures
should be positioned where roads cross the drainage channels to provide access to
every field for easy observation and movement of equipment. The location and size
of culverts, water gates, and pumps should be determined prior to construction so
the desired water control can be achieved.
Wild rice in natural stands grows in water with a concentration of less than 10
parts per million (ppm) of sulfate. Research has found that wild rice can grow satisfactorily
in water with sulfate concentrations of up to 250 ppm. The growth of wild rice is
also tolerant to a wide variation in the hardness (22 to 300 ppm calcium carbonate)
and pH (5.0 to 8.0) of the water.
This crop will thrive only in flooded soils. Flood the fields as early as possible
in the spring. If seeds germinate in unflooded soils, the seedlings are stunted
and yellow in color probably due to lack of iron. Soils should be saturated from
germination until 2 or 3 weeks before harvest to ensure vigorous plant growth. A
constant water depth of at least 6 in. is important to help control weeds during
the first 8 to 10 weeks after seeds germinate. Variable water depths during this
period can damage wild rice plants. Water deeper than 14 in. causes weak stems and
lodging during water drawdown. A 3-year study conducted in northern Minnesota indicated
that a 13-in. water depth resulted in adequate plant populations, no delay in maturity,
good yields, and the best weed control during the early portion of the season. To
maintain the proper depth, water should be added as needed to compensate for soil
percolation, evaporation, and plant transpiration. The water level can be permitted
to decrease slowly during flowering so that little water needs to be drained 2 or
3 weeks prior to harvest.
An acceptable water source must be available from a stream or lake. Permits are
required in Minnesota from the Department of Natural Resources to use surface or
ground water for irrigation, and from the Pollution Control Agency for the drainage
of water from paddies. These permits are available only to landowners whose fields
are next to the water source. Wells can also be used if the recharge rate is sufficient.
Applications for these permits should begin early in the planning stage to assure
they are granted prior to construction.
One possible plan for an irrigation system has a central water supply ditch from
which numerous fields can be flooded. A second system allows water to flow from
one field to another. However, this system does not allow crop rotation or fallowing
of individual fields. The amount of water needed to grow this crop varies from 24
to 30 acre-in. Research conducted by the University of Minnesota found that wild
rice with a plant density of two plants/sq ft required 25 acre-in. during the growing
season. Most growers have water-use permits that allow them to pump this amount
of water, but nearly half is often supplied by rainfall. The water system should
flood a field in 7 to 10 days. A 30-acre field requires about 15 million gallons
of water for the initial flooding. A 12-in. pump that delivers 4,000 gallons per
minute, and operates for 24 hours a day, will deliver 5,760,000 gallons per day.
This pump would take 2 1/2 days to flood a 30-acre paddy to a depth of 11 in. Less
water would need to be pumped in subsequent years when the winter snow and spring
rains are retained after the water gates of paddies are closed following the harvest
in the fall.
E. Seed Preparation and Germination:
Plant new fields with the most shatter-resistant varieties. New producers should
make arrangements to buy seed from seed growers before harvest in the fall. Some
certified seed of new varieties is available. Growers can save their own seed, but
it should be from weed-free fields. Seed should be cleaned immediately after harvest
with an air or gravity cleaner before fall planting or winter storage that precedes
spring planting. If the seed will be stored, even if for a short time, it must be
placed in water to assure germination. Seed used for fall planting is usually placed
in tanks filled with water. Seed for spring planting can be stored in 50-gallon
drums that are perforated with many small holes or plastic-mesh bags to permit water
circulation. The drums or bags are placed below the ice in lakes or streams, or
in water-filled pits that are 10 ft deep. Do not let mud cover the seed or allow
water surrounding the seed to freeze. Seed can also be stored in tanks where the
water is kept at 33 to 35o F and it should be changed every three to
Seed dormancy will prevent germination until after three months of cold (33 to 35o
F) storage in water. The percent germination is determined by placing seeds in a
pan of water at room temperature (68o F). The water should be changed
every two days, and after 21 days, high quality seed should have a 70% or higher
germination rate. Seed germinates at 42o F, but the optimum temperature
is between 64 to 70o F. Viability of dormant seed can be checked by removing
the pericarp above the embryo and then placing the seed in a pan of water, or by
performing the tetrazolium test.
V. Cultural Practices:
A. Seedbed Preparation:
A new wild rice field that has a large amount of vegetation should be tilled one
or more years before planting. Small grains such as oats or winter rye can also
be grown for one or two years prior to planting wild rice. This initial cropping,
prior to flooding the fields, allows vegetation to decompose and reduces problems
with floating peat when fields are flooded. Frequently, a rotovator is used to till
the soil to a six-in. depth. A roller or row of tires is often attached to the rear
of the rotovator for better floatation on peat soils. A disk can be used to prepare
the seedbed, but it is not as effective as a rotovator in destroying and incorporating
the existing vegetation. Moldboard plows are not satisfactory for primary tillage
of peat soils with vegetation since the turned-over soil may float when the field
is flooded. Land-breaking plows will cause less soil flotation, but should not be
used in shallow peat where the underlying mineral soil is brought to the surface.
Wild rice is difficult to establish on clay subsoil. The final seedbed should be
free of ridges and depressions to ensure good water drainage.
Fall tillage is recommended for seedbed preparation, weed control, fertilizer incorporation,
and covering plant residue to decrease the severity of leaf diseases in the following
year. Growers often fallow fields during the third year. Soil is removed from ditches
in the perimeter of fallow fields to maintain good drainage and ease of tillage
and harvesting. Other crops can be grown in rotation with wild rice, such as buckwheat,
rye, wheat, mustard, canola, or forage grasses for seed production. Barley should
not be in the rotation because it is an alternate host of brown spot which is a
severe disease in wild rice.
Changing a field to a new variety is not easy since wild rice seeds survive in the
soil for several years. The eradication of seeds from the old variety begins by
not doing the fall tillage. Seeds that remain on the soil surface during the winter
will die. The field should be flooded in the spring to permit germination, and after
four to six weeks, the field should be drained and tilled to eliminate any plants.
A short-season crop like buckwheat could be planted following the summer tillage.
After two years this system should eliminate most of the seed from the old variety.
Another method for changing varieties has been successful in areas with a peat layer
that is more than 24 in. thick. The field is plowed 20 to 24 in. deep in the fall
to bury the seed so seedlings are unable to emerge. This system has allowed some
growers to change a field to a new variety in one year.
B. Seeding Date:
Wild rice can be seeded in the fall or spring. Fall planting is preferred since
it is the natural seeding time, and eliminates the need to store seed over winter.
Other advantages of fall seeding are that the weather is mild, and fields are usually
dry so heavy field equipment can be used. However, if the soil is too dry, the fields
may need to be flooded immediately after planting to prevent the seeds from drying
out. Spring seeding should occur as early as possible before the seeds begin to
sprout. A seeding trial at Grand Rapids, Minnesota found that planting the variety
K2 after June 1 was too late in the growing season to allow the crop to mature.
C. Method and Rate of Seeding:
Do not allow the wild rice seed to dry during planting. Drain the water from the
seed just before planting and then mix it with oats in a ratio of 2 or 3 lb of oats
per lb of wild rice. This combination allows the wild rice seed to flow uniformly
through the seeding equipment. Successful planting requires that the seed is covered
promptly with soil or water to maintain viability and minimize feeding losses from
Wild rice should be planted at a depth of one to three in. Seedlings will not emerge
when planted deeper than 3 in. Mineral soils require a shallower planting depth
than peat soils. Wild rice may be planted by using a bulk-fertilizer spreader to
broadcast the seed, which is followed by using a disk or harrow to incorporate it
to a depth of 1 to 2 in. A grain drill may also be used. These seeding methods cannot
be used in the spring due to wet field conditions. Seed is usually sown directly
into the water from an airplane or broadcasting equipment in the spring. Seeding
rates that are 15 to 20% higher should be used when planting directly into water.
A plant density of 4 plants/sq ft is recommended. Higher plant populations have
lodging and leaf-disease problems. Planting rate with good quality seed should be
30 to 45 lb/acre. The amount of seed needed to obtain the optimum plant density
varies with the seed quality, which is reflected by the germination rate. Germination
rates of commercial seed can vary from 15 to 95%.
In second-year and older fields, varieties will reseed themselves. A very high plant
population will result since up to 1,000 lbs of seed per acre can shatter before
harvest. Reducing the plant population is necessary to produce higher yields. Plants
are thinned at the floating-leaf stage. The thinning is done by an airboat with
a series of V-shaped knives set six to eight in. apart on a toolbar attached to
the rear of the boat. The boat travels at a speed of 35 m.p.h. with the knives riding
on the soil surface, and removes approximately 70% of the plants. The plant density
should then be 4 plants/sq ft. Sometimes it is necessary to thin fields with a second
series of passes that are perpendicular to the first series.
D. Fertility and Lime Requirements:
Flooding a field to grow wild rice causes changes in several chemical systems of
the soil that affect plant nutrition. The only form of nitrogen that is stable in
flooded soils is ammonium. Nitrate nitrogen is rapidly lost due to the formation
of dinitrogen gas. Consequently, only ammonium based fertilizers, including urea,
should be used on wild rice. Also, fall testing for nitrate nitrogen, as is done
in small grains, is not useful in making fertilizer recommendations in wild rice.
Ammonium nitrogen near the surface of a flooded soil can be oxidized to nitrate
then lost by being transformed to dinitrogen gas. To minimize this type of loss
nitrogen should be plowed under with a moldboard plow or injected to a depth of
6 to 8 in.
Phosphorus and potassium are both more highly available in peat soils than in mineral
soils and tend to be more highly available in flooded mineral soils than nonflooded
mineral soils. Leaching losses are possible but in well managed wild rice paddies
leaching is not much of a problem. Phosphorus in the flood water enhances algae
growth which can be a problem especially in the early stages of wild rice growth.
Phosphorus fertilizers should be injected or plowed in.
The availability of iron and manganese increase greatly upon flooding. Wild rice
does not have the ability to obtain sufficient iron in nonflooded soils and iron
availability is one of the major reasons wild rice must be grown in flooded soils.
The wild rice plant has a relatively high requirement for plant nutrients for each
pound of dry matter produced. This crop grows rather slowly during the vegetative
phase, so that by jointing, less than 12% of total dry weight is produced. Most
plant growth and dry matter accumulation occurs during flowering and grain maturation.
Consequently, the nitrogen requirement for wild rice is greatest during the reproductive
phase when 70% of the total nitrogen is assimilated by the plant. Growers often
apply 30 to 50 lb/acre of urea nitrogen by air at the late boot stage to supply
sufficient nitrogen for grain fill. Assimilation of phosphorus and potassium follow
a similar pattern during crop development.
Plants that are nitrogen-deficient are shorter and have a lighter green color than
plants with a sufficient amount. Lower leaves of nitrogen-deficient plants have
yellow tips and margins. A slight deficiency of nitrogen results in less lodging,
vegetative growth, and damage from brown spot disease. In addition, yields are higher
and harvesting with a combine is easier. Sulfur deficiency can also result in a
yellowing that looks similar to nitrogen deficiency. Experiments with sulfur application
have not yielded consistent results but the data are suggestive of a response to
fertilization for some acid peats with pH less than 6.
Soil testing and plant analysis are the best methods to determine how much fertilizer
may be needed by a wild rice crop. The amounts of nitrogen, phosphate, and potassium
fertilizer that are recommended for wild rice by the University of Minnesota Soil
Testing Laboratory are summarized in Table 2. Tissue nitrogen concentrations of
less than 3.5% in the boot stage suggest that fly-on nitrogen, in addition to that
normally applied, is needed. Liming has not been effective and liming of acid peats
can result in gas production and floating of the soil. If lime is applied the soil
should be fallowed or used for an upland crop for one more season. Fertilization
with sulfur may be helpful in some acid peats but there is no documented evidence
of response to other micronutrients.
Table 2. Fertilizer recommendations for wild rice1 .
Amount to Apply (lb/acre)
Status of Paddy:
First year only
Second year and older
Soil Test Results (ppm)
Amount to Apply (lb/acre)
1Source: Fertilizer Recommendations for Agronomic Crops in Minnesota.
1990. George Rehm and Michael Schmitt, University of Minnesota, Minnesota Extension
Service, AG-MI-3901, 1990.
Much of the nitrogen can be applied in the fall if it is incorporated to a depth
of 6 to 8 in. All ammonium sources, anhydrous ammonia, aqua ammonia, ammonium phosphate,
and urea, work equally well. Urea ammonium nitrate, UAN, has 29% of the nitrogen
in the nitrate form which will be lost to the atmosphere. This source can be used
for wild rice but only 71% of the nitrogen that is applied will be available for
wild rice. The phosphorus fertilizer should also be incorporated into the soil to
help control algae. Application of phosphorus in the spring should be avoided. If
conditions do not permit fall application of fertilizer it is better not to apply
phosphorus in the spring. In fields that have been cropped for several years, the
buildup of phosphorus from previous fertilization will probably supply the crop
with sufficient P.
Under some conditions, losses of fall applied nitrogen can be high. In drained soils
ammonium is converted by soil microbes into nitrate which will be lost after flooding
in the spring. The rate of the process is slower at lower temperatures and fall
fertilization is not recommended until the temperature at 6 to 8 in. depth is lessF.
Even at this temperature much of the ammonium can be converted to nitrate within
2 to 3 weeks if the soil is well drained. Fall flooding, within 5 days after nitrogen
application, will stop nitrification and result in a better efficiency for fall
nitrogen fertilization. Topdress applications of urea should be made at the boot
stage or very early flowering.
E. Variety Selection:
Most of the paddy-grown wild rice in Minnesota and Wisconsin is produced using varieties
that have a nonshattering tendency. All the following varieties shatter somewhat
and are susceptible to lodging and diseases. The most popular variety is K2.
K2- has a medium height, early to medium maturity, and medium to high yield. Developed
by Kosbau Brothers in 1972. by Kosbau Brothers in 1972.
M3- has a medium height, medium to late maturity, high yield, and variable plant
and panicle type. Developed by Manomin Development Co. in 1974.
Meter- has a shorter height, very early maturity, low to medium yield, and large
seed size. Reduced foliage in the canopy compared to other varieties. Released by
the Minnesota Agricultural Experiment Station in 1985.
Netum- has a medium height, early maturity, and low to medium yield. Released by
the Minnesota Agricultural Experiment Station in 1978.
Voyager- has a short to medium height, early maturity, and medium to high yield.
Should equal or exceed K2 in yield and mature a few days earlier. Released by the
Minnesota Agricultural Experiment Station in 1Yield and other agronomic characteristics
are shown in Table 3.
Table 3. Yield and other characteristics of wild rice varieties evaluated in Minnesota.
------- lb/acre2 -------
---- %3 ----
1Data for 1990 was from Grand Rapids, Minnesota, and for 1989 it was
from on-farm site and Grand Rapids combined.
2Green weight of harvested grain adjusted to a 40% moisture content.
3Shattering expressed as percent of total possible yield (sum of the
harvested and shattered grain).
4Number of seeds per pound based on wet, stored seed. Seed size will
vary among years and seed lots. Source: 1991 Varietal Trials of Selected Farm Crops,
Minnesota Agricultural Experiment Station, Minnesota Report 221-1991.
Certified seed is not available of the above varieties except during the first year
of release. Growers maintain and sometimes select their own seed and new growers
need to make arrangements for seed with current growers during harvest. Because
of cross-pollination variety integrity is difficult to maintain in a field, thus
most seed is not the same as the original variety unless reselection has been done.
The breeding program at the University of Minnesota is continuing to develop varieties
for future release.
F. Weed Control:
The common broadleaf water weeds of the Upper Midwest are a more serious problem
than aquatic grassy weeds. Common waterplantain (Alisma plantago- aquaticai>Alisma
plantago- aquatica L.) an aquatic perennial weed, is the most troublesome
weed in wild rice fields. Research conducted by the University of Minnesota found
that waterplantain which developed from corms caused yield losses of 43% when one
weed/sq ft was present. Early control of waterplantain is critical since competition
with wild rice is greatest after 8 weeks of growth. First-year seedlings of waterplantain
are usually too small and late in appearance to compete with wild rice. Weed seedlings
should be controlled since they will cause problems in succeeding years. Consult
the Minnesota Extension bulletin on wild rice production for a discussion of other
weeds that are present in paddies, yet are usually not economically significant.
Control of weeds should consist of a combination of cultural and chemical methods.
Fall tillage after harvest will control cattails (Typha latifolia L.) and
reduce plant numbers of common waterplantain. Other effective methods to control
aquatic weeds include the use of weed-free seed, maintenance of the water depth
at six to ten in. especially during the first 6 weeks, and to fallow weedy fields
for a year. The fallow fields should be flooded in the spring for 6 weeks to ensure
the growth of weeds, and then drained, so they can be tilled to destroy wePresently,
the only herbicide that can be used in Minnesota for controlling weeds in wild rice
is 2,4-D (amine) at one-quarter pound of active ingredient per acre. No herbicides
are cleared for use in Wisconsin. 2,4-D should be applied when wild rice is in the
tillering stage since considerable injury can occur with later applications. Avoid
spray overlaps in the field because one-half pound of active ingredient per acre
can injure the crop. This herbicide does not give complete control of waterplantain,
but will reduce the infestation in the following year. Algae can form a mat on the
water surface before wild rice emerges, which will reduce the stand in some areas
of the field. Copper sulfate applied at 15 lb/acre into the flood water may help
to control algae. Retreatment is often necessary for complete control. Consult your
Extension agent or specialist for current herbicide recommendations.
G. Diseases and Control:
Diseases in natural stands of wild rice are not usually destructive, but in field-grown
wild rice they can cause serious losses. In the early years of commercial production,
severe epidemics of brown spot destroyed entire crops in some locations. Almost
every disease pathogen of wild rice has been observed previously on rice previously
on rice (Oryza).
Brown spot (formerly called Helminthosporium brown spot) is the most serious
disease affecting wild rice that is grown in fields. This disease is caused by Bipolaris
oryzae Luttrell (Helminthosporium oryzae B. de Haan) and B. sorokiniana
Luttrell (H. sativum P.K. and B.). These fungi are considered to cause brown
spot since both are found on infected plants and cause similar symptoms in wild
rice plants. Every variety of wild rice, at each stage of development, is susceptible
to brown spot. This disease is most severe when day temperatures range from 77 to
95o F and nights are 68o F or warmer. High relative humidity
(greater than 89%), and the continuous presence of free water on leaf surfaces for
11 to 16 hours, can also favor infection. All parts of the plant are susceptible
to infection. The brown, oval leaf spots usually have yellow margins and are about
the size of sesame seeds. These spots are uniform and evenly distributed over the
leaf surface. Severe infections cause weakened and broken stems, damaged florets,
and a reduced quantity and quality of grain. Yield reductions can vary from insignificant
Sanitation and appropriate cultural methods are important parts of a program to
control disease. Disease problems are reduced by the incorporation of crop residue
into the soil after harvest, planting disease-free seed in new fields, using rotation
crops resistant to brown spot or fallowing fields, and planting grass or other plants
on dikes that are not alternate hosts. Barley and reed canarygrass are alternate
hosts. Application of a balanced fertilizer can also reduce the severity of disease
problems by avoiding nutrient deficiencies which can predispose plants. Higher plant
densities than 4 plants/sq ft can also lead to more disease. Use of propiconazole
(Tilt), a fungicide, may be necessary. Apply 6 oz/acre at the boot stage followed
by an additional 6 oz 14 to 17 days later at early flowering. This fungicide is
approved for use on wild rice in Minnesota.
Stem rot is the second most common disease in field-grown wild rice. Two fungi,
a Sclerotium sp. and Helminthosporium sigmoidium Cav., may cause this
disease. These fungi produce dark structures called sclerotia in culms, leaf sheaths,
and stems. Sclerotia survive in infected plant debris or float in the water until
deposited on the soil surface when paddies are drained. In the spring, sclerotia
germinate and produce conidia (infective spores) that are spread by the wind or
by sclerotia themselves, which can float to new plants and infect at the water level.
Small, oval, purple lesions develop initially on stems or leaves at the water surface.
Extensive lodging may result after the fields are drained prior to harvest, since
the infected stems become necrotic, dry, and brittle. Control of stem rot is achieved
most effectively by appropriate sanitation and cultural practices such as burning
the residue. Plant residue must be removed or tilled into the soil, only clean seed
should be used, and resistant crops or fallow should be in the rotation. There is
no fungicide available for effective control.
Stem smut is caused by the fungus Entyloma lineatum (Cke.) Davis. Economic
losses from this disease have not been a problem in cultivated fields.
Ergot is rarely found in cultivated fields of Minnesota, but can be a serious problem
in natural stands. This disease is caused by the fungus Claviceps zizaniae
Fyles, which is a different species than the one causing ergot in cereal grains.
Wind-borne ascospores infect flowers and hard, dark sclerotia eventually develop
in place of the grain. No specific control is recommended, but poisonous ergot bodies
should be removed from harvested grain by flotation, or by screening.
Bacterial leaf streak caused by (Pseudomonas syringae pv. zizaniae)
and Xanthomonas oryzae, as well as bacterial leaf spot (P. syringae
pv. syringae) have been found in cultivated wild rice in Minnesota. The wheat
streak mosaic virus-wild rice (WSMV-WR) is the only one known to infect wild rice.
The eriophyid mite ve Keif., which is commonly found on wild rice, retains WSMV-WR
for several days and can be transported long distances by wind. Economic losses
for grain yield, if any by these diseases, have not been determined. No control
measures are known.
H. Insects and Other Pests:
The rice worm (Apamea apamiformis Guenee), which is the larval stage of the
noctuid moth, is the most serious insect pest of wild rice in the Upper Midwest.
Significant yield losses have been caused by this insect. Its life cycle is coordinated
closely with the growth and development of wild rice. Adult moths begin to emerge
at about the same time as flowering begins in wild rice during late June or early
July. Nectar from milkweed flowers serves as the primary food source for adult moths
through August. Eggs are deposited in wild rice flowers over a period of 4 to 6
weeks. Larvae hatch and develop through several instars or stages, and feed as they
grow. Yield potential is reduced by the initial feeding activity on the glumes of
the spikelet and subsequent feeding on kernels. Rice worms bore into stems of wild
rice or migrate to plants that border the production area as their growth and development
nears completion. Rice worms overwinter inside the stems in the seventh instar.
After a final molt and some additional feeding in the spring, the larvae usually
pupate in early June, and develop into the adult moth. Research in Minnesota found
that one larva per plant reduces yield by 10%. Control of the rice worm has been
effective with several insecticides; yet only malathion at one pound of active ingredient
per acre is approved for use in Minnesota. Malathion should be applied 14 to 21
days after eggs become visible in the bracts at the base of florets. Control is
only economical if there are 10 or more larvae per 100 panicles.
A number of midges use the flooded paddies for larval development. Eggs are laid
in the moist soil and hatch when the fields are flooded. One of the midges, Cricotopus
spp., has caused severe damage to first-year fields. The mosquito-like adults
are so small that most growers will not see them. Algal growth is associated with
paddies showing high midge numbers. A slow emergence of seedlings results in greater
damage by midges since it allows more time for feeding activity. The larvae feed
on leaf edges and cause frayed leaf edges with subsequent curling of leaves. The
leaf curling and webbing that midges produce will interfere with seedling emergence
above the water. As a result, the damaged seedlings fail to reach the floating-leaf
stage and the stand is thinned severely. Midge control with malathion is often necessary
in first-year fields. In the following years control is not usually necessary since
there is no economic loss. This is not the result of a lack of midges, which actually
increase in number, but due to higher plant numbers so the damage goes unnoticed.
Rice stalk borers (Chilo plejadellus Zincken), rice water weevils (Lissorhoptrus
spp.), rice leafminer (Hydrellia spp.), rice stem maggot (Eribolus longulus
Loew), and other insects will feed on wild rice plants. Research in Minnesota did
not reveal any economic injury from these insects.
Crayfish (Orconectes virilis Hagen) are carried into paddies by flood waters
where they forage and may cut back the seedlings. Once crayfish are established
in a field, they persist and can increase in number. They survive in production
fields by burrowing into moist soil between periods of paddy flooding. Severe stand
reductions have occurred in some fields in Minnesota. No chemicals are cleared for
Blackbirds are a major pest. These birds use the paddy dikes as nesting sites and
are present in large numbers in the growing areas. Birds begin feeding on wild rice
when the kernels are in the milk stage. Control measures should start when blackbirds
are first observed in the area. Numerous methods of bird management have been used
by commercial growers. Shooting, carbon-dioxide guns or bangers, Av-Alarm records,
and continuous overflights by aircraft have been tried or are now used by producers.
Oats have been planted around the perimeter of fields to draw the birds away from
the wild rice. Methiocarb (Mesurol) has been investigated as a chemical bird repellent,
since it causes illness and conditions an aversion to wild rice. This repellent
must be applied uniformly on hulls of wild rice grains to be effective. It is difficult
to apply methiocarb uniformly to the grain under field conditions, which results
in an inconsistent effectiveness in repelling birds. However, methiocarb has not
yet been approved for this use. There is no method that has been completely effective
in keeping blackbirds away from production fields.
Wild rice fields are also ideal sites for resting, foraging, nesting, and raising
broods of migratory and resident water birds. Four species of ducks (mallard, pintail,
blue-wing teal, and green-wing teal) and more than 35 species of shorebirds and
wading birds inhabit wild rice paddies. Economic damage from waterfowl is rarely
observed. Paddies are excellent areas for duck productRaccoon, mink, and skunk search
for food on the dikes and in ditches. Deer and moose occasionally cause some damage
in the fields, but it usually has no economic importance. Muskrats can cause problems
by feeding on plants and by burrowing holes in the sides of dikes. However, since
muskrats are not permanent inhabitants due to the annual drainage of the paddies
for the harvest, they do not pose a threat to the dikes.
Paddies should be drained gradually in late July and early August during grain fill.
It usually takes about two to three weeks for paddies to drain and become dry, but
will vary with soil type and if drain tiles have been installed. Drainage allows
the soil to dry so it can support harvest machinery. Peat soils must be drained
completely, although harvesting is possible on mineral soils with some standing
Maximum yields of processed wild rice are obtained when about one-third of the grain
at harvest time is greenish brown or black, rather than green in color. The grain
at this time has the consistency of firm dough and contains 35 to 40% moisture.
This moisture content usually occurs when some of the seeds have fallen from the
main stem, but very few have dropped from tillers on the same plant. Growers may
not always be able to wait until this time to harvest due to imminent climatic conditions
such as frost, high winds, and hail. Some paddies may need to be harvested early
if enough combines are not available to do all the fields in a short time. The harvest
of nonshattering varieties usually begins in early to mid-August.ins in early to
Direct harvest with a combine is possible since shatter resistance and uniformity
of maturation have been improved compared to the original lake types. Field conditions
result in severe limitations of machinery that are not found usually in the harvest
of other crops. High capacity combines are required to harvest wild rice because
the plants are still green. Ground conditions are extremely wet even though fields
are drained 2 to 3 weeks before harvest. The crop stubble provides little support
for combines since wild rice is a poor sod former and the organic soils on which
this crop is usually grown lose most of the fiber strength from tillage.
Growers have made innovative changes to various components of combines such as reels,
grain divide points, draper systems, and track-type support systems. Reels seven
feet or more in diameter are needed to allow the reel bats to enter the crop without
pushing it forward. Extended bats on the reel and crop-divide points prevent the
straw from wrapping around rotating parts of the combine. The pickup-type reel is
considered necessary to reduce shattering since the bats remain parallel to the
original position as they rotate. Reel tines should be adjusted to point downward
or somewhat rearward to provide lifting action. This adjustment, which gives a positive
pitch to the pick-up teeth, also prevents a pressing action on the crop.
A header equipped with a draper extension between the sickle and crossauger is used
due to the height of wild rice plants. This extension provides a space in which
plants fall before entering the crossauger and a "live" surface to assist
in moving plant material to the cross-auger. The divide point of combine grain header
is usually modified to handle this crop. Larger and different divide points are
used to avoid the hairpining of stems and accumulation of straw on the end of the
header. Spike-tooth cylinders are effective for threshing heavy clumps of crop material.
Rasp-bar cylinders effectively separate a large portion of the grain through the
concave rather than passing it to the walkers. Rasp-bar cylinders leave straw in
larger pieces, which results in easier separation of straw and grain on the walkers
The very soft soil of paddies requires an effective support system. Extensive support
systems for combines range from conventional half-tracks with dual guide wheels
to full-track systems with 45-in. pads bolted to each track shoe. Half-track systems
are standard attachments for most combines. The addition of planking to reduce ground
support pressure is fairly quick and easy to accomplish. This modification places
the ground support pressure of paddy soils in the range of an individual's foot.
A full-track system must be used in more difficult situations. Conversion to a full-track
system is a major project that is usually done by the grower. Guide wheels are removed
and the rear of the combine is mounted on a "walking beam" that is supported
on the channel frames of the two tracks. The original steering and brake systems
must also be changed since there are no guide wheels. A steering clutch is installed
in the right and left drive shafts so the original steering and brake systems can
continue to control these operations. The steering clutches require widening the
track tread, but allow the use of wider pads on the tracks. Growers find it advantageous
to have access to both half- and full-track combines. Half-track combines are used
to open fields and harvest on firmer areas. Full-track machines are useful on soft
ground where half-tracks cannot operate.
The height of the cut should be adjusted low enough to harvest most of the grain,
yet high enough to reduce the amount of straw entering the combine. The peripheral
speed of the reel should be 1- to 1 3/4 times the travel speed of the combine. Rethreshing
wild rice with the tailings return in the combine is not needed. Any material that
was not threshed in the first pass is still attached to the straw and passes out
the discharge over the walkers. The sieves and air flow should be adjusted to allow
only a small amount of material in the tailings-retAdjustment of the air setting
is critical for the separation of grain and straw on the sieves. Excessive air flow
will blow the lighter kernels out the rear of the machine, whereas a low air flow
permits too much light, chaffy material to accumulate with the clean grain. Check
the air passages often for plugging by plant material. The distribution of material
on the walkers and sieves is examined by quickly stopping a combine that is operating
normally by turning off the engine with the machine engaged and applying the brakes.
Clumps of dense plant material on the walkers indicate an inadequate air flow. A
problem may occur in unloading the grain from the combine due to the high moisture
content. Kernels may interlock and cause a bridge in the grain tank. Growers remove
obstructions in the grain tank to reduce bridging.
J. Postharvest Handling and Processing:
Freshly harvested grain has a moisture content of 35 to 45% and proper handling
of the grain is necessary prior to drying to maintain grain quality by preventing
heating and mold growth. Freshly harvested grain should be delivered to the processing
plant as soon as possible. If the grain cannot be transported immediately, it should
be kept cool by refrigeration or adding water and stirring. The expanded commercial
production of wild rice has led to great changes in the processing sector of this
industry. Before commercial production of wild rice began, there were many small
processing plants located in the Great Lakes area that used a variety of homemade
devices. Today, most of the larger processing plants are in Minnesota with additional
ones located in California and southern Canada. Some of the newer plants are capable
of processing more than 6 million pounds of wild rice during the several weeks of
the harvest season.
Most wild rice is processed on a custom basis. Processing fees and the method of
charging for this procedure vary. Some processors charge on a freshly harvested
(green) basis and others on a finished (processed) basis. Charging for processing
on a green basis is potentially disadvantageous to the grain owner since it gives
processors little incentive to maximize the yield of finished grain. Alternatively,
charging on a finished basis can penalize processors if grain yield is lower than
expected. Processing charges range from 18.5 to 85 cents/lb of finished grain, with
the average price being between 40 to 50 cents/lb. The wide range in processing
fees is due to the variation in processing efficiency. Large operations can handle
greater volumes than small plants, which will still process quantities as small
as 100 lb.s small as 100 lb.
The steps in processing involve the separation of immature kernels, fermentation
or curing, drying or parching, hulling, scarification, cleaning, grading, and packaging.
Fermentation is necessary to partially degrade the hulls to permit easier hulling,
impart some of the characteristic flavor of wild rice, and change the immature kernels
from a green to a brown color. Scarification removes part of the outer impermeable
layer, which reduces the cooking time, so it is similar to that of rice. Uniformity
of cooking times is important for wild rice and rice marketed as blends. These processing
steps are common to all major plants with the exception of the separation of immature
kernels and the packaging. Most plants store processed wild rice in 100 lb sacks
in clean, dry warehouses. Several processors put wild rice in small packages and
some make blends of wild rice and rice according to customer specifications. For
more detailed information on processing wild rice, consult the University of Minnesota
production guide for wild rice, or the recent work by Oelke and Boedicker (1991).
VI. Yield Potential and Performance Results:
One hundred pounds of unprocessed wild rice will usually yield 40 lb of processed
grain. Yields of unprocessed grain from shattering types grown in paddies have ranged
from 150 to 200 lb/acre. With shattering-resistant varieties, yields as high as
1,500 lb/acre of unprocessed grain have been reported in Minnesota. Average yields
of varieties from experimental trials in Minnesota during 1981 to 1986 ranged from
1,078 to 1,613 lb of unprocessed grain per acre (Table 3).
VII. Economics of Production and Markets:
The cost of preparing a site for wild rice production will vary considerably depending
on the amount of trees and brush that needs to be removed before ditching and diking.
In addition, the amount of land leveling will vary. Preparation costs, which include
the water pumping and control system can range from $500 to $1,500 an acre.
The cash production costs will vary for each field depending on the year of production.
The cash costs for a new field are higher because of the initial seed cost which
is about $80 an acre (40 lb/acre seed). However, there are added costs such as airboat
thinning and more nitrogen fertilizer for second and third year fields. First year
fields will often yield more, thus compensating for the increased seed cost. The
cash costs for the first year are
approximately $360 with a return of $508 (290 lb/acre of processed grain X $1.75).
Some growers sell their grain before processing for about $0.60/lb giving a return
of $435 (725 lb/acre X $0.60), thereby eliminating the processing cost.
The marketing system for wild rice consists of five major groups: harvesters and
growers, buyers, processors, wholesalers, and retailers. Wild rice from natural
stands is often purchased by buyers at the harvest site on a commission basis for
a processor or wholesaler. Some buyers are brokers, while other buyers purchase
the grain and process it themselves. Over 80% of the cultivated wild rice produced
in Minnesota is marketed by three cooperatives: United Wild Rice, Minnesota Wild
Rice Growers (MRG), and New Frontier Foods, Inc. They either sell unprocessed or
processed grain directly to processors, wholesalers or food companies. Two major
buyers are Busch Agricultural Resources, Inc. and Uncle Bens, Inc.
Wild rice was an expensive gourmet food when the only source was from natural stands.
The growth of wild rice as a field crop coincided with the market expansion, which
resulted in lower prices and a more consistent supply. Since 1968 the wholesale
price of processed wild rice per pound has ranged from a low of $2.10 in 1987 to
a high of $5.15 in 1978. Price variations between 1968 and 1977 were due to limited
and erratic supplies from lake harvests and the initial years of paddy production.
The high prices during 1978 to 1980 were due to attempts by marketers to withhold
supply, and were short-lived since high prices encouraged increased production.
Production expansion in Minnesota was moderate during 1978 to 1980, while in California,
production doubled annually through 1981. High costs of grain storage forced the
sale of stocks by 1981, and consequently, prices returned to market-determined levels.
Production increased 26% each year between 1982 to 1984, yet markets were able to
absorb this increase with only a slight drop in price. In 1985, California production
more than doubled over the 1984 level, and prices have since declined sharply. In
1991 the price to growers for processed grain averaged $1.75/lb.
Markets for wild rice have expanded at a vigorous rate since 1978, especially during
1982 to 1984 when the demand increased 52%. Market expansion has been due in large
part to the introduction of wild rice blends. Although the blends usually contain
only 15% wild rice, they make up over two-thirds of the total sales of wild rice.
If blends had not been introduced, perhaps the industry for field-grown wild rice
would not have developed. Sales in the blend market have increased an average of
15% each year since 1961 when the first blend of wild rice, long-grain rice, and
herbs was sold. Pure wild rice and blends have seasonal and geographic sales trends.
Consumers purchase more pure wild rice in Minnesota than elsewhere due to a greater
familiarity with this food, lower prices, and shipment out of the state as gifts.
The demand for wild rice is expected to increase substantially in the future as
prices stabilize and production expands.
VIII. Information Sources:
Wild Rice: Nutritional Review. 1976. R.A. Anderson, Cereal Chemistry 53:945-955.
Insects of Wild Rice in Minnesota. 1981. A.G. Peterson, D.M. Noetzel, J.E. Sargent,
P.E. Hanson, C.B. Johnson, and A.T. Soemawinata. Misc. Report 157 (AD-MR-2122),
Minnesota Agricultural Experiment Station, University of Minnesota.
Wild Rice Production in Minnesota. 1982. E. Oelke, J. Grava, D. Noetzel, D. Barron,
J. Percich, C. Schertz, J. Strait, and R. Stucker. Agr. Ext. Serv., Univ. of Minnesota,
A Guide to Wild Rice Production. 1984. Agriculture Manitoba, Agdex 116, Manitoba
Agriculture, 29 pp.
Wild Rice Production, Pricing, and Marketing. 1984. E.H. Winchell and R.P. Dahl.
Agr. Exp. Sta., Univ. of Minnesota, Misc. Pub. 29, 35 pp.
The Wild Rice Industry: Economic Analysis of Rapid Growth and Implications for Minnesota.
1986. R.N. Nelson and R.P. Dahl. Staff Paper P86-25, Dept. of Agricultural and Applied
Economics, University of Minnesota, St. Paul, MN.
Wild Rice in Canada. 1988. S.G. Aiken, P.F. Lee, D. Punter, and J.M. Stewart. Agriculture
Canada Publication 1830, Toronto, 130 pp.
The Domestication of American Wild rice (Zizania palustris, Poaceae). 1989.
P.M. Hayes, R.E. Stucker, and G.G. Wandrey. Economic Botany 43(2):203-214.
Fertilizer Recommendations for Agronomic Crops in Minnesota. 1990. G. Rehm and M.
Schmitt, University of Minnesota, AG-MI-3901 1990.
Varietal Trials of Selected Farm Crops. 1991. Minnesota Report 221-1991 (AD-MR-5615-E).
Minnesota Agricultural Experiment Station, University of Minnesota, p. 19.
Wild Rice: Processing and Utilization. 1991. E.A. Oelke and J.J. Boedicker, Chp.
10, pp. 401-439. In: K.J. Lorenz and K. Kulp (eds.), Handbook of Cereal Science and
Technology, Marcel Dekker, Inc., NY.
The information given in this publication is for educational purposes only. Reference
to commercial products or trade names is made with the understanding that no endorsement
for one product over similar products is implied by the Minnesota and Wisconsin