Soybeans

Allen County Weed Survey

By Clint Schroeder OSU Extension

Each fall Ohio State University Extension conducts a survey of the different types of weeds present in soybean fields, as well as, the level of infestation. Weed Science State Specialist Dr. Mark Loux leads this study and uses the information gained to help develop future weed management programs. This study is conducted in each county where there is an Ag and Natural Resources Educator. The educator selects a route 80-100 miles long through the county and takes notes on one soybean field in each mile.

Allen County 2019 Weed Survey Results

Continue reading Allen County Weed Survey →

What’s in your Grain Dust?

By Dr. S Dee Jepsen, State Leader of the OSU Extension Agricultural Safety & Health Program

As many farmers know, grain dust contains more than meets the eye. Moreover, the dust you inhale may also contain microbes, insects, and additional plant fodder. All of which are affected by temperature and humidity fluctuations. It is important to better understand what is in your grain dust, since many biological contaminants have been linked to health conditions like asthma and chronic bronchitis. That is why the OSU Extension Agricultural Safety & Health Program wants to sample your grain dust during a loud out period. See below for study details:

  1. We know your schedule is ever-changing, that’s why students will be available both weekdays/nights and weekends for sampling. A half day notice will suffice to allow for travel time
  2. Samples may be taken of multiple bins, storing different grains
  3. No preparation is needed for sampling!
  4. Sampling will not interfere with the load-out process.
  5. Measurements will only be taken during the unloading process.
  6. You will receive a dust analysis report ~1 week later showing the amount of Total Dust and Respirable Dust. Results are anonymous, and will not be shared with any other agencies.
  7. There is no fee for this service, and no incentives to participate, besides contributing to our understanding of dust level exposure. N-95 respirators are available upon request.

If you are interested in participating, please contact Dee Jepsen by phone at 614-292-6008 or by e-mail at jepsen.4@osu.edu.

Frogeye Leaf Spot – Is It Worth Spraying in 2019?

By:  Anne Dorrance, Ohio State University

Frogeye leaf spot

Several reports over the last two weeks of heavy frogeye leaf spot pressure in some fields as well as low to moderate pressure in others.  This disease will continue to increase and infect new foliage as it develops on these late planted soybeans. Based on our previous research, only once (2018) in 14 years of studies did applications at the soybean growth stage R5 contribute to preserved yield.  At the R5, the leaf at the terminal is fully developed and the pods at any one of the top four nodes is fully expanded, but the seeds are just beginning to expand.

Soybeans that have frogeye and have just begun to flower, are at full flower, or have just reached the R3 growth stage, these decisions are going to be challenging.  In full disclosure, we don’t have data or examples to rely on here.  This late planting and late development is all new territory for all of us.  But there are some sound principles to rely on.

For soybeans that are in the R3 growth stage, pods are tiny, 3/16 of an inch at one of the four uppermost nodes of the plant. This is the time if frogeye leaf spot can easily be found in the canopy, a lesion on one plant every 40’ has in our studies, preserved yield in a normal growing season.  This growth stage in Ohio typically occurs in mid to late July on May planted soybeans.

So here are the questions to address for 2019 and in the order of importance.

  1. The value of the crop – are these soybeans grown for seed, then yes error on the side of caution and apply the fungicide and make a second application 14 days later.
  2. Are these soybeans under contract, and will you actually be able to sell them? If the answer is no, then adding more inputs into the crop may not be a sound investment.
  3. Will the soybean finish making grain before harvest? This question will most likely affect soybeans that are just now in full flower, we are hoping for a very long fall, but this will impact the return on applying the fungicide.
  4. How susceptible is the variety? For some resistant varieties, the frogeye leaf spots are small and only a few will form on each leaf.  So double check with your seed supplier to look at the ratings. In any event your seed dealer will want to watch this variety and work with their breeders.

If you do decide to spray, please leave unsprayed check strips – at least 3 separate locations in the field and collect the yield off each of these separately, the same is true for the fungicides sprayed strips, collect the data from these as well.  The yield maps will be especially important this year.  Secondly, choose the cheapest triazole fungicide that you can find.  This is going to be very important for the economic viability of this year’s crop. Also remember, we have detected QoI resistance in Ohio, and it is not advisable to spray these types of fungicides at these late dates on crops that are further behind in development.

If you don’t spray, and it is a highly susceptible variety, the disease will continue to increase on the plants, but only if periodic rains and heavy dews or fogs continue through the remainder of this crazy field season. Mark this field and this variety. These are important considerations for 2020 field season as this disease does now overwinter in Ohio. Replanting in the same field with the same variety or one that is susceptible to this disease is a recipe for further yield loss in the future.

Frogeye leaf spot

No pigweed left behind – late-season scouting for Palmer amaranth and waterhemp

By:  Mark Loux, Ohio State University

If you don’t already have to deal with waterhemp or Palmer amaranth, you don’t want it.  Ask anyone who does.  Neither one of these weeds is easy to manage, and both can cause substantial increases in the cost of herbicide programs, which have to be constantly changed to account for the multiple resistance that will develop over time (not “can”, “will”).

Palmer amaranth in a Tennessee field. Source: Lisa Behnken

Palmer amaranth in a Tennessee field. Source: Lisa Behnken

The trend across the country is for Palmer and waterhemp to develop resistance to any new herbicide sites of action that are used in POST treatments within about three cycles of use.  Preventing new infestations of these weeds should be of high priority for Ohio growers.  When not adequately controlled, Palmer amaranth can take over a field faster than any other annual weed we deal with, and waterhemp is a close second.  Taking the time to find and remove any Palmer and waterhemp plants from fields in late-season before they produce seed will go a long way toward maintaining the profitability of Ohio farm operations.  There is information on Palmer amaranth and waterhemp identification on most university websites, including ours –  u.osu.edu/osuweeds/ (go to “weeds” and then “Palmer amaranth”).  An excellent brief video on identification can be found there, along with an ID fact sheet.  The dead giveaway for Palmer amaranth as we move into late summer is the long seedhead, and those on female seed-bearing plants are extremely rough to the touch.  We recommend the following as we progress from now through crop harvest:

– Take some time now into late summer to scout fields, even if it’s from the road or field edge with a pair of binoculars.  This would be a good time to have a friend with a drone that provides real-time video, or your own personal satellite.  Scouting from the road is applicable mostly to soybean fields, since corn will often hide weed infestations.  Scout field borders and adjacent roadsides, areas that flood or receive manure application, and also CREP/wildlife area seedings.  The latter can become infested due to contaminated seed produced in states where Palmer amaranth and waterhemp are endemic and not considered noxious.  Reminder – ODA will test any seed used for these purposes for the presence of Palmer amaranth.

– Walk into the field to check out any weeds that could be Palmer amaranth, waterhemp, or are otherwise mysterious.  If you need help with identification, send photos to us or pull plants and take them to someone who can identify them.  Palmer and waterhemp are considerably different in appearance than giant ragweed and marestail, the other two most common late-season offenders.

– Where the presence of Palmer amaranth or waterhemp is confirmed, check to see whether plants have mature seed (in Palmer infestations these are the rough female seedheads), by shaking/crushing parts of the seedhead into your hand or other surface that will provide contrast.  Mature seed will be small and very dark.  Plants without mature seed should be cut off just below the soil surface, and ideally removed from the field and burned or composted.  Plants with mature seed should be cut off and bagged (at least the seedheads) and removed from the field, or removed via any other method that prevents seed dispersal through the field.

– If the Palmer amaranth or waterhemp population is too dense to remove from the field, some decisions need to be made about whether or how to mow or harvest.  Harvesting through patches or infested fields will result in further spread throughout the field and also contamination of the combine with weed seed that can then be dispersed in other fields.  So consider: 1) not harvesting areas of the field infested with Palmer amaranth or waterhemp, and instead mowing several times to prevent seed production, and 2) harvesting the infested field(s) after all other fields have been harvested, and cleaning the combine thoroughly before further use.  This also applies to any infestations that are discovered while harvesting.  At least one equipment manufacturer has a good video about how to most thoroughly clean a combine.

– Feel free to contact OSU weed science for help with identification or management of Palmer amaranth and waterhemp.  Mark Loux – loux.1@osu.edu, Bruce Ackley – Ackley.19@osu.edu.

Prospects for Soybean Demand

By Todd Hubbs, Department of Agricultural and Consumer Economics, University of Illinois “Prospects for Soybean Demand.” farmdoc daily (9):138

Uncertainty regarding soybean acreage and yield potential will continue to be significant factors in soybean price movements through harvest.  Without a severe crop shortfall, higher soybean prices rely on demand prospects over the next year.

Soybean crush slowed in the final quarter of the current marketing year.  The USDA lowered 2018-19 marketing year crush by 15 million bushels to 2.085 billion bushels in July.  Estimates of monthly soybean crush from the USDA through May totaled 1.58 billion bushels.  The NOPA crush report indicated a June crush of 148.8 million bushels.  For this marketing year, USDA monthly crush numbers have run approximately 6 percent above NOPA crush report estimates.  At this rate, June crush equaled 158 million bushels and brought the total crush for the first ten months of the marketing year to 1.734 billion bushels.  Crush during the last two months of the marketing year needs to total 350 million bushels to reach the USDA projection, on par with totals crushed in the previous year over the same period.

The USDA estimates soybean exports this marketing year at 1.7 billion bushels, down 434 million bushels from the 2017-18 marketing year.  As of July 25, exports totaled approximately 1.54 billion bushels.  Outstanding sales sit at 315 million bushels with 173 million bushels slated for China.  Export inspections need to average 30.2 million bushels per week over the remainder of the marketing year to hit the USDA estimate.  Inspections averaged 29.5 million bushels over the last four weeks.  The current pace of exports appears to be slightly below the pace to meet the USDA estimate.  Based on the latest consumption levels, ending stocks look certain to exceed one billion bushels at the end of August.

Soybean demand over the next year depends on China.  The current state of Chinese tariffs on U.S. soybeans and the continuing spread of African Swine Fever does not bode well for U.S. soybean exports.  Resumption of negotiations with China this week provides some hope for a resolution to the trade impasse.  China’s approval of goodwill purchases totaling approximately 110 million bushels offers some support for exports.  Chinese soybean purchases remain contingent on progress in negotiations.  Based on previous negotiation outcomes, a decent probability exists that tariffs stay in place through the next marketing year.

The outbreak of African Swine Fever in China last year led to the Chinese hog herd dropping nearly 20 percent in 2019.  Prospects of an additional 10 percent reduction in 2020 and a 30 percent drop in the sow herd indicate the current outbreak may take many years to resolve.  Reports from the World Organization of Animal Health (OIE) indicate the disease continues to spread in Asia and parts of Europe.  In Asia, reports of ongoing outbreaks of the disease in Vietnam, Mongolia, Laos, Cambodia and North Korea point toward a long-run continuation of the disease in the region.  Lower pork consumption, substitution from other protein sources, and pork imports look to take up the slack in Chinese pork production.  A rapid escalation of U.S. pork imports to China expected at the start of the year failed to materialize, but expectations of increased pork exports in the latter half of 2019 remain in place.  A larger herd in the U.S. supplying Chinese protein needs supports soybean crush.  However, reduced soybean exports to China due to lower feed demand and tariffs point toward another marketing year of weak exports.  The forecast for Chinese soybean imports during the 2019-20 marketing year come in near 3.2 billion bushels, up slightly from last year and around 260 million bushels less than seen before the disease outbreak.

In conjunction with the prospects of weak demand from the world’s largest soybean importer, soybean production in South America is forecast up 2.3 percent in 2020 at 6.8 billion bushels.  Brazil’s production forecast sits at 4.5 billion bushels, up 220 million bushels over the estimate for the 2018-19 crop.  Another good crop year in South America creates a highly competitive export environment in 2020.

The USDA projects the 2019-20 marketing year consumption levels for crush and exports at 2.115 and 1.875 billion bushels, respectively.  Large livestock herds look to support domestic soybean meal use despite the potential for lower soybean meal exports.  Expansion in biodiesel production supports soybean oil use from crush as well.  Reduced Chinese demand combined with larger South American soybean crops places the current export forecast in question.  Outstanding sales for the 2019-20 marketing year came in at 111 million bushels through July 18 and lagged last year’s total by approximately 250 million bushels.

The potential for a sharply lower soybean crop in 2019 remains a possibility.  Reduced yield potential due to late-planting and lower acreage point to a smaller crop.  A national average yield near 44.7 bushels per acre is necessary to reduce ending stocks to 500 million bushels under current acreage and consumption scenarios put forth by the USDA.  Under a lower demand scenario, the yield must fall further.  Pricing some new crop soybeans on rallies this summer may be prudent.

YouTube Video

Discussion and graphs associated with this article available here: https://youtu.be/meqzOF_OiJQ

Crop Scouting a Delayed Crop

By: Clint Schroeder

The 2019 growing season continues to present new challenges for Ohio farmers. The late planting coupled with localized extreme weather events has changed the way we need to think about scouting for disease and pest issues in our crops.  The good news is that the late planting will delay the corn crop enough that we should not have to worry about Japanese Beetles feeding on corn silks at pollination time. The bad news is that we have had more time for spore counts to build up for foliar diseases like gray leaf spot, northern corn leaf blight, and common southern rust.  In a normal year we would look for disease pressure around tasseling, but this year we could start to see infection at the V8-V12 growth stages. If the hybrid is susceptible and conditions become favorable, high levels of infection at V8-V12 will result in greater and more rapid diseases development, and consequently, greater damage to the upper leaves before grain-fill is complete.  Research by OSU Extension since 2010 has shown that the ideal time to treat with a fungicide is at the VT/R1 even if there is presence of disease prior to that stage. Growers also need to be aware that there is a new foliar disease that showed up in Northwest Ohio in 2018. Tar spot is more likely to show up in no-till fields and can be identified by the raised circular black lesions.

It’s also time to scout for western bean cutworm (WBC) egg masses. I am currently monitoring two traps in Allen County and reporting those numbers to our state office.  Last week there was an average of 7 moths in the traps locally, but the state average was 25.3 moths per trap.  It will be interesting to see if the numbers continue to rise or if we taper off similar to 2018. WBC egg groups are often found on the upper leaf surfaces in clusters. The eggs are round and first appear white, then gradually turn a dark purple. Once eggs turn purple, they will hatch within 24 to 48 hours. If infestations exceed the threshold level, over 8% of plants having eggs or larvae, many insecticides are available to treat with. However, as with any ear-burrowing caterpillar pest, timing is critical. Insecticide applications must occur after egg hatch, or after tassel emergence, but before caterpillars enter the ear. If eggs have hatched, applications should be made after 95% of the field has tassel. If eggs have not hatched, monitor for the color change. To search for larval injury after it has occurred, search the corn for ears having feeding holes on the outside of the husks.

Figure 2. Average western bean cutworm (WBC) per trap in monitoring counties in Ohio for 2016 (blue), 2017 (red), 2018 (green) and 2019 (purple).

Average western bean cutworm (WBC) per trap in monitoring counties in Ohio for 2016 (blue), 2017 (red), 2018 (green) and 2019 (purple).

In soybeans we need to be scouting for insect pressure.  We’ve had a lot of Japanese Beetles present this year and they will do damage by eating the foliage of bean plants.  As a general rule of thumb treatments are warranted when defoliation exceeds: 40% prior to bloom, 15% from bloom to pod-fill, and 25% after pod-fill to plant yellowing. Another pest that we need to be looking for is the brown marmorated stink bug. Adults are speckled brown-gray with a white band on its antennae. There are dark and white bands around the edges of the abdomen, with the whitish markings appearing as triangles. Early nymphs have a dark head with an abdomen that is orange and red with black stripes down the middle. Later nymphs are brown with a white band on its antennae and strong white bands on its legs. The underside of the nymphs is characteristically white.

Adult brown marmorated stink bug. Brown marmorated stink bug nymph.

These bugs will damage soybeans by puncturing tissues with their piercing and sucking mouthparts, and then extracting plant fluids. They prefer to feed on the young pods and developing seed within.  This can cause significant yield loss as the seed will become shriveled and deformed. Scouting for this pest should ramp up as soybeans begin to flower.  Given the late planting we have experienced it might be possible that the insect pressure will require multiple insecticide treatments to protect yield potential.

For more information on these pests or any other things you might be seeing this year please contact us at 419-879-9108. I know in these conditions it is often times frustrating trying to decide on treatments for a crop that doesn’t have great yield potential.  I’d be more than happy to come out and talk about the threshold levels OSU Extension has set for treatments and the economics behind that. It is also important to remember that we need to be using our insecticides and fungicides responsibly to prevent not only resistance, but also negative public sentiment.

 

Japanese Beetle Treatment Guidelines

BY: John Obermeyer, Purdue Extension

News flash … Japanese beetle have been emerging and can be seen throughout the state on corn and soybean plants. OK, not that news worthy. How about … some areas of state are seeing tremendous numbers of beetles while some areas aren’t that excited. Again, old news, as this happens every year. Here is a headline sure to grab attention … Japanese beetle – their presence and damage is usually perceived worse than it is. Please refer to the following treatment thresholds.

Field Corn: Japanese beetle feed on corn leaves, tassels, and silks. Generally, leaf and tassel feeding can be ignored. If beetles are present and feeding on corn silks, an insecticide should be applied only if on average the silks are being cut off to less than 1/2 inch before 50% pollination has taken place. This rarely happens on a field-wide basis. Don’t be overly excited by this pest’s tendency to clump on a few ears within an area and eat the silks down to the husks. With sufficient soil moisture, silks will grow from 1/2 to 1 inch per day during the one to two weeks of pollen shed. Silks only need to be peeking out of the husk to receive pollen. Besides, beetles are often attracted to silks that have already completed the fertilization process even though they are still somewhat yellow. Check for pollen shed and silk feeding in several areas of the field, Japanese beetles tend to be present only in the outer rows of the field. Don’t be influenced by what you think you may see from windshield surveys! Get out into fields to determine beetle activity. Be sure to walk in beyond the border rows before drawing any conclusions.

 

Japanese beetle “parties” on selected ears may give false impressions of pollination problems for the whole field

Japanese beetle “parties” on selected ears may give false impressions of pollination problems for the whole field.

 

Soybean: Soybean plants have the amazing ability to withstand considerable leaf removal (defoliation) before yield is impacted. The impact of defoliation is greatest during pod fill because of the importance of leaf area to photosynthesis, and ultimately to yield. Therefore, approximately 15-25% defoliation from bloom to pod fill can be tolerated before yields are economically affected This defoliation must occur for the whole plant, not just the upper canopy. The beetles often congregate in areas of a field where they are first attracted to weeds such as smartweed. Typically, if economic damage occurs, it is only in these areas. Therefore, spot treatments should be considered. Don’t be overly alarmed by these bright, iridescent beetles that feed on the top canopy of the soybean plants. Consider that as they feed their defoliation allows for better sunlight penetration into the lower plant canopy!

 

Japanese beetle will move to new feeding locations, notice how the new growth of these plants have very little damage

Japanese beetle will move to new feeding locations, notice how the new growth of these plants have very little damage.

 

Kill the beetles to prevent grubs?: Japanese beetle develop from grubs that fed on organic matter and/or the roots of plants last fall and this spring. Therefore, it seems logical that killing adult beetles one year should prevent grub damage the next. At least some farmers have explained this to me to justify sub-economic damage in a field. However, it simply doesn’t work that way. Entomologists for decades have been trying to understand this fickle creature. Basically, the adults feed, mate, and lay eggs when and where they want to. The grubs are just as unpredictable. Research attempts to correlate grub presence to crop damage have been inconclusive. Damage does occur, but we are just not usually able to predict when or assess how much. Consider that each beetle mates and lays eggs several times during its oviposition period. To prevent egg laying in a field, one would need to treat multiple times during July and August, which is not economic or practical. If you are wondering, seed-applied insecticides, i.e., Poncho and Cruiser, provide some suppression of white grubs

Prevent Plant, Cover Crops, and More

Last night I was in attendance as a panel of experts talked us through a lot of the issues we are facing in agriculture this spring/summer.  The event was put on by OSU Extension and Ohio No-Till Council and held at the McIntosh Center on the campus of Ohio Northern University.  We’re also thankful that the Ohio Country Journal was on hand to record the panel and you can watch the video at their website, ocj.com. I’m going to try and summarize some of the issues, but if you have specific questions please get in contact with the extension office by calling 419-879-9108.

  1. If you have livestock and are running low on forages now, or anticipate a need before this winter what are your options? You can plant a forage crop on prevented plant acres and harvest it after September 1st under the new RMA/crop insurance guidelines. In this scenario corn is eligible to planted and chopped for silage.  However, you need to check with your crop insurance adjuster on what exactly is allowable so that you do not jeopardize your prevent plant payment. A common recommendation seems to be to plant the corn in 20″ rows or narrower and increase planted populations to 40,000 seeds per acre or higher.  Again, check with your agent/adjuster to make sure you are in compliance.  Other popular forage options are sorghum/sudan grass and oats.  If you are interested in either of these crops please try to get your seed ordered as soon as possible as supply will get tight.
  2. What can I do with treated soybean seed that is not returnable to the dealer? By far, the best option is to plant them, even as just a cover crop.  There are concerns about the insecticide used and what is the maximum rate that they can be planted at.  We would prefer rates of no more than 300,000 seeds per acre. This seed also needs to be covered so that it isn’t creating a harmful impact to wildlife or pollinators.  If you plan on broadcasting the treated seed you will need to incorporate it with either a disk or vertical tillage tool.  We do not recommend trying to carry seed over for planting in 2020.  The 2018 crop had some issues with poor germination scores already and those scores will only get worse even if the seed is stored under ideal conditions (less than 50 degrees and 50% humidity).
  3. What are my options on trying to kill some of these larger weeds that have grown up in preventive plant fields? Mowing them down would be the cheapest option, but most time consuming.  It will also scatter the weed seed and prolong your problem.  Tillage is an option, but it will probably take several passes to get everything killed.  There are lots of herbicide options available, but we need to be cautious on what the plant back intervals are for each herbicide used.  Most of the fields will have at least one species of weeds that is resistant to glyphosate so we need to be using higher rates and tank mix partners.  We also need to be aware of sensitive crops or gardens that might be impacted by drifts or temperature inversions if we are using Dicamba or 2,4-D products.  Mowing first will not make the weeds easier to kill with a herbicide later.
  4.  Are there any cost sharing opportunities for planting cover crops from soil and water districts or USDA – NRCS? The NRCS today has announced that they have $4 million available to producers that plant a cover crop.  Details are still coming out as far as payment amounts and eligibility requirements.  As more information becomes available it will be shared with producers.
  5. How has the excessive rain impacted my soil health? The rains have diminished our soil structure no matter what management practices are in place on your farm.  No air has been incorporated into the soil and this is greatly impacting the natural soil biology. We need to start the recovery process this summer on those acres.  Do not let them sit fallow until next spring.  Get your soils tested and then use this opportunity to apply lime and gypsum if needed.  This might also be an opportunity to apply manure on fields with low phosphorous levels.

I also want to take this opportunity to thank the Lima and Allen County community for the warm welcome I’ve received over the last couple of weeks.  I’m really excited to meet more of you in the ag community here.  I’m currently looking for some volunteers that would let me come out to their farm and pull samples for some research OSU is doing on soybean cyst nematodes. We need to stay ahead of this pathogen so we can continue to develop resistant varieties.  If you are interested please contact me via email at schroeder.307@osu.edu or by calling the extension office at 419-879-9108.

Wet Weather and Soybean Stands

By:  Laura Lindsey and Alexander Lindsey, Ohio State University

Saturated soils after soybean planting can cause uneven emergence and stand reductions of varying extent depending on the stage of the soybean plant and other environmental factors including temperature and duration of saturated conditions. Additionally, increased disease incidence may further reduce plant stand.Flooded soybean field

Saturated Soil Prior to Germination: While soil moisture is necessary for germination, soybean seeds will not germinate when soils are saturated because oxygen is limiting.

Saturated Soil during Germination: Saturated soils during soybean germination may cause uneven emergence. In a laboratory study, soybean germination was reduced by ~15% after only one hour of flood conditions (Wuebker et al., 2001). After 48 hours of flood conditions, soybean germination was reduced 33-70% depending on when imbibition (seed taking up water) began relative to the flooding conditions. Practically, for Ohio, this means if soybean seeds were further along in the germination process when flooding occurred, the seeds will be more susceptible to flooding stress.

Saturated Soil during Vegetative Stage: Warmer temperatures will cause soybean plants to die faster. At temperatures, 80 degrees and greater, submerged soybean plants will likely due in 24 to 48 hours. However, cool, cloudy days (…and we’ve had plenty this year) and clear nights increase the survival potential of a flooded soybean crop. Flooded plants may also exhibit poor nodulation, resulting in yellow, stunted plants.

Evaluate Stand: To quickly estimate stand, count the number of plants in 69’8” of the row for 7.5-inch row spacing, 34’10” for 15-inch row spacing, or 17’5” of the row for 30-inch row spacing. These counts represent 1/1000th of an acre (i.e., 120 plants in 7.5-inch row spacing = 120,000 plants/acre).

Keep in mind, the effect of plant population on yield is very small over the normal range of seeding rates. For soybeans planted in May, final populations of 100,000 to 120,000 plants/acre are generally adequate for maximum economic return. For example, in our seeding rate trials in Clark County, 100% yield (77 bu./acre) was achieved with a final plant stand of 125,000 plants/acre. However, a 95% yield (73 bu./acre) was achieved with only 77,000 plants/acre. (This trial was planted the second half of May in 15-inch row width.)

Source:

Wuebker, E.F., R.E. Mullen, and K. Koehler. 2001. Flooding and temperature effects on soybean germination. Crop Sci. 41:1857-1861.