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Alternative Field Crops Manual


E.S. Oplinger1, L.L. Hardman2, A.R. Kaminski1, S.M. Combs1, and J.D. Doll1

1Departments of Agronomy and Soil Science, College of Agricultural and Life Sciences and Cooperative Extension Service, University of Wisconsin–Madison WI 53706.
2Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108. May, 1990.

I. History:

The mungbean, Vigna radiata (L.) Wilczek has been grown in India since ancient times. It is still widely grown in southeast Asia, Africa, South America and Australia. It was apparently grown in the United States as early as 1835 as the Chickasaw pea. It is also referred to as green gram, golden gram and chop suey bean. Mungbeans are grown widely for use as a human food (as dry beans or fresh sprouts), but can be used as a green manure crop and as forage for livestock. Virtually all the domestic production of mungbean is in Oklahoma. Fifteen to twenty million pounds of mungbean are consumed annually in the United States and nearly 75 percent of this is imported.

II. Uses:

Mungbean seeds are sprouted for fresh use or canned for shipment to restaurants. Sprouts are high in protein (21%–28%), calcium, phosphorus and certain vitamins. Because they are easily digested they replace scarce animal protein in human diets in tropical areas of the world. Because of their major use as sprouts, a high quality seed with excellent germination is required. The food industry likes to obtain about 9 or 10 grams of fresh sprouts for each gram of seed. Larger seed with a glassy, green color seems to be preferred.

If the mungbean seed does not meet sprouting standards it can be used as a livestock food with about 1.5 ton of mungbean being equivalent to 1.0 tons of soybean meal for protein content. Feeding trials have been conducted at Oklahoma State University for swine and young calves with good results.

III. Growth Habits:

Mungbeans are in the Legume family of plants and are closely related to adzuki and cowpea (in the same genus but different species). They are warm season annuals, highly branched and having trifoliate leaves like the other legumes. Both upright and vine types of growth habit occur in mungbean, with plants varying from one to five feet in length. The pale yellow flowers are borne in clusters of 12–15 near the top of the plant. Mature pods are variable in color (yellowish-brown to black), about five inches long, and contain 10 to 15 seeds. Self pollination occurs so insect and wind are not required. Mature seed colors can be yellow, brown, mottled black or green, depending upon variety. These round to oblong seeds vary in size from 6,000 to over 12,000 per pound, depending upon variety. Germination is epigeal with the cotyledons and stem emerging from the seedbed.

IV. Environment Requirements:

A. Climate:

Mungbeans are a warm season crop requiring 90–120 days of frost free conditions from planting to maturity (depends on variety). Adequate rainfall is required from flowering to late pod fill in order to ensure good yield. Late plantings which result in flowering during the high temperature-low moisture period in July and August will reduce yield. High humidity and excess rainfall late in the season can result in disease problems and harvesting losses due to delayed maturity.

Mungbeans (if proper varieties are used) are adapted to the same climatic areas as soybean, drybean and cowpea. Mungbeans are responsive to length of daylight so short days hasten flowering and long days delay it. Varieties differ in their photoperiod response.

B. Soil:

Mungbeans do best on fertile sandy, loam soils with good internal drainage. They do poorly on heavy clay soils with poor drainage. Performance is best on soils with a pH between 6.2 and 7.2 and plants can show severe iron chlorosis symptoms and certain micronutrient deficiencies on more alkaline soils. Mungbean has phosphorus, potassium, calcium, magnesium and sulfur requirements similar to other legumes which must be met by fertilizer additions if the soil is deficient in these elements.

C. Seed Preparation and Germination:

Because the major use of mungbean is for sprouts; excellent germination must be maintained by careful harvesting and storage systems. Seed is not generally treated with fungicides, insecticides or bactericides because of the possibility of ingestion of treated seed.

Because the seed is small, careful handling and attention to planting machinery adjustments is necessary to ensure planting with little damage to the seed.

If mungbean is being planted in a field for the first time the proper nitrogen fixing bacteria must be provided. This inoculant can be applied to the seed just before planting or applied in the furrow in peat or granular form. Care must be taken to distribute this inoculant uniformly in the field. Be sure to use the bacteria that is specific for mungbean or closely related species.

Only certified seed should be used so that quality and variety purity are guaranteed. Currently Oklahoma Slate University Crop Improvement Association is a source of foundation and certified seed of certain varieties, some of which may be adapted to this area.

V. Cultural Practices:

A. Seedbed Preparation:

The soil should be tilled to remove weeds and to prepare a seedbed which will provide good seed-soil contact. The final seedbed needs to firm with a surface free of clods and debris to allow a good distribution of seeds. If moisture is short, keep preplant tillage to a minimum to prevent drying out the top two or three inches.

B. Seeding Date:

Mungbean should be planted between May 15 and June 6 like the other legumes (field bean, adzuki, cowpea) which are being grown as the major crop on the field. Too late a planting date results in bloom and pod fill during the hottest, driest period of the summer. In some areas mungbean is planted as a second crop after the small grain is harvested. If this is done planting should occur immediately after the grain harvest with a minimal disturbance of the seedbed. It is doubtful that the growing season in Wisconsin and Minnesota would be long enough to plant after small grain harvest.

C. Method and Rate of Seeding:

Seeds should be planted 1 1/2" deep in a well prepared seedbed with a good moisture content. If the surface layers are dry this depth can be increased to 3" if the soil type is one which does not crust easily. The seedlings of mungbean can have a hard time breaking through a thick crust and stands will be reduced.

Planting equipment for soybean, fieldbean, adzuki and cowpea can be used to plant mungbean but careful adjustments must be made to properly deliver and distribute the very small seed (6,000–12,000 seeds/lb). In 30" rows the recommended planting rate is 9 seeds/ft; in 20" rows 6 seeds/ft.; and in 6"–10" rows 2–3 seeds/ft. Populations of 150,000–200,000 plants per acre will be achieved with these rates.

Because of possible weed outbreaks with early season planting and the need for cultivation to control them, row spacings of 20"–30" are recommended. In later plantings or planting as a second crop the narrow rows will produce higher yields.

D. Fertility and Lime Requirements:

Mungbeans require phosphorus, potassium and certain micronutrients at levels similar to other field beans. The amount to add as fertilizer should be based on soil test levels. organic matter content and projected yield level. Phosphorus and potassium recommendations for Minnesota and Wisconsin are given in Table 1.

If the field has been previously inoculated with the proper Rhizobium for nitrogen fixation, additional nitrogen is not required. However some growers provide 30–50 lbs of N to assist in early plant establishment, especially on sandier soils. Like the other legumes most of the nutrient uptake occurs later in the season so starter fertilizers have not been very helpful.

Mungbean require slightly acid soil for best growth. If they are grown in rotation, lime for the pH of the most acid sensitive crop. If soil pH is below 6.3, lime should be added to raise pH to the desired level. For best results, lime should be applied one year prior to growing mungbeans and thoroughly incorporated.

Table 1. Phosphorus (P) and Potassium (K) recommendations for mungbeans.

P Soil Test (lb./acre)1K Soil Test (lb./acre)1
Expected Yield0–1011–2021–3030+0–100101–200201–300300+
(lb./acre)P2O5 to apply2 (lb./acre)K2O to apply2 (lb./acre)
3000 or more806040012090500
1400 or less403000603000
1For soil P and K reports in ppm. (ppm x 2 = lb./acre).
2Recommended rates are for total amount to apply—broadcast + row. Low rates may be row-applied.

E. Variety Selection:

Hundreds of experimental lines of mungbean have been tested in the United States (primarily at Texas A & M University, Oklahoma State University and the University of Missouri) over the years. Much of this testing and research has been coordinated with the Asian Vegetable Research and Development Center in Taiwan which is the international center responsible for mungbean research worldwide. A few years ago some work on mungbean was also being done at the Morden, Manitoba research station for Agriculture Canada, especially looking for earlier maturing, upright growth habit varieties.

Maturity, upright versus prostrate growth habits, small versus large seed types and color of seed are important attributes to be considered when selecting a variety. The sprouting industry desires a superior germination rate of the seed to produce a thick, crisp, white colored hypocotyl with a minimum of roots present. There are varietal differences for several of these characteristics.

Currently the only breeding programs are at Oklahoma State and Texas A & M Universities, but some private seed companies have seed of certain varieties of their own.

All of the varieties provided by these programs may not be adaptable in the Upper Midwest, so a grower should be careful about using them without a certain amount of testing.

F. Weed Control:

1. Mechanical: Rotary hoeing and/or field cultivation should be used as required to remove weed competition until flowering begins. Later emerging weeds are not as damaging to yield as the early ones. Avoid cultivation in the field when the plants are still damp because this can spread bacterial and fungal disease. Growers planting mungbean for the first time should plan on using wider row spacings so that cultivation can be done if weeds become a problem.

2. Chemical: Dual (metolachlor) is approved for preemerge or preplant incorporate use and Treflan (trifluralin) is available for preplant incorporate use. Both herbicides give excellent grass control and fair to good suppression of annual broadleaves. Follow label directions to select the appropriate rate for your soil type and organic matter content. Currently no postemerge chemicals are available for control of later emerging weeds. Broadleaf weed control is difficult because many of the chemicals damage the mungbean. It is hard to get label clearance for a minor crop like mungbean, but it may fit under the dry pod crop grouping of certain labels already cleared. Check with your local Extension agent, consultant or chemical company representative before using any chemical on mungbean.

Because mungbean are eaten directly by humans the label restrictions are quite strict as to use and timing of all chemicals applied to the crop.

G. Diseases and Their Control:

Mungbeans are susceptible to the usual array of pathogens which attack other legumes such as white mold, Phytophthora, mildew, bacterial rots, Rhizoctonia, etc.

Proper rotation, tillage practices, and water management (if under irrigation) can be effective in reducing the impact of these diseases. Contact your Extension agent or crop consultant for assistance.

H. Insects and Other Predators and Their Control:

Mungbeans do not generally require insecticide sprays to control problems in the field. Seed corn maggot and wireworms could attack seeds in the early germination period and reduce stand under certain conditions. Occasional grasshopper or caterpillar infestation could occur and result in defoliation. Mungbeans are no more affected by insect problems than the other legumes. Weevils can attack the seed in storage.

I. Harvesting:

Pod maturity in mungbean is not uniform because the plants flower over an extended period. This makes it difficult to decide when to harvest. Generally harvest should begin when one half to two-thirds of the pods are mature. Seeds might be between 13%–15% moisture at this time. Some growers swath the plants to allow further maturity of the pods and then combine using a pick up header on a small grain combine. This is an especially useful harvest system for the vine type varieties or when there is delayed maturity or problem weeds present. Swathing should be done earlier in the day to prevent severe shatter losses.

Direct combining can be done in weed free, uniformly mature fields of the upright growth habit type of mungbean. It is also important to adjust the cylinder speed and concave clearance for complete threshing with a minimum of seed breakage. After combining the seed should be quickly cleaned to remove green pods, leaf material, debris, etc. which could create drying and storage problems. In developing countries, the mungbeans are handpicked as the pods mature. As many as five pickings are done on some high yielding lines.

J. Drying and Storage:

Prior to storing, remove all leaf material, stems, immature pods, dirt, insect parts and other debris. Mungbeans at about 12% moisture can then be stored in regular grain bins previously fumigated to control bean weevils. If beans are higher in moisture then 12% they can be dried slightly by moving unheated air though thin layers until they are near the 12% value. Because they will be sprouted and eaten direct, care should be taken to keep all possible contaminants away from the storage area.

VI. Yield Potential and Performance Results:

The yields of mungbeans depend largely on weather conditions, soil, cultural practices, and variety. Yields can range from 300 to over 2,000 pounds per acre. Yields from second crop plantings are not as large as main crop yields.

VII. Economics of Production and Markets:

Production costs for mungbeans in the Upper Midwest have not been determined, but the cash costs should be about the same as navy, pinto, adzuki, cowpea or soybean. Because of the lack of locally available seed sources, seed cost will likely be slightly higher.

As with all specialty crops with limited market uses, a grower should always identify markets before producing mungbeans on a large scale. Contact price varies widely but is likely to be in the same general area as adzuki, navy and pinto contracts. Local health food stores, restaurants and brokers may be able to purchase your production.

VIII. Information Sources:

References to pesticide products in this publication are for your convenience and are not an endorsement of one product over other similar products. You are responsible for using pesticides according to the manufacturer's current label directions. Follow directions exactly to protect the environment and people from pesticide exposure. Failure to do so violates the law.

Last update November 21, 1997