Late season, The Bean Report

The Bean Report – August 16, 2023

AUGUST 16, 2023

Crop Update

  • Soybeans range from R5.5 to R6 (full seed) with lower leaves dropping.
    • Rainfall last week was very welcome for soybeans as they were filling seeds. Moisture for pod filling stages (R5-6) is critical to soybean yield. Plants experiencing moisture stress will mature earlier, reducing seed weight and the number of seeds per pod.
    • Spider mites have been noted in greater numbers in some fields. The threshold for control is more than 20% of leaves affected. Since they are often congregated to field edges or patches, spot spraying is often effective. The insecticide option for control is dimethoate (Cygon, Lagon), which has a 30-day pre-harvest interval.
    • Once soybeans have reached R6 (full seed), they are considered safe from soybeans aphids.
    • Disease pressure has been low across the province. Phytophthora root rot and northern stem canker are showing up more often in fields with tighter soybean rotations or in areas of poor drainage. If large amounts of Phytophthora symptoms are noted in a field, consider sending soil for pathotype testing. This soil test will tell you the best major gene resistance to use in that field in future years to aid in variety selection. Scouting and Management of Phytophthora Root Rot →
    • Patches of potassium (K) deficiency are visible in soybeans growing on sandier soils during pod filling stages. Symptoms are chlorosis of the leaf margins are soybeans are moving K from the leaves to the seeds. In previous research in Manitoba, soybean yields have not responded to K fertilizer treatments at low-K sites. Soybeans remove large amounts of K in the seed (1.1 – 1.4 lbs K2O/bu) so it is important to balance K fertility throughout the rotation to support yields of other crops.
  • Field peas range from R6.5 to R7 (full maturity). Pea harvest is on-going.
    • Peas are ready for harvest when overall seed moisture is 18 to 20%. The maximum safe storage moisture for peas is 16%. Aeration in the bin is typically used to reach this safe storage moisture. Pea Desiccation and Harvest Guide →
    • Peas usually sweat after going in the bin, so monitor for moisture build-up or spoilage post-harvest.
  • Dry beans range from R7 (full seed) to R9 (full maturity).
    • Desiccation may be necessary for dry beans depending on the evenness of maturity across the field and if late-season weed control is needed due to the risk of seed staining. If desiccating, target the R9 (full maturity) stage when 80% of leaves have dropped and 80% of pods had changed to their mature colour in the greenest areas of the field. Seeds in the youngest pods will have lost their green colour when split in half. Dry Bean Desiccation and Harvest Guide →
  • Faba beans range from R6 (beginning maturity) to R7.5 (mid to late maturity).
    • Lygus bugs cause perforation damage in faba beans, reducing seed quality. Faba beans are susceptible to lygus damage until seeds and pods are firm enough that lygus cannot penetrate them any longer.

Desiccation Decisions

Crop desiccation has become an increasingly hot topic. In part due to consumer demand for pesticide-free products, variable maximum residue limits (MRLs) across export markets and the negative spotlight on glyphosate. It doesn’t mean desiccation is off-limits. But we need to understand the limitations of late-season herbicide. Especially when it comes to crops destined for human consumption, including field peas and dry edible beans.

Some questions to ask before applying that late-season herbicide:

  • Is it a stagey crop with areas maturing at different rates?
  • How far away from harvest is the majority of the crop?
  • Are there weeds that need to be controlled?
  • What are the weather conditions like during maturity?
  • What grade are you targeting?
  • What crop are you planning to grow after?

For more discussion on these questions and more, check out Successful Desiccation Decisions in Peas and Beans →

Desiccation Timing for Dry Beans

Dry beans are ready for desiccation once they’ve reached R9 (full maturity). At this stage, plants will have:

  • 80% pod colour change,
  • 80-90% leaf drop, and
  • <30% seed moisture in the least mature parts of the field.
    • What does that mean? At <30% seed moisture, seeds will rattle within the lowest pods, upper pods will be yellow and the seeds within the upper pods will have lost their green colour when split.

Download the Dry Bean Desiccation and Harvest Guide →

Consult with you buyer about the best product option and potential product limitations. Many bean dealers are no longer accepting pre-harvest glyphosate on dry beans.


Maintaining Pea Seed Quality

Cracked seed coats.

Your harvest operations and weather during harvest can affect seed quality which is important for marketing peas. A few grading factors to keep in mind this harvest are:

  • Crack seed coats and splits: These occur when seed is too dry and/or cylinder or rotor speeds are too high. Harvesting at 18-20% seed moisture and slowing cylinder speed with drier grain can reduce seed damage. Run combine and grain cart augers at low speeds and at full capacity.
  • Shrivelled seed: Seed appears dimpled and shrunken, due to plant senescence while seed was immature. Carefully timed swathing or desiccation will avoid this issue.
  • Bleaching: A grading factor only in green peas, bleaching is caused by excessive moisture (rainfall or humidity) at crop maturity, causing a yellow colour on the cotyledons. Desiccation and prompt harvest can reduce the risk of bleaching.
  • Earth tag: A greater issue in peas than in other crops due to the nature of harvest and the texture of the seed coat (which retains dirt).  If you are finding earth tag on the seed, check for soil sticking to the flighting on your combine augers.  Reduce earth tag by minimizing green or dewy plant material passing through the combine and if necessary, lift the cutting bar.
  • Pink peas: Hail can damage pods and allow the bacteria Erwinia Rhapontici to enter and stain peas pink.
  • Soybean contamination: Some pea buyers have strict restrictions on soybean contamination in their pea contracts due to the challenge of cleaning soybeans out of peas and since soybeans are an allergen and GMO crop. Combine Clean-Out: How to Reduce the Risk of Soybeans in Your Peas →
  • Spoilage: As the peas enter the bin, measure the grain temperature and moisture.  If the initial temperature and moisture are within the “no spoilage” zone of Figure 3, grain can be safely stored for up to five months.  A general recommendation is to use aeration fans to condition, cool and dry the crop to at least 16% moisture and 15°C.

Estimating Soybean and Dry Bean Yields

Number of pods on one soybean plant.

Once beans reach or surpass the full seed stage (R6 for soybeans, R7 for dry beans), yields may be estimated. The MPSG Bean App has a yield estimator tool that will do the calculations for you. Download this app (search MPSG Bean App) from the app store or google play.

  1. Estimate the average plant population in the field by taking plant counts.
  2. In a few areas, count and average the number of pods per plant.
  3. Within pods, count and average the number of seeds per pod.
  4. Estimate seed size – typically, use your variety’s seed size and adjust for environmental conditions (dry conditions means smaller seed size, so more seeds per lb)

Yield (lbs/ac) = plants/acre * pods/plant * seeds/pod ÷ seed size (seeds/lb)
(for soybeans divide yield by 60 for bu/ac)

Yield estimates are only as good as the number of counts taken. Yields are highly variable within fields, so increasing the number of counts and taking counts from different areas can improve the accuracy of estimates.

On-Farm Network: In-Season Results

At this point in the growing season, pea harvests of on-farm fungicide, seeding rate and seed treatment trials are underway. The only remaining data to collect this season are late-season plant counts in soybean seeding rate and row spacing trials and lowest pod heights in the dry bean nitrogen trial. What did we see this year in terms on in-season data collected at our 56 trials?

  • Soybean seeding rate trials: There are 13 seeding rate trials comparing low, medium and high seeding rates on-farm. Germination tests at seeding ranged from 87 to 98%, while early-season establishment from the seeding rate ranged from 68 to 147%.
    • Low plant populations established ranged from 86,000 to 147,000 plants/ac.
    • Medium plant populations established ranged from 106,000 to 156,000 plants/ac.
    • High plant populations established ranged from 122,000 to 181,000 plants/ac.
  • Soybean row spacing trials: One trial is comparing 15 vs 30″ rows while a second is comparing 7.5 vs 15″ rows. Plant populations averaged 145,000 and 136,000 plants/ac, respectively. Canopy closure and weed suppression measurements are currently being analyzed.
  • Soybean inoculant trials: Among seven double (granular in-furrow + liquid on-seed) vs. single (liquid on-seed alone) inoculant trials, there were no significant differences in nodulation ratings. In four single (liquid on-seed) vs. none (bare seed) inoculant trials, there were also no differences in nodulation ratings. With the exception of one trial, all nodulation ratings were above 3.2 (on a scale of 0-4, with 4 being excellent).
  • Dry bean inoculant and nitrogen trials: There were no significant differences among nitrogen rates or inoculant treatments this year. At one trial, dry beans averaged 27 nodules per plant, while at the other trials it was an average of less than 3 nodules per plant. A maximum amount of over 100 nodules on a single dry bean plant was noted while rating for nodulation.
  • Pea seed treatment trials: Compared to untreated peas, Rancona Trio reduced the percent of pea plants infected with a root rot at V6 by 10 – 15% at the two trials in the ground in 2023. The severity of root rot was also less, however root rot severity was quite low (<1 on a 0-9 scale) overall. One trial also evaluated the effect of including an imidacloprid insecticide in the seed treatment to combat pea leaf weevils. There were no significant differences in the number of leaf notches per plant at V6 nor the number of healthy nodules at R3, however in both cases the insecticide treatment did have on average less notches and more nodules, just not a significant improvement over the untreated.
  • Pea seeding rate trials: One trial is comparing established plant stands of 4.2, 4.9 and 5.1 plants/sqft in Chrome peas and a second is comparing 5.4, 6.1 and 7.1 plants/sqft in Lewochko peas.
  • Pea fungicide trials: At seven trials comparing a single application vs. none in peas, the percent of plants with stems infected by Mycosphaerella blight was reduced with a fungicide application by 5 to 40% (11% on average). Severity of both foliar and stem infections were also reduced. Despite being a drier year, there appears to be the potential for yield differences in these trials.
  • Soybean fungicide trials: Two trials comparing soybeans treated with a single application of Veltyma vs none. Disease pressure has been quite low at these trials, with no diseases expected to be yield limiting. At one trial where northern stem canker occurred, treated soybeans had 5% fewer plants infected (8% vs. 13%).
  • Dry bean fungicide trials: The only disease noted in these trials was bacterial blight, which is not expected to be controlled by a fungicide application.
  • Soybean biological trials: There are seven trials in soybeans testing out different biological products to explore if they will have an effect on yield. Stay tuned in the fall for results!

Please note that these data are preliminary and will be finalized later this fall once the single-site reports are made available in the On-Farm Network Results Database →

Canadian Grain Commissions’ Harvest Sample Program

You can sign up to receive a harvest sample kit to submit your crop to the CGC for an assessment of your grain’s quality at no cost. Results can be used when marketing and delivering your grain. Mail your samples following harvest. CGC accepts samples until November 30 and results are available within 20 days.

Quality results include:

  • Unofficial grade
  • Protein content on barley, beans, chickpeas, lentils, oats, peas and wheat
  • Oil and protein for mustard seed and soybeans
  • Dockage assessment on canola
  • Oil, protein and chlorophyll content for canola
  • Oil and protein content and iodine value for flaxseed
  • Falling number for wheat and rye
  • Vomitoxin (deoxynivalenol or DON) levels for wheat, corn and barley