E.S. Oplinger1, L.L. Hardman2, A.R. Kaminski1, K.A. Kelling1, and J.D. Doll1

1 Departments of Agronomy and Soil Science, College of Agricultural and Life Sciences and Cooperative Extension Service, University of Wisconsin-Madison, WI 53706.

2 Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108.
May, 1990.

I. History:

Lentil (Lens culinaris Medik.) may have been one of the first agricultural crops grown more than 8,500 years ago. Production of this cool season annual crop spread from the Near East to the Mediterranean area, Asia, Europe and finally the Western Hemisphere. It may have been introduced to the United States in the early 1900s. The crop has received little research attention to improve its yield and quality. It grows well in limited rainfall areas of the world.

Lentil is a pulse (grain legume) crop. In North America much of the acreage is in eastern Washington, northern Idaho, and western Canada where drier growing season conditions prevail. It has been grown in that area since the 1930s as a rotation crop with wheat. Most of the lentil production in the United States and Canada is exported, but domestic consumption is increasing.

II. Uses:

Lentil is a protein/calorie crop. Protein content ranges from 22 to 35%, but the nutritional value is low because lentil is deficient in the amino acids methionine and cystine. Lentil is an excellent supplement to cereal grain diets because of its good protein/ carbohydrate content. It is used in soups, stews, casseroles and salad dishes. Sometimes they are difficult to cook because of the hard seed coat that results from excessively dry production conditions.

Lentils which fail to meet food grade standards (graded #3 or below) can be used as livestock feed because of their high protein content and lack of digestive inhibitors.

Lentil can be used as a green manure crop and one particular Canadian variety, Indianhead, provides a large amount of fixed nitrogen (estimated to be 20 lb/acre).

III. Growth Habits:

Lentil plants are slender, semi-erect annuals with compound leaves (4 to 7 pairs of leaflets) with a tendril at the tips. Plants normally range from 12 to 20 in. tall, the taller plants resulting from cool growing season temperatures, good moisture and good fertility. Plants can have single stems or many branches depending upon the population in the field.

Flowering begins on the lowest branches, gradually moving up the plant and continuing until harvest. Each flower produces a short pod containing one or two lens-shaped seeds. Flowers can be white, lilac or pale blue in color and are self-pollinated. At maturity plants tend to lodge because of their weak stems.

Lentil produced in North America has larger seeds than that from India and the Near East. The seeds (2 to 7mm in diameter) come in colors of tan, brown, or black, and some varieties produce purple or black mottled seeds. Lentil seed number varies from 15,600 to 100,000 seeds/lb.

IV. Environment Requirements:

A. Climate:

Lentil is adapted to cool growing conditions, and the young plants are tolerant of spring frosts. This allows for early spring planting dates.

Lentils have been grown extensively in the semi-arid parts of the world, where they have slightly lower yields, but good seed quality. High humidity and excessive rainfall during the season encourages vegetative growth, which prevents good yield and can reduce seed quality. Ten to twelve in. of annual rainfall will produce high yields of good quality seed. Excessive drought and/or high temperatures during the flowering and pod-fill period also reduce yields.

B. Soil:

Lentil is adapted to all soil types, from sand to clay loam, if there is good internal drainage. Lentil does not tolerate flooded or waterlogged soils, and does best on deep, sandy loam soils high in phosphorus and potassium. Good drainage is required, because even short periods of exposure to waterlogged or flooded field conditions kill plants. A soil pH near 7.0 is best for lentil production.

C. Seed Preparation and Germination:

Unless nodulated field pea or lentil has been grown recently on a field, the seed should be inoculated with Rhizobium leguminosarum just prior to planting (within 24 hours). Follow the instructions for inoculation, and protect treated seed from high temperatures and drying winds until planted. Various forms of inoculant are available, some of which can be placed in the furrow with the seed.

Good quality lentil seed does not need to be treated with insecticides or fungicides, because it germinates rapidly and seedlings emerge quickly. Seed treatment compounds can interfere with the nodulation process.

V. Cultural Practices:

A. Seedbed Preparation:

A firm, smooth seedbed with most of the previous crop residue incorporated is best for lentil. Uneven surfaces, large clods, rocks or protruding crop residue can interfere with seed placement and complicate later swathing and combining.

B. Seeding Date:

Lentil should be seeded in late April to early May, when small grain is being planted. Later seeding dates produce shorter plants and late maturing pods which increase harvest losses.

C. Method and Rate of Seeding:

Lentil should be planted 12 in. deep, but this can be increased to 22 in. when the upper layers of soil are excessively dry at planting time. Because of the small seed size of some varieties, lentil cannot emerge if planted too deep or if the soil has crusted extensively. Lentil has hypogeal emergence, which means that the growing point emerges but the cotyledons remain in the soil.

Seeding rates vary depending upon seed size, but a target population of 400,000 plants/acre should be reasonable. This could require between 30 and 80 lb/acre of seed, depending upon variety and seed size. This would provide about 20 plants/square ft.

Because of the fragile growth habit of lentil and the fact that the crop does not compete well with weeds, the best yields are from fields planted with a grain drill which can ensure proper depth and distribution as well as good seed-soil contact. Because of seed size variation, care must be taken to calibrate the drill properly.

D. Fertility and Lime Requirements:

Inoculation with the proper Rhizobium will provide the nitrogen requirements of lentil. However, if available nitrogen is low (organic matter less than 2%), an early nitrogen supplement of about 30 to 40 lb/acre is required to sustain the young plants until root nodulation develops. If applied as starter, this material should be applied adjacent to but not in contact with the seed. Smaller amounts of N (10 to 30 lb/acre) may provide some benefit on higher organic matter soils, especially where drainage is somewhat restricted. Care should be taken not to provide too much nitrogen, which could inhibit nodulation and produce excessive vegetative growth at the expense of seed yield.

As for most legumes, sulfur needs are medium to high, and responses may be seen on light colored sandy soils where manure has not been applied.

Phosphorus and potassium are recommended for maximum yields on soils testing medium or low. Optimum soil tests range 15 to 30 ppm (30 to 60 lb/acre) for P and 90 to 120 ppm (180 to 240 lb/acre) for K for most soils. Band applications of P may be of some benefit on very low P or high pH (above 7.6) soils.

Lime needs for lentil have not been well established. However, it is likely similar to that of other leguminous vegetables -- 6.0 on mineral soils and 5.6 on organic soils.

E. Variety Selection:

Growers should consider maturity, growth habit, seed size and color as well as yield potential when selecting a variety of lentil. Currently buyers prefer lentils with larger seeds that are light in color and without mottling on the seed coat.

Several varieties have been tested in research conducted by University of Minnesota scientists. (See Table 1 for performance data of these varieties.)

Table 1: Characteristics and seed yield of Lentil varieties.
  Planting to
bloom maturity
  -------- lb/acre -------- No./lb %2 inches score3 ------ days ------
Brewer4 943 2031 1357 8,890 27.4 18 4.9 60 111
Chilean 785 750 --- 1226 9,650 26.5 19 4.8 61 110
Eston 1029 1733 1650 15,120 25.1 17 3.4 63 113
Jasper6 1043 1525 --- 15,120 26.5 17 3.8 63 116
Laird7 343 1344 820 7,440 24.2 21 3.5 67 115
Primera6 554 1895 --- 5,670 28.3 18 4.9 64 119
Red Chief4 757 1673 1574 9,070 26.7 18 5.6 60 111
1irrigated; 2oven-dry; 31=erect, 9=flat; 41982-85; 51982-84; 61985; 71981-84.

The USDA Plant Introduction Station at Pullman, Washington, has tested large numbers of lines from all over the world and scientists there continue to evaluate and develop new varieties. Some of the Canadian research centers also are releasing new varieties. For the latest information on new and old variety performance, contact your local extension office or crop consultant.

F. Weed Control:

Lentil is not very competitive (especially as seedlings) with many of the grasses and/or broadleaf weed species that infest farm fields, so weed control before planting and early in the growing season is critical.

Mechanical: Harrowing or rotary hoeing fields after emergence is recommended only if there is a serious weed problem. Because of the slender early stem growth, the plants are easily damaged at this time. If harrowing or hoeing is planned, be sure to use the recommended seeding rates discussed earlier because the plant stand will be reduced slightly along with the weeds. Rotary hoeing is normally done 7 to 10 days after seeding.

Chemical: Roundup (glyphosate) can be used as a preplow treatment in the fall or spring to control quackgrass. Apply 1 qt/acre in 5 to 10 gal/acre of water when the quackgrass is 6 to 8 in. tall and actively growing. Fall treatment is encouraged, as planting will be delayed with spring applications. To control annual grasses, Poast (sethoxydim) can be used in postemergence treatment when the grasses are 4 to 6 in. tall. A rate of 1 pt/acre controls many annual grasses; check the label and select the rate appropriate for your weed species. Always use 1 qt/acre of Dash or a crop oil concentrate when Poast is applied.

G. Diseases and Their Control:

Because most of the lentil production in the United States is in the dryer, less humid environments of the west, the crop is relatively free from major diseases.

Ascochyta blight, Sclerotinia (white mold), Fusarium root rot and Rhizoctonia root rot are possible disease problems for lentil. Since no effective treatment is available for these diseases, crop rotation is the most effective method of preventing a disease problem.

Avoid fababean, fieldbean, field pea, mustard, canola, rapeseed, soybean, sunflower, sugar beet and potato in too close a rotation, because these crops are susceptible to the same diseases. Corn and small grains are good rotation crops in conjunction with lentil. Some scientists feel a three to four-year rotation away from lentil is best for reducing disease problems. Always use good quality disease-free seed to prevent introduction of disease into clean fields.

H. Insects and Other Predators:

Lentil can be attacked by aphids, thrips, Lygus bugs, seedcorn maggots and wireworms, but major problems from these insects are seldom noted. If a serious problem is developing in a field, you should consult your local Extension office for information about obtaining threshold values and recommendations for control.

I. Harvesting:

Lentil should be swathed when plants begin to turn yellow and the lower pods become brown to yellow-brown in color. This will occur within several days and should be carefully watched, as pods can readily shatter. Lentil should be swathed when there is sufficient moisture to toughen the pods. Swathing should not be done during hot, dry periods of the day.

Lentil has a weak stalk and tends to lodge badly. This means that a low cut is required in order to minimize losses. Windrowing can be a very slow and difficult operation. A dry field surface which is level, firm and free of stones is necessary to reduce harvesting difficulties.

A pick-up reel and lifter guards are very helpful when windrowing. A floating cutterbar mounted on a windrower can further minimize windrowing losses and difficulties.

Depending on the weather, windrowed lentil may take a week or more to dry down. Since the lentil windrow has no strong stubble to hold it off the ground, air circulation through the windrow is poor. This may result in seed discoloration and mold development during periods of extended wet weather.

Lentils are considered dry at 14% moisture content. Combining at this moisture level can result in high losses and damaged seeds. It may be advisable to combine at a higher moisture content of 18 to 20%, and dry artificially.

If the field is uniformly mature, it is possible to combine lentil directly. This should only be attempted at moisture levels of 18 to 20%, to prevent excessive pre-harvest shattering. A combine equipped with a floating cutterbar should be used to minimize header losses.

Once in the combine, lentils thresh easily. Compared to wheat settings a slower cylinder speed is necessary to prevent cracking, and the concaves should be set wider. Initial wind and sieve settings for wheat may be used.

J. Drying and Storage:

If lentil seed is harvested at moisture contents greater than 14%, it will have to be dried to prevent heating and molding in storage. It is best to let the seed dry down in the field, if the drier plant material can be handled by the combines without major losses due to shattering of the pods.

Lentils can be dried in heated air dryers, but a maximum temperature of 110oF is recommended to reduce cracking of seed coats. Natural air drying has advantages over heated air, but proper design of the system is necessary. The design must ensure good airflow through the seed, which usually means that thinner layers of the seed must be used in this process.

VI. Yield Potential and Performance Results:

Yields vary with variety, management and environmental conditions. Under good research management and excellent growing conditions, lentil has yielded in excess of 2,000 lb/acre. In production fields growers should be able to expect 1,000 to 1,500 lb/acre yields. Yields in research trials in Minnesota (see Table 1) have ranged from 343 to 2,031 lb/acre, depending upon variety and location.

VII. Economics of Production and Markets:

The price of lentil has varied widely in recent years, ranging from $.15 to $.35/lb. This is a direct reflection of the volatile nature of world prices for this commodity. With favorable prices, lentil has provided a very attractive alternative crop for good producers. Seed damage, presence of foreign material and high moisture content will reduce the grade of lentil and result in a lower price. As with other specialty crops, growers should always locate markets and delivery points and determine a suitable price before planting a new crop.

VIII. Information Sources:

Grain Legumes As Alternative Crops. 1987. Proceedings of a symposium sponsored by The Center For Alternative Crops & Products University of Minnesota. July 23-24, 1987. 194 pages.

Growing Lentils in Washington. 1968. Extension Bulletin 590, Cooperative Extension Service, Washington State University, Pullman, WA.

Lentils: A Potential Montana Specialty Crop, Bulletin MT 8905, Montana State University Extension Service. Bozeman, MT.

Lentil Production in Alberta. 1980. Agdex 142/25-5 Alberta, Agriculture.

Lentil Production in Manitoba. 1982. Agdex 147 Manitoba Agriculture.

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 discrimination is intended and no endorsement by the Minnesota or Wisconsin Extension Services is implied.

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