Comprehensive Guide to Dry Beans Production

January 17, 2023 Globalinfo247

Known as a “nutritional powerhouse,” Dry beans (Phaseolus vulgaris L.) are a human food high in protein, phosphorus, zinc, iron, vitamin B1 and fiber, among many other nutritional traits. Dry beans are an important staple food in many areas of the world, especially in Central and South America, and Africa.

They are the most important legume worldwide for human consumption. Different cultures have developed a multitude of end products made with dry bean.

Dry bean is a major cash crop in the Northarvest Bean Growers Association growing region of North Dakota and Minnesota and has been grown on a large scale since the 1970s. The region is the largest producer of dry beans in the U.S. Most of the production is in the eastern half of North Dakota, with the major production area in the northeastern quadrant.

Pinto is the most important market class in North Dakota, based on acreage and value, followed by navy and black bean. These three market classes account for approximately 95% of the total acres of production. Kidney, pink, small red, cranberry and others are grown on limited acres.

Dry beans are a food crop that requires the producers to provide special cultural management and attention. Proper management is essential from cultivar selection, field selection and planting through harvest, plus marketing for maximum profitability as a human food product. We recommend obtaining a marketing contract.

Dry Beans Cultivar Selection

When selecting a high-yielding and good-quality cultivar, use data that summarize several years and locations. Choose a high-quality cultivar that, on average, performs the best at multiple locations near your farm during several years. Tables 1 through 4 provide information about selected bean cultivars.

Dry Beans Types and Development Stages

Two basic plant growth habits are found in dry edible bean: determinate (bush) or indeterminate (vining or trailing). Cultivars may be classified according to plant growth habits (Tables 1 to 4). For example, navy beans may be the bush or vining type.

With the determinate habit, stem elongation ceases when the terminal flower racemes of the main stem or lateral branches have developed. With the indeterminate habit, flowering and pod filling will continue simultaneously or alternately as long as temperature and moisture availability permits growth to occur. The growth of the plant will terminate after a killing frost.

In addition to the distinction between determinate and indeterminate plant habits, four plant growth types have been identified. These are: Type I – determinate bush; Type II – indeterminate upright short vine, narrow plant profile, three to four branches; Type III – indeterminate, prostrate vine; Type IV – indeterminate with strong climbing tendencies requiring trellis systems for optimal production.

Most cultivars in the U.S. belong to the first three plant growth types. These refined growth types have become useful in the identification and classification of newer upright bean cultivars.

The development of new cultivars that combine upright architecture (Type II) and competitive yields have allowed many growers to switch their harvest operation from conventional to direct harvest (two- or three-step vs. one-step operation).

This allows for faster harvest, along with a reduction in time, equipment and labor. In addition, it allows for a better harvest timing among different crops, which is crucial in this region.

About 50% of the growers direct combine all their fields and 20% of the growers do not direct combine at all. In other cases, farmers direct combine some and conventionally harvest the remaining of their bean acres (“2018 Dry Bean Grower Survey,” NDSU publication E1902).

However, seed losses during harvest in many cases may be higher with direct harvest because of pods located close to the ground and increased shattering. Fifty-five percent of the growers report yield losses between 1% and 5%, and 33% of the growers report losses of 6% to 10%. This compares with 80% of the growers reporting 1% to 5% yield loss with conventional harvest methods.

These direct-combine seed losses can be minimized by choosing the appropriate cultivar and having the optimal setup in the harvest equipment. In addition, the environmental conditions at the time of harvest (soil conditions, plant and seed moisture and temperature, among others) are also important factors that influence the amount of seed losses.

Plant development for determinate and indeterminate plant types has been divided into vegetative (V) and reproductive (R) stages, as indicated in Table 5. Vegetative stages are determined by counting the number of trifoliolate leaves (V1 to Vn) on the main stem beginning above the unifoliolate leaf. Reproductive stages are described with pod and seed characters in addition to nodes. The first pod developing on the plant is described and followed to maturity.

At the time of first flower (reproductive stage indicated by R), secondary branching begins in the axis of lower nodes, which will produce secondary groups of flowers and pods. Following the main stem, which is readily discernible on determinate and indeterminate plants, is important. A node is counted when the edges of the leaflets no longer touch.

A bean plant may have the same number of nodes at two locations but differ in height because of the stem length between nodes. The average days from planting to reach a certain growth stage and days between stages are very broad and will vary from year to year and cultivar to cultivar. Flower color varies among cultivars. Beans normally are self-pollinated, with less than 1% natural out-crossing.

Immature pods of most cultivars are green, turning yellow and then light brown or tan as they mature. An exception is black beans, in which some cultivars may have light purple pods. Pods of the navy beans are more cylindrical, compared with the longer, wider and more flattened pod typical of the pintos.

The pods of dry beans are very fibrous, compared with the pods of snap beans. A satisfactory dry edible bean cultivar bears its pods without touching the soil, ripens uniformly and does not shatter appreciably at maturity.

Table 5. Stages of vegetative and reproductive development in determinate bush (Type I) and indeterminate (Type III) dry beans.

Dry Beans Plant Population

Seed size (Table 6) and established plant populations (Table 7) vary significantly among dry bean market classes. Pinto bean cultivars range from 1,200 to 1,600 seeds per pound. Pinto bean planting rates are recommended to establish early season plant populations of 70,000 to 80,000 plants per acre.

In some instances, reduced yields were observed when pinto plant populations were below the recommended density. For example, averaged across two years at Carrington, yield with plant populations at 58,000 plants per acre was 1,580 pounds per acre, compared with 75,000 plants per acre yielding 1,730 pounds per acre.

The traditional recommendation by NDSU for black and navy bean plant density has been 90,000 plants per acre. Recent research with black beans in eastern North Dakota averaged across eight site-years has indicated only a 3% seed yield increase with 140,000 plants per acre, compared with 100,000 plants per acre.

Navy bean seed yield with 28-inch row spacing had similar yield among plant populations of 93,000, 117,000 and 140,000 plants per acre in a three site-year NDSU study. However, in the same study comparing 14-, 21- and 28-inch rows, the highest navy seed yield was obtained with plant populations greater than 115,000 plants per acre in 14-inch rows.

To obtain desired plant populations, overseed live seed by at least 10% to compensate for losses during emergence. Planting rates should be adjusted for low-germination seed lots or cool, wet planting conditions.

Recommended dry bean planting depth is 1½ to 2½ inches. Growers should test their planter on a hard surface and in the field at normal planting speeds to ensure proper seeding rate and depth.

Dry Beans Row Spacing

According to the NDSU Extension and Northarvest Bean Growers Association grower survey (2018), most pinto, black and navy beans are grown in 21- to 30-inch rows. Also, the majority of black and navy beans are grown in 22-inch rows.

NDSU studies with pinto beans indicate narrower planted rows provide a yield advantage in dryland and irrigated production (Table 8). Also, an NDSU three site-year study with navy bean indicated as rows narrowed from 28 inches to 14 inches, seed yield increased.

However, the same study with black beans indicated no yield difference among 14-, 21- and 28-inch rows. Additional information on black and navy bean row spacing and plant population is available in the NDSU Extension “Black and Navy Bean Response to Row Spacing and Plant Population in Eastern North Dakota” (A1921).

Growing dry beans in narrow rows poses several risks. The more closed canopy increases the potential for disease such as white mold. Narrow rows do not allow between-row cultivation. Also, challenges increase with direct harvest of narrow rows, including increased potential for seed loss.

Soil, Tillage Systems and Requirements for Plant Establishment

Dry beans are adapted to a wide range of soils. Dry beans are not sensitive to soil type as long as the soil is reasonably fertile, well-drained and free of conditions that interfere with germination and plant emergence, such as salinity.

Growing the crop on a well-drained soil is essential because beans are extremely sensitive to standing water or waterlogged conditions. Tile drainage will reduce saturated conditions in the root zone, which will improve plant development.

The majority of dry bean acres are tilled conventionally; however, dry beans can be grown successfully in conservation tillage systems. For example, five site-years of research at Carrington indicate similar seed yield with strip tillage (2,590 pounds per acre), compared with yield with conventional tillage (2,620 pounds per acre).

Winter rye can be used as a cover crop during the prior fall and spring before dry bean plant establishment for benefits including reduction of soil erosion, soil water management, weed suppression and long-term improvement in soil productivity.

Termination timing of rye is based on bean planting date and benefits of extending rye growth, while maintaining adequate soil moisture for bean seed yield. A three-year study at Carrington indicates that with marginal spring soil moisture, rye needs to be terminated two to four weeks before bean planting to maintain yield similar to a conventional bean production system.

Dry bean is a warm-season crop. The optimum average growing temperature is 65 to 75 F but dry bean is adapted to a fairly wide range of temperatures. Dry bean is not tolerant to frost or prolonged exposure to near-freezing temperatures at any stage of plant growth.

Dry beans should be planted when soil temperatures are consistently in the mid 60s F. Typical planting dates in North Dakota generally range from the last 10 days in May to the first 10 days in June. Six site-years of planting date research conducted by NDSU with pinto, black and navy beans indicated no yield advantage with early planting (“Impact of Planting Dates on Dry Edible Bean”, NDSU Extension publication A1806).

Hail Damage

The amount of crop damage caused by hail will depend on the intensity, size of hail stones and duration, as well as plant type and stage of development. Determinate (Type I) cultivars are likely to suffer greater losses than the indeterminate (Types II and III) cultivars because Types II and III can recover and compensate to a greater degree than can Type I.

Severe hail damage can delay plant maturity. The earlier the stage of development at which the injury occurs, the greater the time available for recovery, resulting in less yield reduction. Hail will not directly affect seed quality unless a strike occurs on the pod.

Crop Rotation and Disease Management

Many of the pathogens causing disease on beans are soil-borne and residue-borne. A three-year crop rotation helps reduce inoculum of most pathogens, and a four-year rotation may be recommended if white mold is severe in a field.

However, crop rotation is not a “cure-all” because many pathogens produce spores that are air-borne and may blow in from nearby fields. Field-to-field spore dispersal (and in some cases much greater distances) is most notable of the pathogens that cause white mold and rust. Consequently, field selection is also important; if possible, avoid planting next to a field that was infected severely with rust last year.

Crop rotation may be an effective management tool for disease management. In some cases, a disease such as rust may infect only dry beans, so rotation to any other crop is effective. In other cases, a disease, such as soybean cyst nematode (SCN), may occur on just one other crop.

In the situation of SCN, soybeans and dry beans are susceptible, and rotation to any other crop is effective. However, a pathogen may have an extremely wide host range, such as with Sclerotinia sclerotiorum, which causes white mold on many broadleaf crops and many broadleaf weeds.

The three most important diseases to consider when selecting a crop rotation are white mold, SCN and Rhizoctonia root rot.

White mold

Dry bean, sunflower, canola and lentil are among the most susceptible crops to white mold. White mold also attacks soybean, safflower, mustard, alfalfa, field peas and potatoes. Flax and buckwheat are considered only marginally susceptible.

Regardless of which plant/crop is infected with Sclerotinia, the pathogen produces the same survival structures, called a sclerotia. As a result, an epidemic of white mold on sunflowers can result in an epidemic in dry beans in future years.

Similarly, the pathogen can cause severe white mold on a number of different broadleaf weeds, making good weed control important for management of white mold. Members of the grass family, including small grains, corn and millet, are not susceptible to white mold and are good rotational crops for dry bean disease management.

Rhizoctonia root rot

Rhizoctonia solani causes a root rot of dry bean. Specific Anastomosis groups (strains) of Rhizoctonia solani can cause disease on sugarbeet and soybean. Including these crops in a rotation may lead to the buildup of Rhizoctonia inoculum. One of the Rhizoctonia strains that attacks dry bean, sugarbeet and soybean also attacks flax and lentil.

Soybean cyst nematode

The parasitic worm Heterodera glycines attacks soybean and dry edible bean. SCN eggs may survive in cysts in the soil for many years, and eliminating the nematode using crop rotation is not possible.

If a susceptible crop is planted into a field with SCN, nematode egg levels can increase dramatically in one growing season. Rotation away from soybean and dry beans with any other crop (small grains, corn, sunflower, canola, etc.) will reduce the egg levels in the soil and the likelihood of yield loss.

The benefit of crop rotation for even one year is notable, but greater reduction in eggs levels are seen with two years. If soybean are included in a dry bean rotation, using a SCN-resistant soybean cultivar is critical.

Dry Bean Fertility

Dry beans are responsive to fertilizer when soil fertility levels are inadequate to support yield levels possible with existing soil moisture and growing season climatic conditions.

Soil testing is recommended to determine the probability of crop response to fertilizer amendments. If soil levels are less than adequate, dry beans may respond to nitrogen (N), phosphorus (P), potassium (K) and zinc (Zn) in many northern Plains soils.

Soil test cores should be taken at zero to 6-inch and 6- to 24-inch depths. N is analyzed at both core depths, and P, K and Zn are analyzed on the zero to 6-inch depth.

Salt levels at both depths may be analyzed if a reason exists to suspect a salt problem. Soil pH may be determined on the surface and subsurface depth if iron chlorosis problems are anticipated.

Phosphorus

Soils with soil test levels indicating medium levels and lower would be expected to respond to P fertilizer. Phosphorus fertilizer may be broadcast or banded. Banded rates of P in the very low or low range may be reduced by one-third from Table 9 recommendations because the broadcast recommendations also include extra buildup fertilizer useful in long-term fertility programs.

Reducing the rates will not result in long-term improvement of soil P fertility but may increase short-term profitability in the current crop year. Phosphorus should be applied as recommended in Table 9.

Table 9. Phosphorus recommendations for dry beans.

Recent studies at the Carrington Research Extension Center, for multiple years, showed that low rates of in-furrow or near-furrow 10-34-0 (2 to 3 gallon per acre) have minimal effect on stand and substitute for higher recommended rates of broadcast fertilizer.

This is contrary to previous findings and may be the result of newer cultivars, compared with those used in the past. Using a low rate of 10-34-0 will have substantial economic benefits for farmers whose fields test in the low to very low P categories.

Additional dry bean P starter fertilizer details are available in the NDSU Extension publication “Pinto Bean Response to Phosphorus Starter Fertilizer in East-central North Dakota” (A1883).

Potassium

Potassium (K) seldom is required in most northern Plains soils; however, a soil test should be analyzed to determine the probability of response. Soils with medium K level or lower may respond to K fertilizer.

Lower K levels sometimes may be found on sandy ridges within the region. The rate of K recommended at different K soil test levels is shown in Table 10.

Potassium fertilizer may be broadcast or banded. Banded K should not be placed with the seed. At least 1 inch of separation between seed and fertilizer is required.

Nitrogen and Inoculation

Many legumes have the ability to fix N from the air without the use of commercial fertilizers if inoculated with N-fixing bacteria. The N-fixing bacteria for dry bean is called Rhizobium phaseolus, and it is specific for dry beans. Inoculants used for soybeans or peas are different and will not infect dry bean roots.

Unfortunately, the relationship between dry bean and Rhizobium phaseolus is not strong. Dry, hot weather, short periods of soil water saturation and cold weather all will result in sloughing off of nodules, so achieving high dry bean yields consistently using inoculation for an N source may be difficult.

In the last 20 years, researchers in North Dakota and Minnesota have conducted more than 30 site-years of N-rate trials on dry beans. Using an N cost of 30 cents per pound of N and a dry bean price of 20 cents per pound, the return to N in inoculated trials was mostly negative for N rates in excess of 40 pounds/acre.

From these data, inoculated trials did not benefit from N rates greater than 40 pounds/acre, including trials where yields increased up to 100 pounds of N/acre. Fertilization at rates more than 70 pounds/acre provided little economic advantage. Risks of later maturity, and increased incidence and severity of white mold disease would favor 70 pounds/acre rates vs. higher N rates.

The most economical N rate was not related to yield potential. Therefore, no scale of yield potential is made in dryland dry bean N recommendations for maximum economic production. In years when environmental conditions favored higher yields, the conditions also favored increased organic matter mineralization and more efficient uptake of N by the dry beans.

N recommendations for dryland dry edible beans:

Inoculated: 40 pounds/acre less STN (soil test N) to a depth of 2 feet
Non-inoculated- 70 pounds/acre less STN

Irrigated Production

Most irrigation is sited on well-drained, coarser-textured soils. Inoculation has not been found adequate for supporting higher yields of dry beans produced under irrigation.

Therefore, supplemental N is very important to achieve the high yield potential in irrigated fields. Not only is supplemental N encouraged, but split applications of N are also encouraged to increase N efficiency and prevent N leaching.

The formula for N recommendations under irrigation is:

N rec = YP X 0.05 – STN-PCC

Where YP is the yield potential based on past history of the grower or field.
STN is the soil test N acquired in fall or spring to a depth of 2 feet.
PCC is the previous crop credit from a previous legume, sugarbeet tops or another N source such as a cover crop.

A small preplant application of N is advised, usually less than 40 pounds of N/acre. The first supplemental N application can be a side-dressed ammonia, UAN or urea application before vining. Subsequent applications can be made through the irrigation system and completed before top pod fill begins.

Zinc

Dry bean is one of only a few crops in the region to respond regularly to Zn fertilizer in low-zinc soils. Soils with soil test levels below 0.8 parts per million (ppm) may respond to fertilizer zinc application.

Zinc deficiency may be seen as bronzing, browning and death of leaf tissue, stunting and poor vining. Zinc deficiency may be treated by foliar sprays of zinc sulfate, zinc chelate or ammoniated zinc solutions. Zinc deficiency may be prevented with preplant or planter treatments of zinc sulfate, zinc chelates or ammoniated zinc solutions.

A treatment of 3 to 5 pounds/acre of actual Zn preplant incorporated as zinc sulfate may improve soil Zn availability for several years. Studies have shown that greater water solubility of the Zn source is important for Zn utilization by plants.

A liquid starter such as a zinc chelate or ammoniated zinc complex can be applied. Product rates as low as 1 pint/acre have shown effectiveness.

Most grower rates range from 1 to 1.5 quarts/acre. Zinc diluted with water and applied with the seed is preferred versus mixing with another liquid fertilizer, in order to minimize stand loss

If the starter band is separated from the seed by at least an inch, the liquid Zn fertilizer may be applied with the liquid starter fertilizer, provided that a jar test shows that they are compatible when mixed together.

Iron Chlorosis

Dry beans generally are more resistant to iron deficiency chlorosis (IDC) than soybean, but it still can be seen in some fields under certain conditions. Iron chlorosis appears as interveinal yellowing of upper leaves in response to low available soil iron due to high levels of carbonate minerals with or without high levels of soluble salts.

Soil pH levels higher than 7 may be accompanied by high levels of calcium/magnesium carbonates in the soil. Carbonates dissociate in moist soils to form bicarbonate, which lowers the dry bean plant’s ability to take up soil iron. Wetter soils contain higher levels of soluble bicarbonate than dry soils.

Wetter soils also may contain higher levels of salts due to shallower soil water tables. The combination of high levels of soil carbonates and salts has been shown to increase the level of iron chlorosis symptoms in soybean.

A similar relationship also is likely for dry beans. Iron chlorosis may be minimized by planting cultivars showing tolerance and having a higher tolerance to salt. Iron sprays have performed inconsistently in the past but if used, they should be applied early in the season for best results. Late-season spraying after about the third trifoliolate leaf would reduce effectiveness.

Iron sprays of ferrous sulfate or iron chelates have been used with limited success. Application of iron amendments with postemergence herbicides is not recommended.

If a field has shown a history of IDC in dry beans, avoid the field entirely or grow an IDC-tolerant cultivar and maybe plan to in-furrow apply an ortho-ortho-EDDHA iron chelate (for example, Soygreen) to help iron nutrition.

Salts

Dry beans are very sensitive to salt damage. Levels of salt (EC, electrical conductivity) higher than 0.5 millimho per centimeter (mmho/cm) as a 1:1 soil water extract begin to reduce yield. Salt levels are reduced by lowering water table levels. This is difficult to do in exceptionally wet years.

Soil salts can be reduced through tile drainage, but in many areas of eastern North Dakota, the effect of sodium within inclusions in the field may be enhanced and certain areas rendered unproductive. In the absence of tile drainage, lower salt levels are achieved by continuously cropping and introducing deep-rooting crops into the rotation.

The use of cover crops before or after seeding in the rotation, or a roadside buffer of alfalfa strips also may be helpful. See the NDSU Extension publication “Managing Saline Soils in North Dakota” (SF1087) for more information.

Weed Control

The weed control suggestions in this production guide are based on the assumption that all herbicides mentioned will have a registered label with the Environmental Protection Agency. Herbicides that no longer are registered or have not received registration for dry edible bean should not be used.

Dry beans treated with a nonregistered herbicide may have an illegal residue that, if detected, could cause condemnation of the crop. Nonregistered herbicide use is illegal, and a user could be subject to a heavy fine even without detectable residue.

Navy beans generally are less tolerant to herbicides than other dry bean classes or soybean. A rotary hoe used before or soon after weed emergence and before crook stage or after emergence up to first trifoliolate leaf stage may supplement weed control with herbicides.

Eptam (EPTC) plus Prowl, Sonalan or Treflan (or generic equivalent) controls many grass and broadleaf weeds. Incorporate 4 to 6 inches deep immediately after application.

Dual (S/metolachlor), Outlook (dimethenamid) {or generic equivalents of these products} applied PPI (preplant incorporated) or PRE (pre-emergence) controls annual grasses and some broadleaf weeds. PPI may provide more consistent weed control because PRE requires rainfall for activation.

Outlook can be applied in sequential treatments for improved nightshade control. Outlook PPI or PRE provides greater nightshade control than Dual but may degrade in soil before nightshade emergence ceases. Apply Outlook EPOST (early postemergence) up to third trifoliolate dry beans to reduce late nightshade emergence.

Pursuit (imazethapyr) applied PPI, PRE or POST controls many broadleaf weeds. Pursuit can be applied only PPI within one week of planting or PRE up to three days following planting. Do not apply POST (postemergence) to ‘Domino’ black bean. Do not apply after crop begins to flower or when cold and/or wet weather are present or predicted to occur within one week of application.

Do not use oil additives or liquid fertilizer. Apply with NIS (nonionic surfactant) at 0.25% v/v to dry beans with at least one trifoliolate leaf. Refer to label for additional information on application use and restrictions, including crop rotation restrictions. User assumes all risk of liability for injury.

Reflex (fomesafen) applied POST with NIS at 0.25 to 0.5% v/v or oil adjuvant at 0.5 to 1% v/v controls many broadleaf weeds. Oil adjuvant may increase weed control but also increases the risk of dry bean injury.

NDSU research has shown good to excellent kochia control when applied at high spray volumes (greater than 17 gpa), with oil adjuvants (especially MSO type), at labeled rates, and to kochia less than 2 inches tall.

Basagran (bentazon) at 0.5 to 1 qt/A applied POST controls many annual broadleaf weeds and suppresses Canada thistle. NDSU research has shown greater broadleaf weed control, especially for kochia, lambs¬quarters, redroot pigweed and wild buckwheat, by applying Basagran as split treatments twice each at 1 pt/A, three times each at 0.67 pt/A or four times each at 0.5 pt/A, compared with one application at 2 pt/A.

Make applications seven to 10 days apart, depending on the weed growth rate, growing conditions, size of weeds at application, degree of weed control from first application and sequential flushes. The first application must be made to small weeds (1 inch).

For Canada thistle suppression, apply Basagran at 1 qt/A when plants are 8 inches tall to bud stage. Make a second application at 1 qt/A seven to 10 days later.

Sequential micro-rate applications will provide greater broadleaf weed control than from a single application at full rates and can be used in all crops where Basagran is labeled. Apply with an oil additive at 1 qt/A (1 pt/A by air). Do not reduce the amount of oil adjuvant with the micro-rate.

MSO (methylated seed oil) adjuvant has shown greater enhancement of Basagran than petroleum oil (COC) adjuvants (Table 12). Basagran is safe for dry beans at all stages.

The total maximum seasonal use rate is 4 pt/A, so the micro-rate can be increased if weeds are large at application or if sequential applications are delayed due to rain or wind.

Basagran commonly is combined with fertilizer micronutrients that may cause incompatibility problems resulting in zinc precipitation. Chelated zinc materials have greater incompatibility problems than unchelated material. Recommendations to prevent precipitation are to fill the sprayer with water, add Basagran and thoroughly agitate, then add zinc fertilizer material.

The NDSU dry bean micro-rate concept is based on the sugarbeet micro-rate and substitutes additional weed management for reduced herbicide rates. Application to small weeds is essential for success.

The micro-rate can be applied more than once in dry beans to control emerging weed flushes, but applying a foundation herbicide treatment (DNA [Group 3] or acetanilide [Group 15]) may require only one POST application. MSO adjuvant is required for optimum weed control. The POST grass herbicide can be excluded if grass populations are low.

Weed control from the micro-rate is best when the temperature plus humidity is greater than 140. Increasing spray volume and using AMS may help improve weed control when the value is below 140. Research also has shown control of wild mustard, nightshade, buckwheat, ragweed and cocklebur from the micro-rate.

Herbicide Carryover

Besides carryover potential there are also grazing restrictions for certain herbicides used in dry beans (Table 13).

The persistence of phytotoxic levels of an herbicide for more than one year can be a problem with some of the herbicides used in North Dakota. Herbicide residues are most likely to occur following years with unusually low rainfall because the chemical and microbial activity needed to degrade herbicides is limited in dry soil.

Crop damage from herbicide residues can be minimized by applying the lowest herbicide rates required for good weed control, using band rather than broadcast applications and mold-board plowing before planting the next crop.

Mold-board plowing reduces the phytotoxicity of some herbicides by diluting the herbicide residue in a large volume of soil. Mold-board plowing is effective in reducing the residual effects of trifluralin, Sonalan, Prowl, Nortron SC, atrazine and metribuzin.

Rotation restrictions for planting dry beans after use of herbicides are provided in Table 14.

Relative Herbicide Effectiveness on Weeds

The ratings in Table 15 show relative herbicide effectiveness at labeled rates. Under favorable conditions, control may be greater than indicated, and under unfavorable conditions, herbicides may give erratic results. Dry and cool weather increases herbicide persistence, while wet and/or warm weather reduces herbicide persistence.

Reference