Title

Soybean Production Field Guide for North Dakota

(A1172, Revised Apr. 2019)
File
Summary

The North Dakota Soybean production field guide provide producers with data fo soybean production information throughout the state. It addresses issues from variety selection, growth and fertilizing, disease, insect and weed control, harvesting and storing of soybeans.

Lead Author
Lead Author:
Edited and compiled by Hans Kandel and Greg Endres, NDSU Extension Agronomists
Availability
Availability:
Available in print
Publication Sections

Introduction

Changing weather conditions with varied rainfall amounts and stored soil water require soybean [Glycine max (L.) Merr.] growers to make careful decisions regarding tillage system, fertility management, variety selection, seedbed preparation, weed control strategies, crop rotations, water management and pest management practices.

This field guide has been developed to help you make timely management decisions. However, detailed and extensive information on any one area is not provided because of limited space. Complete discussions of soil fertility; weed, disease and insect control; variety performance; harvesting; and storage are available in other Extension publications as listed in the back pages.

The pesticide use suggestions in this guide are based on federal label clearances and on some state labels in North Dakota. Also, suggestions are based on research information collected in North Dakota State University experiments or trials in other states. All pesticides listed had a federal or state label at the time of publication of this guide. Check all pesticide labels at the time of use for the most current label registration.

Modern technology, fluctuating export markets, changing U.S. Department of Agriculture farm policies and environmental regulations all contribute to soybean growers’ needs for careful planning and management to assure high yields and profitable production.

The publishers and contributors do not assume any responsibility, make any guarantees or offer any warranties in regard to the results obtained from the use of the recommendations appearing in this guide.

Soybean Growth and Development

The soybean is a dicotyledonous plant that has epigeal emergence, meaning that during germination, the cotyledons are pulled through the soil surface by an elongating hypocotyl. The soil-penetrating structure is the hypocotyl arch.

Once emerged (VE stage), the green cotyledons (seed halves) open and supply the new seedling with stored energy while capturing a small amount of light energy. The growing point is between the two cotyledons, and because it is above the ground, it could be killed by a spring frost or physical damage. This is in contrast with corn, wheat, field pea or lentil, in which the growing point is below the surface during the early development stages.

The first true vegetative leaves formed are the unifoliolate leaves. These two single leaves form directly opposite one another above the cotyledonary node (VC stage). All other leaves are trifoliolates and consist of three leaflets (V1-n stages) and have an alternate arrangement on the stem.

Growth Stages

Soybean development is characterized by two distinct growth phases. The first is the vegetative (V) stages that cover growth from emergence to flowering. The reproductive (R) stages cover growth from flowering through maturation.

Diagram showing the parts of a soybean plant in the vegetative stages.
Figure 1. Soybean emergence.

Plant stages are determined by classifying leaf, flower, pod and seed development. Staging also requires node identification. A node is the part of the stem where a leaf is (or has been) attached. 

A diagram of the parts of the soybean plant in the reproductive stages of development.
Figure 2. The soybean plant in V2 stage of development.

 

Vegetative Stages (V)
Stage Description
VE Emergence – Cotyledons above the soil surface
VC Cotyledon – Unifoliolate leaves unrolled sufficiently so that the leaf edges are not touching
V1 First-node – Fully developed leaves at unifoliolate node
V(n) nth-node – The “n” represents the number of nodes on the main stem with fully developed leaves beginning with the unifoliolate leaves

From Fehr, W.R., and C.E. Caviness. 1977. Stages of soybean development. Spec. Rep. 80. Iowa State Univ. Coop. Ext. Serv., Ames.

Reproductive stages (R)
Stage Description
R1 Beginning bloom – One open flower at any node on the main stem
R2 Full bloom – Open flower at one of the two uppermost nodes on the main stem with a fully developed leaf
R3 Beginning pod – Pod 3/16 inch long at one of the four uppermost nodes on the main stem with a fully developed leaf
R4 Full pod – Pod 3/4 inch long at one of the four uppermost nodes on the main stem with a fully developed leaf
R5 Beginning seed – Seed 1/8 inch long in a pod at one of the four uppermost nodes on the main stem with a fully developed leaf
R6 Full seed – Pod containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem with a fully developed leaf
R7 Beginning maturity – One normal pod on the main stem that has reached its mature pod color
R8 Full maturity – Ninety-five percent of the pods have reached their mature pod color. Five to 10 days of drying weather are required after R8 for the soybean moisture levels to be reduced to less than 15 percent.

From Fehr, W.R., and C.E. Caviness. 1977. Stages of soybean development. Spec. Rep. 80. Iowa State Univ. Coop. Ext. Serv., Ames.

Number of days between stages.
Stages Avg. days (Fehr) Range in days (Fehr)
Planting to VE 10 5-15
VE to VC 5 3-10
VC to V1 5 3-10
V1 to V2 5 3-10
V2 to V3 5 3-10
V3 to V4 5 3-8
V4 to V5 5 3-8
beyond V5 3 2-5
R1 to R2 3 0-7
R2 to R3 10 5-15
R3 to R4 9 5-15
R4 to R5 9 4-26
R5 to R6 15 11-20
R6 to R7 18 9-30
R7 to R8 9 7-18

From Fehr, W.R., and C.E. Caviness. 1977. Stages of soybean development. Spec. Rep. 80. Iowa State Univ. Coop. Ext. Serv., Ames.

Number of days between stages (0.0-0.5 relative maturity).
Stages Avg. days (Carrington) Range in days (Carrington)
Planting to VE 18 11-26
VE to V1 13 11-15
V1 to V3 10 8-12
V3-R1 13 8-16
R1 to R3 16 12-20
R3 to R5 11 6-14
R5 to R7 36 32-44
R7 to R8 6 5-10

From Endres et al. Carrington Research Extension Center Annual Reports.

Extremes in growing conditions, such as temperature, rainfall and soils, can alter the development of soybean greatly. Many post-applied herbicides are labeled for application at certain soybean growth stages. To avoid herbicide injury (some herbicides), we highly recommend you identify development by growth stage and not use plant height, planting dates or row closure as a basis for application timing.

Variety Selection and Adaptation

Soybean variety selection should be based on maturity, yield, seed quality, lodging resistance, iron-deficiency chlorosis tolerance and disease reaction. Comparative maturity and yield of public and private soybean varieties can be obtained from a current copy of Extension publication A843, “North Dakota Soybean Variety Trial Results and Selection Guide.”

Later-maturing varieties tend to yield more than early maturing varieties when evaluated at the same location. After determining a suitable maturity for the field, comparing yields of varieties that are of similar maturity is important. Although late maturity increases yield potential, later-maturing varieties have more risk than earlier-maturing varieties because an early fall frost may kill a late-maturing variety before the beans have completely filled in the pods, which impacts yield and quality.

Soybean Maturity

Soybean respond to day length (the increase of the night length) and heat units, so the actual calendar date a variety will mature is highly influenced by latitude; each variety has a narrow range of north-to-south adaptation. A model is available at the North Dakota Agricultural Weather Network. It will predict the soybean maturity based on the selected maturity group, planting date and nearest weather station.

Soybean yield and quality are affected if a season-ending freeze occurs before a variety reaches physiological maturity. Dates of maturity are listed in the annual NDSU performance tables and indicate when varieties were physiologically mature. Usually harvest can commence approximately seven to 14 days after the soybean crop is physiologically mature.

Relative maturity ratings are provided for many of the varieties entered in the trials at various locations. Relative maturity ratings for private varieties were provided by the companies entering the variety in the trial.

Varieties of maturity groups 00 (double zero), 0 (zero) and 1 are suitable for eastern North Dakota. Maturity group 00 is very early and primarily is grown in the northern Red River Valley and the north-central area of North Dakota. Maturity group 0 is adapted to most North Dakota counties, while maturity group 1 primarily is suitable for southeastern North Dakota. These maturity groups are further subdivided. For example, a 0.1 maturity group is an early group 0 variety and a 0.9 is a late-maturity group 0 variety.

The best way to select a high-yielding variety is to use data averaged across several locations and years. Because weather conditions are unknown in advance, averaging across several years’ data will identify a variety that likely will yield well across different weather conditions. Selecting a variety that has performed relatively well in dry and moist conditions is the best way to identify a variety that does well, regardless of weather fluctuations.

Phytophthora

Phytophthora root rot caused by the soilborne-fungus Phytophthora sojae is a major disease of soybean in North Dakota. Phytophthora root rot tends to be more of a problem in the Red River Valley (RRV) and on poorly drained, heavy-textured soils, but the disease can cause significant stand reduction and yield loss in other areas when conditions are favorable.

Many varieties have Phytophthora root rot-resistance genes. Each gene for resistance confers resistance to a different race (or races) of Phytophthora. For example, a gene that may confer resistance to Race 3 may not confer resistance to Race 4, and vice versa.

According to a survey of Phytophthora races done by NDSU’s soybean pathologist, Berlin Nelson, Races 3 and 4 are the most common in North Dakota. However, numerous other races are found, especially in the RRV.

The two most common resistance genes found in commercial soybean varieties are Rps 1c and Rps 1k. Unfortunately, numerous races can attack those sources of resistance.

Two better sources of resistance are Rps 3A and Rps 6, and varieties that have two different genes for resistance also are a good choice. Although the use of a soybean variety with resistance to P. sojae does not guarantee control because you will not know what races of P. sojae are in your fields, deploying resistance genes will maximize the likelihood of some protection against Phytophthora root rot.

Iron-deficiency Chlorosis

Iron-deficiency chlorosis (IDC) is a major problem primarily in the eastern part of North Dakota and is caused by iron being less available in soil with a pH greater than 7 and the presence of soil carbonates. Iron-chlorosis symptoms are most common during the two- to seven-trifoliolate leaf stages.

Plants tend to recover and start to turn green again during the flowering and pod-filling stages. However, IDC during the early vegetative stages can reduce yield severely.

Some varieties are more tolerant to IDC than others. For high-pH soils with known IDC problems, select an IDC-tolerant variety of suitable maturity that is high yielding. Data on genetic differences for IDC tolerance is available in publication A-843, “North Dakota Soybean Variety Trial Results and Selection Guide.”

Soybean Cyst Nematode

The soybean cyst nematode (SCN), Heterodera glycines, is a small parasitic roundworm that attacks the roots of soybean plants. Nematodes often are undetected because above-ground symptoms are uncommon until a 15 to 30 percent yield loss has occurred.

Soybean cyst nematode has been confirmed in 19 counties in North Dakota as of 2019. Growers are strongly urged to test their soils for SCN. If a positive sample for SCN is found, growers should begin managing SCN actively.

Crop rotation and resistance are the most important management tools against this disease. Two sources of resistance to SCN — PI88788 and Peking — can be found in varieties suitable for North Dakota. These sources are effective in the vast majority of the soybean fields in the state. However, the level of resistance in each variety is variable, so selecting the most resistant variety possible and monitoring the field for SCN is important.

For SCN management, a rotation out of soybean for two to three years is beneficial. Dry edible beans are susceptible to SCN and should not be used as a rotation crop for managing SCN. Nematicide seed treatments also are available and may help manage SCN; however, they are not a substitute for resistance and rotation.

Specialty Soybean

Food Soybean

Some soybean varieties have been developed for human consumption and have special food-processing characteristics. Tofu is a white curd that primarily is consumed in Asian countries. Special varieties have been developed that are high in protein and make smooth-textured tofu. These high-protein tofu types are lower yielding than the regular varieties that are sold to the elevator.

Natto is another human food product made from soybean. Natto is a fermented product made from whole soybean that is cooked. Natto varieties are very small seeded and tend to yield even less than the specialty varieties developed for the tofu market.

Growers should consult university publications on soybean variety performance to determine how much less these specialty varieties yield, compared with oilseed soybean. Based on the lower yield, a higher price per bushel needs to be obtained to economically justify growing these specialty soybean types. A contract should be arranged prior to growing these special types so that a market will be available.

Oil Modified

Soybean varieties with modified oil content are commercially available. Different fatty acid compositions modify the type of oil the soybean plant produces in the seed. Low saturated fats are desirable because this type of oil is better for human health.

High oleic, low palmitic, low stearic and low linolenic acid content are all genetic modifications that produce more healthful oil for human consumption. We have seen no indication that these modifications reduce yield.

However, yield of specific varieties with modified oil content should be evaluated to determine whether high yield has been incorporated with the modified oil content. These specialty varieties should be marketed as identity-preserved (IP).

Seedbed Preparation

Soybean can be grown on a wide range of soil types under various cultural practices. Because of seed size and physiology, soybean seeds require about 50 percent of the seed weight in moisture to germinate. Also, soybean is planted only 1 to 1½ inches deep. These factors explain why preparation of a firm, uniform seedbed is important for optimum stand establishment.

Many farmers are growing soybean using conservation tillage including no-till. Special planters or drills may be required to handle surface residue in no-till and some reduced-tillage systems.

Soybean, like other legume crops, has difficulty emerging through compacted layers and surface crusts. Soybean is very susceptible to elevated salt levels in the soil and waterlogged conditions.

Planting Date

Soybean is susceptible to frost and prolonged exposure to near-freezing conditions in the spring and fall. Plant soybean after the soil has warmed to 50 F and air temperatures are favorable.

Soybean generally should not be planted earlier than five days before the average last killing frost or projected last frost date for a season. This provides less than a 50 percent chance of frost killing the soybean plant. Early in the season in a no-till or minimum-till situation, the residue tends to retard heat transfer from the soil to the air, which creates a potential for more frost damage to the young soybean plant.

Very early planting in cool, wet soil may result in low germination, increased incidence of seedling diseases and poor stands. Planting dates during the first half of May are favorable for highest yields with a reduced risk of frost injury.

Planting early in the season allows the use of full-season varieties, which typically yield more than shorter-season varieties. Recent research indicates that if conditions are right during the planting season, waiting to plant may reduce the yield by 0.3 bushel per acre per day delay.

Data from NDSU date-of-planting studies indicated that late plantings had lower seed yields, poorer seed quality, lower oil content, shorter plant height and pods set closer to the ground, compared with optimum planting dates. Yield increased 8 percent with first week of May or earlier planting dates when averaged across nine NDSU trials conducted in south- and east-central North Dakota.

Some early maturing varieties have had acceptable yields when weather factors such as hail, late spring frost, or floods necessitate late planting or replanting.

Soybean stands with poor emergence often are replanted without considering the yield-compensating ability of the plants in the initial stand. The yield of an initial planting at less than full stand must be compared to the yield of the replanted crop to determine whether replanting is justified.

Replanting costs include seed, tillage, replanting and labor. The yield of a replanted crop must be sufficiently greater than the yield of the initial planting to cover the expenses associated with replanting. The risk of fall freeze damage to the replanted crop must be considered when deciding the maturity of the variety selected for replanting.

Planting Rate and Depth

Soybean yields have not varied significantly for a wide range of plant populations. An established plant population of approximately 150,000 plants per acre is desirable regardless of row spacing. Averaged across 44 NDSU trials, planting rates of 150,000 to 175,000 pure live seeds (PLS) per acre increased yield by 6 percent, compared with planting rates of 100,000 to 130,000 PLS/acre.

Seeds per pound in available varieties range from 2,200 to 3,400, with an average of 3,000 seeds per pound. High planting rates may cause yields to decrease in low-rainfall environments because of drought stress, and in a good rainfall year, high planting populations may lodge more than low populations. Low plant populations reduce lodging but contribute to low pod set and excessive branching.

An extremely low seed number per foot of row may result in erratic stands due to a lack of seedling energy necessary to break the soil surface. This may be critical in solid-seeded stands in which soils are prone to crusting.

Planting rates should be increased (around 10 percent) to compensate for naturally occurring factors that cause some live seeds not to become established plants. Slightly higher planting rates also may be advantageous with late planting dates or in no-till, where soil temperatures generally are lower.

If planting in narrow row spacings (less than 10 inches), we suggest that soybean planting rates be adjusted upward. Planting rates of 175,000 seeds per acre in 12- to 15- inch row spacings and 200,000 seeds per acre when drill seeding are recommended.

To ensure planting enough soybean seed, the planting rate should be based on a seed count. You will need to know the following to calculate the rate:

  1. Desired established plant population
  2. Average stand loss for your farm
  3. Germination value of your seed
  4. Number of seeds per pound of seed

The following is an example for calculating planting rate

  1. Desired established plant population is 150,000 plants per acre
  2. Normal stand loss is 10 percent
  3. Seed germination is 95 percent
  4. Soybean seed has a seed count of 3,000 seeds per pound, or 180,000 seeds per bushel

The planting rate (PR), expressed as the number of seeds per acre can be calculated from the following equation: PR = D*[100/(M1)]*[100/(100-M2)], where D is the desired plant density per acre 150,000, M1 (germination percent = 95 percent) and M2 (average percent stand loss on the farm = 10 percent).

PR = 150,000*[100/(95)]*[100/(100-10)] = 175,450 seeds per acre

175,450 seeds ÷ 3,000 seeds per pound = 58.5 pounds/acre (lb/a) of soybean seed needs to be planted.

Plan to cover seed 1 to 1½ inches deep and place the seed in moist soil. Planting deeper than 2 inches or in a soil that crusts may result in poor emergence and plant stand.

Row Spacing

Midwest research demonstrates that higher yields of soybean can be obtained in rows less than 30-inch spacing if stands are well-established and weeds are controlled adequately. NDSU research indicates that 14- to 22-inch row soybean outyield wider-spaced (28- to 30-inch) soybean by an average of 4 percent when averaged across 24 trials.

The advantages of narrow-row soybean are increased yield, reduced soil erosion, increased harvesting efficiency, and early crop canopy closure to help conserve soil moisture and suppress weeds. Planting in wider rows provides the opportunity to use row-crop planters, permits cultivation for weed control and may reduce the risk of white mold (sclerotinia).

Planting Guide

To determine the number of seeds per acre planted, add seed to your planter or drill and operate it on a firm soil surface so seed is visible on the surface. Operate it for a short distance close to your normal operating speed. Then go back and count the number of seeds dropped in 1 linear foot of planter row.

Make several counts and determine an average. Refer to one of the following charts to see that you are planting the number of seeds that you calculated in the earlier section.

Soybean seeds per linear foot of row (seed count of 2,500 seeds per pound).
Approx. lbs. live seed/acre Seeds/acre 6 in. rows 12 in. rows 22 in. rows 30 in. rows
40 100,000 1.2 2.3 4.2 5.7
50 125,000 1.4 2.7 5.3 7.2
60 150,000 1.7 3.4 6.3 8.6
70 175,000 2.0 4.0 7.4 10.0
80 200,000 2.3 4.6 8.4 11.5

 

Soybean seeds per linear foot of row (seed count of 3,000 seeds per pound).

Approx. lbs. live seed/acre Seeds/acre 6 in. rows 12 in. rows 22 in. rows 30 in. rows
40 120,000 1.4 2.8 5.0 6.9
50 150,000 1.7 3.5 6.3 8.7
60 180,000 2.1 4.2 7.5 10.4
70 210,000 2.5 4.9 8.8 12.1
80 240,000 2.8 5.6 10.0 13.8

Air Seeder Calibration

Calibrating an air seeder usually is done by following the directions listed in the operators manual. It usually will tell you to hand turn the seed metering system a number of turns for a predetermined area. This often is listed for 1/10 or ¼ acre.

Then the metered seed needs to be weighed on a scale. Sometimes these scales are provided with the air seeder. The weights need to be multiplied by 10 for 1/10 acre or multiplied by 4 for ¼ acre, and then adjustments can be made based on the previous calculated amounts.

Another method for calibrating an air seeder requires collecting seed from the seed openers. Probably the easiest method is to place a tarp under the openers, collect seed over an area or distance (1/10 acre) and weigh the pounds of seed collected.

  1. First, determine the pounds of seed to plant as calculated in the planting rate section of this publication. Then (1) determine the circumference (ft.) of the seed meter drive wheel on your seeder using the following formula:
    c(ft) = diameter in inches x 3.14/12 inches per foot
  2. Determine the drive wheel revolutions required to equal 1/10 acre. Use the following chart to calculate this number, which is based on the width of your air seeder.
    Travel distance to equal 1/10 acre.
    Drill width (ft.) Distance (ft.)
    16 272
    20 218
    24 181
    28 156
    32 136
    36 121
    40 109
    44 99
    48 91
  3. Next, calculate the metering wheel revolutions to cover this distance:
    Metering wheel revolutions = distance to cover one-tenth acre (ft.)/Circumference of drive wheel (ft.)
  4. Place seed in the air seeder bin and start the air delivery system. Manually turn the metering wheel the number of revolutions that were calculated to cover 1/10 acre.
  5. Weigh the seed collected on the tarp and multiply times 10. This number should equal the pounds of seed you want to plant.

Drill calibration is becoming extremely important so you can be sure you are planting the correct amount of seed. If the amount of seed determined with either method is not equal to the amount of seed you desire, make an adjustment to the feed rate and recheck your seeder. This method also works for determining the pounds of fertilizer to be applied.

Hula Hoop Method for Determining Population of Drilled Soybean1.
No. of plants 302 322 342 362 382
10 89,000/a 78,000/a 69,000/a 62,000/a 55,000/a
12 107,000/a 94,000/a 83,000/a 74,000/a 66,000/a
14 124,000/a 109,000/a 97,000/a 86,000/a 77,000/a
16 142,000/a 125,000/a 110,000/a 99,000/a 89,000/a
18 160,000/a 140,000/a 124,000/a 111,000/a 100,000/a
20 178,000/a 156,000/a 138,000/a 123,000/a 111,000/a
22 196,000/a 172,000/a 152,000/a 136,000/a 122,000/a
24 213,000/a 187,000/a 166,000/a 148,000/a 133,000/a
26 231,000/a 203,000/a 179,000/a 160,000/a 144,000/a
28 249,000/a 218,000/a 193,000/a 173,000/a 155,000/a
30 266,000/a 234,000/a 207,000/a 185,000/a 166,000/a
32 284,000/a 250,000/a 221,000/a 197,000/a 177,000/a
34 302,000/a 265,000/a 235,000/a 209,000/a 188,000/a
36 - 281,000/a 249,000/a 222,000/a 199,000/a
38 - 297,000/a 362,000/a 234,000/a 210,000/a
40 - - 277,000/a 247,000/a 221,000/a
42 - - 290,000 259,000/a 232,000/a
44 - - 304,000/a 271,000/a 243,000/a
46 - - - 284,000/a 255,000/a

1Example: If you count 24 plants inside a 32-inch Hula Hoop, your plant population is 187,000 per acre. Make at least 10 random counts in representative areas per field.

2 Inside diameter of hula hoop in inches

Soybean Soil Fertility

Dave Franzen, Extension Soil Science Specialist

Soybean has a need for 14 mineral nutrients: nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), zinc (Zn), manganese (Mn), copper (Cu), iron (Fe), boron (B), chloride (Cl), nickel (Ni) and molybdenum (Mo). Of these, North Dakota soils provide adequate amounts to soybean except for N, P, K, S and Fe.

Nitrogen Fixation

Although the atmosphere is 78 percent nitrogen gas, plants cannot use it directly. Plants can use only ammonium-N or nitrate-N.

Soybean is a legume and normally should provide itself N through a symbiotic relationship with N-fixing bacteria of the species Bradyrhizobium japonicum. In this symbiotic relationship, carbohydrates and minerals are supplied to the bacteria by the plant, and the bacteria transform nitrogen gas from the atmosphere into ammonium-N for use by the plant.

The process of soybean infection by N-fixing bacteria and symbiotic N fixation is a complex process between the bacteria and the plant. The right species of N-fixing bacteria must be present in the soil, either through inoculation of the seed or the seed zone at planting.

N-fixing bacteria are attracted to soybean roots by chemical signals from the soybean root in the form of flavonoid compounds (1). Once in contact with the root hairs, a root compound binds the bacteria to the root hair cell wall. The bacteria releases a chemical that causes curling and cracking of the root hair, allowing the bacteria to invade the interior of the cells and begin to change the plant cell structure to form nodules.

The bacteria live in compartments, up to 10,000 in each nodule, called bacteroids (Figure 3). Each bacteroid is bathed in nutrients from the host plant, and the bacteroid takes nitrogen gas from the soil air and converts it to ammonium-N using the enzyme nitrogenase, which consists of one Fe-Mo (iron-molybdenum)-based protein and two Fe (iron)-based proteins. In this region, iron deficiency chlorosis (IDC) may result in poor nodulation and may contribute to N deficiency as well as iron deficiency.

Soybean nodule cross-section micrograph showing individual bacteroids.
Photo Credit:
Louisa Howard, Dartmouth College; used with permission
Figure 3. Soybean nodule cross-section micrograph showing individual bacteroids.

Using Inoculants

If soybean will be planted in a field for the first time, the seed will need to be inoculated with Bradyrhizobium japonicum (soybean inoculum). Several inoculum types can be used: peat-based, liquid-based or granular.

Of the three, granular appears to be the most foolproof for a first inoculation. The other two also can be used, but the frequency of mistakes is much higher. No formulation is free of error.

For the peat-based and liquid-based treatments, all seed should have inoculum attached to it when it enters the soil. Peat-based inoculants can vibrate off the seed if they are not applied with an adequate sticking agent. Application of liquids could be poorly calibrated and inoculum may not hit all the seed if the application is not made carefully. Even granular will have problems in performing if the seeder is poorly calibrated.

If you use proper care in handling and application, the success rate of all inoculation is very high. In the rare event that nodulation does not take place, supplemental N will have to be applied to reach yield potential. In-season foliar N application is not recommended, and slow-release liquid N sources have no higher foliar N efficiency, compared with UAN (urea-ammonium nitrate) solutions.

Frequency of soybean yield responses, grain yield and protein differences between experiments with or without a soybean history when seed is inoculated with Bradyrhizobium japonicum formulations at planting. (Carrington Research Extension Center, 2003-2007a and 2012a; NDSU Oakes Irrigation Research Site, 2007b).
Site year1 2003a 2004a 2005a 2007b 2007a 2012a
No. of treatments 38 23 25 7 11 6
Soybean history No Yes Yes Yes No Yes
No. of treatments higher than check 38 0 0 0 11 0
Yield without inoculation 32.8 29.1 39.6 55.9 46.1 56.1
Mean yield with inoculation 38.8 28.9 39.6 55.9 50.7 56.1
Grain protein of the check 31.5 33.5 33.5 35.1 32.0 34.6
Mean grain protein inoculated 35.0 34.5 (NS) 33.8 (NS) 35.1 34.1 34.6

1All site years Carrington except 2007b treatment study at Oakes.

If a field has been seeded to soybean previously and nodulation was effective, you have only a small chance that inoculating again will be economically effective (See table on page 27). Average across 16 NDSU trials, seed yield increased 2 percent with inoculated seed on fields with previous soybean production history, compared to non-inoculated seed.

In the region, soybean grown in soils with conditions that did not support iron deficiency chlorosis sometimes responded to higher soil nitrate levels. However, higher soil nitrate levels in soils increase the severity of IDC in soils where IDC supporting conditions prevail.

Nitrogen is not required by soybean if adequate inoculation is present. In North Dakota experiments, the only financial benefits to supplemental N have been to first-year soybean in which initial inoculation resulted in poor nodulation.

Nutrients

Nitrogen Recommendations for Soybean

Nitrogen is not recommended for soybean, even first-year soybean. Elevated soil nitrate may increase the likelihood and severity of iron-deficiency chlorosis. The economics of late-season N application do not justify application.

Phosphorus

Soybean respond better to broadcast applications of P than to banded applications with or near the seed. Several recent studies confirm that broadcast application of P is safer than in-furrow P and, therefore, more likely to provide the desired yield respond, compared with seed placement.

If soil test levels are low to very low (less than 8 parts per million [ppm]; Olsen P), then a separate application of broadcast P is justified. However, if soil test levels are medium or higher, the level of soybean’s response to P fertilizer is small, not justifying a separate P application. Soybean roots are excellent scavengers of P at medium or higher soil test levels.

Even though a broadcast application of P may result in several more bushels of soybean than a banded application, some producers will elect to apply P with the seed. No fertilizer of any kind is recommended with soybean seed in a 15-inch row or wider. However, using a double-disk drill with 6-inch spacings, up to 10 pounds of N per acre may be applied to soybean as a P fertilizer (do not use urea) without yield reduction. However, considering that the goal of any fertilizer application is to produce income, seed-banding research has shown limited economic success.

With air seeders, the risk to soybean plants with fertilizer spread across the seed zone will be decreased. Even though applying up to 10 pounds of N per acre with a 6-inch row spacing is possible, dry weather at planting will increase the risk of injury

Therefore, producers should not to push rates too hard toward the limit because of the variability within fields in sand and soil water content. Sandier textures and low available soil water soils may show more stand injury than other areas of the field. The best recommendation for P application is to broadcast it.

Potassium

Testing the soil for K and referring to the clay chemistry map of North Dakota for guidance in K fertilization are important. After many years of soybean production, some soils may have been mined of K.

Sandier textured soils in the beach ridges west or east of the Red River Valley have been low in K for many years. Some sandier hilltops in the glacial till plain or in residual materials west of the Missouri River also may be lower in K. Some limited soil testing based on general landscape will show whether K is needed in these areas.

Generally, coarser-textured soils are more at risk for K deficiency than heavier soils. However, with continuous soybean production, even heavy soils may be at risk of being deficient.

Potassium should be broadcast or banded, with the seed and fertilizer separated. Do not apply K fertilizers with the seed. If the soil test is less than 150 ppm in soils with a smectite/illite ratio greater than 3.5, application of 60 pounds per acre of K2O is recommended to prevent K deficiencies in a dry year. If the soil test is less than 120 ppm in soils with a smectite/illite ration less than 3.5, 60 pounds per acre K2O is recommended.

Phosphorus and potassium recommendation for soybean based on soil test.
Olsen Soil Test Phosphorus, ppm
VL 0-3 L 4-7 M 8-11 H 12-15 VH 16+
78 lbs/acre P2O5 52 lbs/acre P2O5 52 lbs/acre P2O5 0 lbs/acre P2O5 0 lbs/acre P2O5

 

Soil Test Potassium, ppm
VL 0-40 L 41-80 M 81-120 H 121-150 VH 150+
90 lbs/acre P2O5 90 lbs/acre P2O5 60 lbs/acre P2O5 30 lbs/acre P2O5 0 lbs/acre P2O5

 

Soil Test Potassium, ppm
Smectite/illite ratio (S/I) 0-120 120-150 >151
S/I > 3.5 lbs/acre K2O 60 lbs/acre K2O 60 lbs/acre K2O 0 lbs/acre K2O
S/I < 3.5 lbs/acre K2O 60 lbs/acre K2O 0 lbs/acre K2O 0 lbs/acre K2O

Sulfur

Sulfur deficiency has become common in corn and small grains in North Dakota, and canola is always at risk for S deficiency. Sulfur deficiency in soybean is rarer.

Soybean growing on sandy soils (loamy sands, sandy loams with low organic matter) are most at risk, particularly in a wet spring, but the overall risk even under these conditions still is low. Your most profitable option might be to observe soybean leaf color through the season and apply S to areas of the field that show S deficiency into the season.

Soil pH

Soybean plants grow best around a pH of 6.5. Lowering the pH from 8 to 6.5 is not an option because of the cost of amendments and the formation of salt if the application is successful. However, low pH values are common in fields in North Dakota.

Sampling by landscape position reveals pH patterns, whereas composite soil sampling does not. Application of ground limestone or sugar beet lime would be justified if the soil pH is lower than 6.

Zinc

Soybean is not sensitive to low soil Zn levels in North Dakota. Soybean grows well at Zn soil test values much lower than North Dakota Zn-sensitive crops, which are dry bean, corn, flax and potato.

Iron

North Dakota soils have about 5 percent of iron (Fe) by weight. However, only a tiny fraction ever is available to plants.

Iron in well water is reduced iron (Fe++ or Ferrous iron). Ferrous iron is very soluble in water. The weight of a No. 2 carpenter nail can be dissolved in water if it was ferrous iron.

Unfortunately, as soon as ferrous iron is exposed to oxygen, it oxidizes to oxidized Fe (Fe+++ or Ferric iron). Ferric iron is a trillion times less soluble than ferrous iron. Plants, except for aquatic plants such as rice and pondweed, implement Fe uptake strategies to improve Fe nutrition and avoid deficiency.

In soybean, Fe is mobile in the plant from germination through the first mono-foliolate leaf. As the first trifoliolate leaf emerges, Fe becomes immobile in the plant and must be taken up continually through the season to avoid deficiency.

The soybean strategy for Fe uptake begins by soybean roots acidifying the soil environment directly around the soybean root. The acid soil environment is necessary for the activity of an Fe-reducing protein that is secreted by the soybean root. If the root remains acidic, the Fe-reducing protein contacts oxidized iron and reduces it to soluble ferrous iron, making it available to the plant.

In soils that are susceptible to iron deficiency chlorosis, the causal soil condition is the presence of carbonates (CO3--). As the soil becomes wetter, the solubility of carbonates increases, producing bicarbonate (HCO3-). Bicarbonate neutralizes the acidity around plant roots and makes the Fe-reducing protein secreted by the roots ineffective.

Iron foliar sprays are generally not effective in correcting a deficiency. The best application to reduce IDC is ortho-ortho-EDDHA Fe chelate applied with water in-furrow at planting. The ortho-ortho-EDDHA not only succeeds in delivering Fe to the plant root early in the season, but after conveying its original Fe, it has the ability to go back into the soil solution, grab additional Fe and deliver it to the plant root with the soil water stream.

The amount of ortho-ortho EDDHA in relation to ortho-para EDDA (Figure 4) is very important. Recent research at NDSU has shown that the response of soybean to EDDHA fertilizer is directly proportional to the percentage of ortho-ortho EDDHA Fe.

Diagram of the amount of ortho-ortho EDDHA in relation to ortho-para EDDA
Figure 4. Ortho-ortho EDDHA (left); ortho-para EDDHA (right).

 

An effective IDC prevention strategy should not rely on the application of ortho-ortho-EDDHA alone, but on a comprehensive approach to the condition. An IDC-tolerant variety should be selected. A four-state study led by NDSU found that the highest yield for a soybean field with soils with and without susceptibility to soybean IDC would be best managed by planting a high-yielding, IDC-intolerant variety in non-IDC soils and an IDC tolerant-variety in the IDC-susceptible soils.

The main management factors in managing IDC are selecting a suitable field and a tolerant variety. However, if a tolerant variety is not enough to reduce IDC pressure, soybean could be planted in wide rows (30-inch) and/or at higher than normal planting rates. The causes of the increased plant density reducing IDC could be related to reduced soil moisture under the row, higher root-zone acidity that would favor activity of the Fe-reducing substance secreted by the soybean root, or other unidentified mechanisms.

A three-state study found that seeding a cover crop at 1 bushel per acre of oats or other easily killed small-grain cover crop about the day of soybean planting can reduce excess water and take up some excess soil N. Depending on soil moisture, the oats may be killed with herbicide early if conditions are dry, or up to the five-leaf stage of oats if the season is wet. The use of an oat cover crop resulted in as high as 40 bushels per acre more soybean where oats were used, compared with where they were not at a Minnesota site in a wet season.

Because soil salinity aggravates and increases the severity of IDC, a comprehensive, rotation-based strategy should be imposed to reduce soil salinity as much as possible. Management strategies include selection of better salinity-tolerant crops; the use of alfalfa strips to reduce roadside salinity; the use of alfalfa above saline seeps to reduce the severity of the seep; the use of cover crops when possible before, during or after cropping to reduce field water table; and possibly tile drainage if possible, practical and socially and/or regulation permissible.

Soybean yield as affected by preplant N rate and seeding an oat cover crop at eight Minnesota IDC sites. Lamb J., University of Minnesota.
N applied Oats C06 YM06 K07 YN07 C08 R08 C09 R09
0 lb.acre No 42.1 bu/a 52.0 bu/a 3.7 bu/a 51.7 bu/a 34.3 bu/a 30.4 bu/a 51.0 bu/a 42.0 bu/a
100 lb.acre No 28.6 bu/a 32.2 bu/a 0.3 bu/a 46.5 bu/a - - - -
200 lb.acre No 25.3 bu/a 19.1 bu/a 0.1 bu/a 40.2 bu/a - - - -
0 lb.acre Yes 42.5 bu/a 52.4 bu/a 40.2 bu/a 50.7 bu/a 41.7 bu/a 28.1 bu/a 50.0 bu/a 44.0 bu/a
100 lb.acre Yes 20.5 bu/a 42.6 bu/a 24.5 bu/a 43.4 bu/a - - - -
200 lb.acre Yes 18.9 bu/a 25.9 bu/a 7.2 bu/a 33.7 bu/a - - - -

 

Soybean Weed Control

Joseph Ikley, Extension Weed Specialist

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. Soybean treated with a nonregistered herbicide may have an illegal residue which, if detected, could cause condemnation of the crop.

Federal law makes liable for seizure any raw agricultural commodity that possesses a pesticide residue for which no exemption or tolerance has been established or that exceeds the tolerances established by the Food and Drug Administration. People using herbicides in a manner contrary to label instructions are subject to penalty under federal and state laws.

North Dakota State University or its officers or employees makes no claims or representations that the chemicals discussed will or will not result in residues on agricultural commodities and assumes no responsibility for results from using herbicides.

Instructions for the registered uses of herbicides are given on container labels. Read and follow label instructions carefully. Use pesticides only as labeled.

Herbicide labels also can be found on the web.

Soybean fall or spring early preplant herbicides
  Rate/A Before Planting
2,4-D amine1 0.5 lb ai 15 days
2,4-D amine1 1 lb ai 1 month
2,4-D ester1 0.5 lb ae 7 days
2,4-D ester1 1 lb ae 1 month
E-99 1 lb ae 15 days
Weedone 650 1 lb ae 15 days
Aim EC 2 fl oz 0
Affinity / thifensulfuron and tribenuron1
All formulations
Label rates 14 days
Banvel / dicamba1 4 fl oz 14 days
Banvel / dicamba1 1 pt 1.5 months
Elevore 1 fl oz 14 days
Express / tribenuron1
All formulations
Label rates 1.5 months
Harmony / thifensulfuron1
All formulations
Label rates 0
Liberty 280/generic1 29 to 36 fl oz 0
Gramoxone/generic1 - RUP Label rates 0
Pre-Pare 0.3 oz 9 months
Rage D-Tech 9 to 16 fl oz 7 days
Rage D-Tech 17 to 24 fl oz 14 days
Rage D-Tech 25 to 32 fl oz 1 month
Roundup/generic1 0.75 to 3 lb ae 0
Sequence 2.5 to 3.5 pt 0
Sharpen 1 to 2 fl oz 0-2 months
Spartan 3 to 8 fl oz 0
Spartan Advance 16 to 36 fl oz 0
Spartan Charge 3 to 8.5 fl oz 0
Valor2 2 to 3 oz 0

1or generic brand equivalent
2Valor = refer to label for rates >3 oz/A.

Soil-applied Herbicides in Soybean

Prowl
Prowl H2O

(pendimethalin)

Product/a (ai/a): 2.4 to 3.6 pt EC, 2.1 to 3 pt ACS, (1 to 1.5 lb)

Weeds: Annual grass and some broadleaf weeds.
When to Apply: PPI. Fall or spring.
Remarks and Paragraphs: Adjust rate for soil type. Do not apply PRE. Poor wild oat and no wild mustard control. Green foxtail has  become resistant to dinitroaniline (DNA) herbicides in North Dakota.


Sonalan
Sonalan 10G
(ethalfluralin)

Product/a (ai/a): 1.5 to 3 pt, 5.5 to 11.5 10G, (0.55 to 1.15 lb)

Weeds: Annual grass and some broadleaf weeds.
When to Apply: PPI. Fall or spring.
Remarks and Paragraphs: Adjust rate for soil type. Do not apply PRE. Poor wild oat and no wild mustard control. Green foxtail has  become resistant to dinitroaniline (DNA) herbicides in North Dakota.


Treflan/generic trifluralin

Product/a (ai/a): 1 to 2 pt, (0.5 to 1 lb)

Weeds: Annual grass and some broadleaf weeds.
When to Apply: PPI. Fall or spring.
Remarks and Paragraphs: Adjust rate for soil type. Do not apply PRE. Poor wild oat and no wild mustard control. Green foxtail has  become resistant to dinitroaniline (DNA) herbicides in North Dakota.


Sencor/generic metribuzin

Product/a (ai/a): Soil pH >7.5 = 0.25 lb DF; Soil pH <7.5 = 0.33 to 0.5 lb DF

 

Weeds: Broadleaf weeds including wild mustard.
When to Apply: PPI.
Remarks and Paragraphs: Sencor may injure certain soybean varieties.


Dual/S-metolachlor
generic metolachlor

Product/a (ai/a): 1 to 2 pt, (0.95 to 1.9 lb)

Weeds: Grass and some broadleaf weeds
When to Apply: PPI or PRE.
Remarks and Paragraphs: Dual may give greater weed control than generic metolachlor at equal product rates. Poor wild oat control  and wild mustard control. Shallow PPI gives more consistent control than PRE. PRE requires precipitation for herbicide activation. Adjust rate for soil type and OM. Outlook gives greater nightshade control.


Intrro/generic alachlor RUP

Product/a (ai/a): 2 to 3 pt, (2 to 3 lb)

Weeds: Grass and some broadleaf weeds
When to Apply: PPI or PRE.
Remarks and Paragraphs: Dual may give greater weed control than generic metolachlor at equal product rates. Poor wild oat control  and wild mustard control. Shallow PPI gives more consistent control than PRE. PRE requires precipitation for herbicide activation. Adjust rate for soil type and OM. Outlook gives greater nightshade control.


Outlook/generic Dimethenamid
Zidua SC

Product/a (ai/a): 16 to 21 fl oz (0.75 to 1 lb); 2.5 to 5.75 fl oz (0.08 to 0.19 lb)

Weeds: Grass and some broadleaf weeds
When to Apply: PPI, PRE or EPOST. PPI, PRE or EPOST.
Remarks and Paragraphs: Dual may give greater weed control than generic metolachlor at equal product rates. Poor wild oat control  and wild mustard control. Shallow PPI gives more consistent control than PRE. PRE requires precipitation for herbicide activation. Adjust rate for soil type and OM. Outlook gives greater nightshade control.


Valor
(flumioxazin)

Product/a (ai/a): 2 to 3 oz WDG (1 to 1.5 oz)

Weeds: Small-seeded broadleaf weeds, including pigweed, nightshade, kochia lambsquarters and B. wormwood.
When to Apply: EPP, Shallow PPI, and PRE.
Remarks and Paragraphs: PRE requires precipitation for herbicide activation. Refer to label for tank-mix options, application information and rate structure.


Spartan
(sulfentrazone)

Product/a (ai/a): 3 to 8 fl oz F (1.5 to 4 oz)

Weeds: Small-seeded broadleaf weeds, including pigweed, nightshade, kochia lambsquarters and B. wormwood.
When to Apply: EPP, Shallow PPI, and PRE.
Remarks and Paragraphs: PRE requires precipitation for herbicide activation. Refer to label for tank-mix options, application information and rate structure.


No aerial spraying
Python
(flumetsulam)

Product/a (ai/a): 0.8 to 1.33 oz DG or 5 to 3 a/pack (0.64 to 1.06 oz)

Weeds: Python does not control ALS- resistant kochia.
When to Apply: EPP, Shallow PPI, and PRE.
Remarks and Paragraphs: PRE requires precipitation for herbicide activation. Refer to label for tank-mix options, application information and rate structure.


Sharpen
(saflufenacil)

Product/a (ai/a): 1 fl oz (0.36 oz)

Weeds: Broadleaf weeds.​​​​​​​
When to Apply: EPP, Shallow PPI, and PRE.​​​​​​​
Remarks and Paragraphs: Sharpen has no grass activity. Provides burndown control of emerged broadleaf weeds. Planting interval is dependent on soil texture and OM. Refer to label for tank-mix options.

POST-Applied Herbicides in Soybean

Basagran/generic bentazon

Product/a (ai/a): 0.5 to 2 pt applied 1 to 4 times. (0.25 to 1 lb)

Weeds: Some broadleaf weeds.​​​​​​​
When to Apply: POST. Soybean: After emergence. Broadleaf weeds: Small.
Remarks and Paragraphs: Nonresidual, contact herbicide requiring thorough coverage. Most active in hot and sunny conditions. Add oil adjuvant at 1 to 2 pt/a. Allow a 30-day PHI.


Rezult +
MSO oil adjuvant

(bentazon & sethoxydim)

Product/a (ai/a): 1.6 + 1.6 pt or 0.8 + 0.8 pt 2X or 0.56 + 0.56 pt 3X or 0.4 + 0.4 pt 4X + 1.25 pt/a (1 + 1 lb or 0.5 + 0.5 lb or 0.38 +  0.38 lb or 0.25 + 0.25 lb)

Weeds: Small grass and broadleaf weeds, including pigweed, ragweed, kochia, lambsquarters, wild buckwheat, biennial wormwood and Canada thistle.​​​​​​​
When to Apply: First application: Weeds: 1 inch or less.
Remarks and Paragraphs: Make consecutive applications 7 to 10 days later. Weeds must be small at application. Refer to E3 for  additional information. MSO enhances weed control more than petroleum oil adjuvants. Sequential applications at 7- to 10-day intervals  improves overall weed control. Tank-mix with Raptor at 2 fl oz/A for improved weed control. Allow 30-day PHI.


Ultra Blazer
(acifluorfen)

Product/a (ai/a): 0.5 to 1.5 pt (0.125 to 0.375 lb)

Weeds: Small broadleaf weeds, including pigweed and common lambsquarters.​​​​​​​
When to Apply: POST. Soybean: 1 to 2 trifoliolates. Weeds: Small.
Remarks and Paragraphs: Contact, nonresidual herbicides requiring thorough coverage. Most active in hot and sunny conditions. 
May cause speckling on soybean leaves. Refer to label for crop response, adjuvant type and rate, and tank-mix options.


Cadet
(fluthiacet)

Product/a (ai/a): 0.4 to 0.9 fl oz EC (0.045 to 0.1 oz)

Weeds: Small broadleaf weeds, including pigweed and common lambsquarters.​​​​​​​
When to Apply: POST. Soybean: 1 to 2 trifoliolates. Weeds: Small.
Remarks and Paragraphs: Contact, nonresidual herbicides requiring thorough coverage. Most active in hot and sunny conditions. 
May cause speckling on soybean leaves. Refer to label for crop response, adjuvant type and rate, and tank-mix options.


Cobra
(lactofen)

Product/a (ai/a): 6 to 12.5 fl oz (1.5 to 3.2 oz)

Weeds: Small broadleaf weeds, including pigweed and common lambsquarters.​​​​​​​
When to Apply: POST. Soybean: 1 to 2 trifoliolates. Weeds: Small.
Remarks and Paragraphs: Contact, nonresidual herbicides requiring thorough coverage. Most active in hot and sunny conditions. 
May cause speckling on soybean leaves. Refer to label for crop response, adjuvant type and rate, and tank-mix options.


Resource
(flumiclorac)

Product/a (ai/a): 2 to 3 fl oz EC (0.215 to 0.32 oz)

Weeds: Small broadleaf weeds, including pigweed and common lambsquarters.​​​​​​​
When to Apply: POST. Soybean: 1 to 2 trifoliolates. Weeds: Small.
Remarks and Paragraphs: Contact, nonresidual herbicides requiring thorough coverage. Most active in hot and sunny conditions. 
May cause speckling on soybean leaves. Refer to label for crop response, adjuvant type and rate, and tank-mix options.


Flexstar
(fomesafen + adjuvants)

Product/a (ai/a): 0.75 to 1 pt (0.176 to 0.24 lb)

Weeds: Broadleaf weeds, including pigweed, cocklebur, Venice mallow, mustard, ragweed, kochia, smartweed, EB nightshade.
Poor hairy nightshade control.​​​​​​​
When to Apply: POST. Soybean: Prior to flowering. Weeds: Small.
Remarks and Paragraphs: Contact herbicide requiring thorough coverage. Most active in hot and sunny conditions. Apply at 1 pt/a in  North Dakota east of I-29 and south of I-94 and in Minnesota south of I-94. Use 0.75 pt/a in North Dakota east of Highway 281 and in  Minnesota south of U.S. Highway 2. Areas west of Highway 281 may have a 24(c) to allow for application. Current 24(c) label expires  Dec. 31, 2021. Check CDMS for counties and possible continuation of label. Add MSO at 1% v/v + AMS at 10 lb/100 gal water. Refer to  label for crop rotation restrictions and restrictions for each geographic region. Refer to narrative for improved broadleaf weed control.


FirstRate
(cloransulam)

Product/a (ai/a): 0.3 oz WDG or 10 a/pack (0.25 oz)

Weeds: Venice mallow, cocklebur, horseweed, ragweed, sunflower and wild mustard.​​​​​​​
When to Apply: POST. Soybean: Up to 50% of plants flowering. Weeds: Up to 10 inches tall.
Remarks and Paragraphs: Add NIS at 0.125% v/v or oil adjuvant at 1.25% v/v + 28% UAN at 2.5% v/v. Refer to label for weed size and tank-mix options.


Harmony/generic thifensulfuron

Product/a (ai/a): 0.083 (1/12) oz DF, 0.125 (1/8) oz SG (0.062 oz)

Weeds: Wild mustard, pigweed and lambsquarters. No ALS-resistant weed control.
When to Apply: POST. Soybean: Fully expanded 1st trifoliolate leaf until 60 days PHI.
Remarks and Paragraphs: Add NIS at 0.25% v/v or oil additive at 1 to 2 pt/a+ 28% UAN or AMS. Refer to label for tank-mix options.


Pursuit
(imazethapyr)

Product/a (ai/a): 3 fl oz (0.75 oz ae)

Weeds: Annual broadleaf weeds. Poor common lambsquarters, ragweed, wild buckwheat and biennial wormwood control. No control of  ALS-resistant weeds.
When to Apply: POST. Soybean: Fully expanded first trifoliolate leaf but prior to flowering.
Remarks and Paragraphs: Weeds: Small and actively growing. Add NIS at 0.25% v/v or oil adjuvant at 1 to 2 pt/a + 28% UAN at 2.5%  v/v. MSO adjuvants enhance weed control more than petroleum oil or NIS. Refer to label for weed size and application information. Raptor has less soil residual carryover than Pursuit.


Raptor
(imazamox)

Product/a (ai/a): 4 to 5 fl oz (0.5 to 0.625 oz ae)

Weeds: Annual broadleaf weeds. Poor common lambsquarters, ragweed, wild buckwheat and biennial wormwood control. No control of  ALS-resistant weeds.
When to Apply: POST. Soybean: Fully expanded first trifoliolate leaf but prior to flowering.
Remarks and Paragraphs: Weeds: Small and actively growing. Add NIS at 0.25% v/v or oil adjuvant at 1 to 2 pt/a + 28% UAN at 2.5%  v/v. MSO adjuvants enhance weed control more than petroleum oil or NIS. Refer to label for weed size and application information. Raptor has less soil residual carryover than Pursuit.

NDSU Soybean Micro-rate in Soybean

Rezult B & Rezult G + Raptor + Flexstar + Select/clethodim + MSO adjuvant

Product/a (ai/a): 0.5 to 0.6 pt & 0.5 to 0.6 pt + 1 fl oz + 2 to 4 fl oz + 2 fl oz (optional) + 1.25 pt/a

Weeds: Grass and broadleaf weeds, including kochia, pigweed and nightshade. May not control wild buckwheat.
When to Apply: POST. Weeds: Small. Must be less than 1 to 2 inches tall.
Remarks and Paragraphs: User assumes all risk of inadequate weed control when using this reduced-rate treatment. Must be applied  with MSO or MSO and basic pH blend adjuvants. Select/clethodim can be excluded if grass infestation is low. Refer to narrative and  Rezult section above.


Assure II
Targa

(quizalofop)

Product/a (ai/a): 4 to 10 fl oz (0.44 to 1.1 oz)

Weeds: Annual grasses and quackgrass.​​​​​​​
When to Apply: Soybean: Prior to pod set. Grass weeds: Refer to Grass Control With Post Herbicides in Soybean table.
Remarks and Paragraphs: Add oil adjuvant at 1% v/v but not less than 1.25 pt/a. Oil adjuvant at more than 1 qt/a is not needed. See  Select Max label for detailed adjuvant recommendations. Use highest rate of Assure II for yellow foxtail control. Grass control is reduced  by tank mixtures or close interval application of POST broadleaf control herbicides. Antagonism generally can be avoided by applying a  higher rate of grass herbicide or apply the grass control herbicide 1 or more days before or 7 days after the broadleaf control herbicide. Do not cultivate prior to 5 days before or 7 days after application. Refer to label for tank-mix options.


Fusilade DX
(fluazifop)

Product/a (ai/a): 5 to 12 fl oz (1.25 to 3 oz)

Weeds: Annual grasses and quackgrass.​​​​​​​
When to Apply: Soybean: Prior to pod set. Grass weeds: Refer to Grass Control With Post Herbicides in Soybean table.
Remarks and Paragraphs: Add oil adjuvant at 1% v/v but not less than 1.25 pt/a. Oil adjuvant at more than 1 qt/a is not needed. See  Select Max label for detailed adjuvant recommendations. Use highest rate of Assure II for yellow foxtail control. Grass control is reduced  by tank mixtures or close interval application of POST broadleaf control herbicides. Antagonism generally can be avoided by applying a  higher rate of grass herbicide or apply the grass control herbicide 1 or more days before or 7 days after the broadleaf control herbicide. Do not cultivate prior to 5 days before or 7 days after application. Refer to label for tank-mix options.


Fusion
(fluazifop & fenoxaprop)

Product/a (ai/a): 4 to 12 fl oz (1 to 3 oz & 0.32 to 0.96 oz)

Weeds: Annual grasses and quackgrass.​​​​​​​
When to Apply: Soybean: Prior to pod set. Grass weeds: Refer to Grass Control With Post Herbicides in Soybean table.
Remarks and Paragraphs: Add oil adjuvant at 1% v/v but not less than 1.25 pt/a. Oil adjuvant at more than 1 qt/a is not needed. See  Select Max label for detailed adjuvant recommendations. Use highest rate of Assure II for yellow foxtail control. Grass control is reduced  by tank mixtures or close interval application of POST broadleaf control herbicides. Antagonism generally can be avoided by applying a  higher rate of grass herbicide or apply the grass control herbicide 1 or more days before or 7 days after the broadleaf control herbicide. Do not cultivate prior to 5 days before or 7 days after application. Refer to label for tank-mix options.


Poast
(sethoxydim)

Product/a (ai/a): 0.5 to 1.5 pt (0.1 to 0.3 lb)

Weeds: Annual grasses.​​​​​​​
When to Apply: Soybean: All stages. Grass weeds: Refer to Grass Control With Post Herbicides in Soybean table.
Remarks and Paragraphs: Add oil adjuvant at 1% v/v but not less than 1.25 pt/a. Oil adjuvant at more than 1 qt/a is not needed. See  Select Max label for detailed adjuvant recommendations. Use highest rate of Assure II for yellow foxtail control. Grass control is reduced  by tank mixtures or close interval application of POST broadleaf control herbicides. Antagonism generally can be avoided by applying a  higher rate of grass herbicide or apply the grass control herbicide 1 or more days before or 7 days after the broadleaf control herbicide. Do not cultivate prior to 5 days before or 7 days after application. Refer to label for tank-mix options.


Select/generic clethodim
Select Max
(clethodim)

Product/a (ai/a): 4 to 16 fl oz (1 to 4 oz), 9 to 32 fl oz (1.125 to 4 oz)

Weeds: Annual grasses and quackgrass.
When to Apply: Soybean: All stages. Grass weeds: Refer to Grass Control With Post Herbicides in Soybean table.​​​​​​​
Remarks and Paragraphs: Add oil adjuvant at 1% v/v but not less than 1.25 pt/a. Oil adjuvant at more than 1 qt/a is not needed. See  Select Max label for detailed adjuvant recommendations. Use highest rate of Assure II for yellow foxtail control. Grass control is reduced  by tank mixtures or close interval application of POST broadleaf control herbicides. Antagonism generally can be avoided by applying a  higher rate of grass herbicide or apply the grass control herbicide 1 or more days before or 7 days after the broadleaf control herbicide. Do not cultivate prior to 5 days before or 7 days after application. Refer to label for tank-mix options.

Grass Control With Post Herbicides in Soybean
Herbicide Grass size (inches) Rate (fl oz/a)
Green and yellow foxtail    
   Assure II/Targa 2 to 4 7 to 8
   Fusilade DX 2 to 4 10 to 12
   Fusion 2 to 4 8
   Poast 1 to 8 1 pt
   Select 2 to 8 4 to 6
   Select Max 2 to 6 9
  6 to 8 12
Wild-proso millet    
   Assure II/Targa 2 to 6 5 to 8
   Fusilade DX 4 to 8 6
   Fusion 4 to 8 6
   Poast 4 to 10 0.5 pt
   Select 1 to 10 4 to 6
   Select Max 2 to 6 9
  6 to 8 12
Volunteer corn    
   Assure II/Targa 6 to 30 5 to 8
   Fusilade DX 12 to 24 4 to 8
   Fusion 12 to 24 6
   Poast 1 to 20 1 pt
   Select 4 to 12 4
  12 to 24 6
   Select Max 1 to 12 6
  12 to 24 9
  24 to 36 12
Wild oat, vol. small grains, sandbur    
   Assure II/Targa 2 to 6 7 to 8
   Fusilade DX 2 to 6 8
   Fusion 2 to 6 8
   Poast 1 to 4 1 pt
   Select 2 to 6 6
   Select Max 2 to 6 9
  6 to 8 12
Quackgrass    
   Assure II/Targa 6 to 10 12
   Fusilade DX 6 to 10 12
   Fusion 6 to 10 12
   Poast 6 to 8 2 pt
   Select 4 to 12 8
   Select Max 4 to 12 12

Preharvest Application in Soybean

Roundup/generic glyphosate

Product/a (ai/a): Up to 0.75 lb ae See Remarks.

Weeds: Preharvest weed control.​​​​​​​
When to Apply: Prior to harvest. Apply after pods have set and lost all green. Allow a 7-day PHI.
Remarks and Paragraphs: Add AMS fertilizer at 4 lb/100 gal, or more for hard water. Refer to label for adjuvant use. Do not apply on soybean grown for seed because reduced germination/vigor may occur.


Paraquat
RUP

Product/a (ai/a): 8 to 12 fl oz 2SL, 5.6 to 8.4 fl oz 3SL (0.13 to 0.188 lb)

Weeds: Desiccant.​​​​​​​
When to Apply: Prior to harvest. Paraquat - Allow a 15-day PHI.
Remarks and Paragraphs: Add NIS at 0.125% v/v. Most active in hot and sunny conditions. Apply when at least 65% of seed pods are a mature brown or when seed moisture is 30% or less.


Aim
(carfentrazone)

Product/a (ai/a): 1 to 1.5 oz (0.256 to 0.384)

Weeds: Desiccant.​​​​​​​
When to Apply: Aim - Allow a 3-day PHI.
Remarks and Paragraphs: Add NIS at 0.125% v/v. Most active in hot and sunny conditions. Apply when at least 65% of seed pods are a mature brown or when seed moisture is 30% or less.


Sharpen
(saflufenacil)

Product/a (ai/a): 1 to 2 flo oz

Weeds: Harvest aid/dessicant​​​​​​​
When to Apply: Allow a 3-day PHI.
Remarks and Paragraphs: Add AMS + MSO. Apply when at least 65% of seed pods are a mature brown or when seed moisture is 30%  or less. Do not apply on soybean grown for seed because reduced germination/vigor may occur.

LibertyLink Soybean

 

Liberty 280/generic glufosinate

Product/a (ai/a): 32 fl oz (0.585 lb)

Weeds: Annual grass and broadleaf weeds, including ALS and glyphosate- resistant weeds.​​​​​​​
When to Apply: POST. Soybean: Emergence up to R1 (bloom). Weeds: Up to 3 inches tall.
Remarks and Paragraphs: Apply only to LibertyLink soybean varieties. Nonselective, contact, nonresidual herbicide requiring thorough  coverage. Add AMS at 3 lb/a. Apply with a minimum carrier volume of 15 GPA. Apply with a registered grass herbicide. Refer to label for  tank-mix options and restrictions. Most active in hot and sunny conditions. Controls weeds resistant to other herbicides.

Roundup Ready Soybean

Roundup/generic glyphosate

Product/a (ai/a): Maximum single application = 1.5 lb ae; Maximum in-crop = 2.25 lb ae. See Remarks.

Weeds: Annual and perennial grass and broadleaf weeds.​​​​​​​
When to Apply: POST. Soybean: Emergence through R2 of full flowering. The R2 stage ends when a pod 3/16 inch long at one of the  four uppermost nodes appears on the main stem along with a fully developed leaf (R3 stage). Allow a 14-day PHI.
Remarks and Paragraphs: Apply only to Roundup Ready soybean varieties.

    Maximum - single appl. Maximum - in-crop
lb ae/gal lb ai/gal 1.5 ae 2.25 ae
3 4 = 64 fl oz 96 fl oz
4/4.17 5.4/5.1 = 48 fl oz 72 fl oz
4.5 5.5 = 44 fl oz 66 fl oz
5 6.1 = 40 fl oz 60 fl oz

Add AMS fertilizer at 4 lb/100 gal, or more for hard water. Multiple applications may be necessary for weed flushes. Drift and off-site movement may cause injury or death to other plants and crops. Refer to label for weeds controlled, application information, adjuvant use, tank-mix options with residual herbicides and restrictions. Cannot plant harvested patented soybean seed.

Roundup Ready Xtend (dicamba plus glyphosate-tolerant) Soybean

Engenia, FeXapan, Xtendimax1 RUP
1Only these three products were registered as of March 1 2019. More products may be approved in coming years. Only use products with approved labels for use in Roundup Ready Xtend soybean crops.

Product/a (ai/a): Maximum single application = 1 lb ae, Preemergence, 0.5 lb ae in-crop, Maximum in-crop = 1 lb ae See Remarks.

Weeds: Annual and perennial broadleaf weeds.​​​​​​​
When to Apply: PRE or POST. POST. Soybean: Emergence up to R1, or flowering.
Remarks and Paragraphs: Apply only to Roundup Ready Xtend soybean varieties. Apply up to 1 lb ae pre-emergence in a single application. Apply 0.5 lb ae postemergence, up to two times, for a max of 1 lb ae. Never add AMS fertilizer. See websites of individual products to determine legally allowed tank-mix partners and latest label amendments. The labels for these products are likely to be altered on an annual basis, and yearly training appears to be likely to use these products. Always check with the chemical manufacturer for the latest list of rules.

Enlist (2,4-D plus glyphosate plus glufosinate-tolerant) Soybean

Enlist One
(2,4-D Choline)

Product/a (ai/a): 1.5 to 2 pt/a

Weeds: Annual and perennial grass and broadleaf weeds.​​​​​​​
When to Apply: PRE or POST. POST Enlist One and Enlist Duo: Emergence through R2
Remarks and Paragraphs: Many glyphosate and glufosinate products can be applied to this soybean. Always check labels for legality of application to this soybean. Apply only to Enlist Soybean varieties. Use rate and growth stage comments are valid only for 2019. Always check with manufacturer for latest list of approved nozzles and tank-mixes. These are subject to change on an annual basis. Growth stage of soybean for application also is subject to change in future years.


Enlist Duo
(2,4-D Choline + glyphosate)

Product/a (ai/a): 3.5 to 4.75 pt/a

Weeds: Annual and perennial grass and broadleaf weeds.​​​​​​​
When to Apply: PRE or POST. POST Enlist One and Enlist Duo: Emergence through R2
Remarks and Paragraphs: Many glyphosate and glufosinate products can be applied to this soybean. Always check labels for legality of application to this soybean. Apply only to Enlist Soybean varieties. Use rate and growth stage comments are valid only for 2019. Always check with manufacturer for latest list of approved nozzles and tank-mixes. These are subject to change on an annual basis. Growth stage of soybean for application also is subject to change in future years.


Glufosinate

Product/a (ai/a): 32 fl oz/a See Remarks.

Weeds: Annual and perennial grass and broadleaf weeds.​​​​​​​
When to Apply: Glufosinate: Emergence up to R1
Remarks and Paragraphs: Many glyphosate and glufosinate products can be applied to this soybean. Always check labels for legality of application to this soybean. Apply only to Enlist Soybean varieties. Use rate and growth stage comments are valid only for 2019. Always check with manufacturer for latest list of approved nozzles and tank-mixes. These are subject to change on an annual basis. Growth stage of soybean for application also is subject to change in future years.

LLGT27 (Glufosinate plus glyphosate plus isoxaflutole-tolerant) Soybean

Glyphosate, glufosinate (See Roundup Ready and LibertyLink crop section for comments)

Product/a (ai/a): See Remarks.

Weeds: Annual and perennial grass and broadleaf weeds.​​​​​​​
When to Apply: See Remarks
Remarks and Paragraphs: Many glyphosate and glufosinate products can be applied to this soybean. Always check labels for legality of application to this soybean. As of March 1, 2019, no Group 27 products are labeled for use in this soybean. This is  subject to change as products go through EPA registration. Annual updates will be provided in the “North Dakota Weed Control Guide.” Always check with manufacturers for labeled products and their approved tank-mixes.


ALITE 27
As of this writing, no isoxaflutole product is registered for use in crop.

Product/a (ai/a): See Remarks.

Weeds: Annual and perennial grass and broadleaf weeds.​​​​​​​
When to Apply: See Remarks
Remarks and Paragraphs: Many glyphosate and glufosinate products can be applied to this soybean. Always check labels for legality of application to this soybean. As of March 1, 2019, no Group 27 products are labeled for use in this soybean. This is  subject to change as products go through EPA registration. Annual updates will be provided in the “North Dakota Weed Control Guide.” Always check with manufacturers for labeled products and their approved tank-mixes.

 

Roundup Ready/STS (sulfonylurea-tolerant) Soybean

Refer to Roundup Ready soybean above for use of glyphosate in RR/STS soybean.

Harmony/generic thifensulfuron

Product/a (ai/a): 0.33 oz DF, 0.5 oz SG (0.25 oz).

Weeds: Annual broadleaf weeds, including wild buckwheat, lambsquarters, mustard species and volunteer RR canola.​​​​​​​
When to Apply: POST. RR/STS soybean: 1st fully expanded trifoliolate to 60 days PHI.
Remarks and Paragraphs: Apply only to RUR/STS soybean varieties. Apply with glyphosate at 0.38 to 1.125 lb ae/A. Add NIS at  0.125 to 0.25% v/v to nonloaded glyphosate. Refer to label for adjuvant use. Apply with AMS at 4 lb/100 gal water, or more for hard water. Refer to label for weeds controlled and application information.

Weed Management in Roundup Ready Soybean

NDSU recommends using herbicides with different modes of action and different weed control management practices in Roundup Ready soybean production to delay development of glyphosate-resistant weeds.

COMMANDMENT 1 — Control weeds before 2 to 4 inches tall to avoid yield loss.

Remove weeds early, especially when grass weed populations are high. Some data from the Midwest indicate that soybean yield may not be reduced by delaying Roundup/generic glyphosate application until weeds are up to 6 inches tall. However, data from the northern Plains show that, especially under dry conditions, soybean yield loss will occur if weeds become greater than 4 inches tall prior to Roundup/glyphosate application.

Roundup/glyphosate at 1.5 oz ae/a controls foxtail, 2.25 oz ae/a controls volunteer small grain, and 3 oz ae/A controls wild oat and downy brome. Use higher rates on broadleaf weeds, larger weeds and tolerant weeds, or if weeds are under environmental stress.

Three Systems of Weed Control in RR Soybean

  1. PRE followed by glyphosate POST: All PRE herbicides require rain for activation.
    Tables lists many registered PRE soybean herbicides that can be used in herbicide-resistant soybean. PRE herbicides at 2/3 to the full labeled rate may give 60 to 99 percent control of some grass and broadleaf weeds, will reduce weed infestations emerging with soybean, will allow more flexibility in application of POST herbicides and will help protect yield from early season weed competition.
  2. Roundup/generic glyphosate + POST broadleaf herbicide (different mode of action):
    Several herbicides listed in the following table will improve control of weeds not controlled by Roundup/glyphosate. Roundup/glyphosate has no soil residual and will not control weeds emerging after application. Roundup/glyphosate may not control some weed species or biotypes. Many POST herbicides listed will give residual weed control. Follow label directions for tank-mix and application information.
  3. Roundup/generic glyphosate (EPOST = 2- to 4-inch-tall weeds) followed by Roundup/glyphosate (POST = 14 to 21 days later):
    This program will increase the risk of weed resistance unless other strategies are used in rotational crops.
    The following table shows herbicides to apply in tank-mix or sequentially with Roundup/glyphosate in RR soybean for control of weeds not controlled by Roundup/glyphosate. Weed ratings are control without Roundup/glyphosate. Refer to the label for tank-mix and specific application information. Residual weed control listed in the table refers to control of subsequent flushes of weeds after herbicide application.