Early September Frost – What is Going to Happen to My Soybeans?

September 5, 2017  – Pinawa, Winnipeg, Whiteshell and Steinbach overnight forecasts, Environment Canada is stating there is a risk of frost. 

Whether or not there is yield loss in soybeans depends on two factors.  One is how cold it gets and how hard it freezes.  We won’t know the story on that until tomorrow.  The other factor is the growth stage the soybeans are at and that is determined by examining the pods on the plant.  It is all about the pods, so don’t get distracted by the condition of the leaves.  The more advanced/mature the soybeans pods are, the less the potential yield loss.

Manitoba Pulse and Soybean Growers has a maturity guide on their website that will provide you with excellent pictures and descriptions of the growth stages we are now seeing in our fields.  Use it as your guide in determining where your beans are at.  Click on the link below to access:

http://www.manitobapulse.ca/wp-content/uploads/2015/08/Soybean-MATURITY-GUIDE_Apr-2017_WR.pdf

In terms of yield loss, use the following as a guide:

  •  Frost during the R5 stage can reduce yield by 50%-70%.
  •  Frost at the R6 stage can reduce yield by 20%-30%.
  •  Frost at the R7 stage can reduce yield by only about 5%.
  •  At the R8 stage no yield reductions are expected. Dupont Pioneer has also put together a factsheet on frost damaged soybeans that is helpful  https://www.pioneer.com/home/site/us/agronomy/library/frost-damaged-soybeans/.

You will always find some variation around predictions of yield losses due to frost in soybeans.  This is to be expected.  There is no absolutely right answer.  No crop is uniformly at one growth stage and every frost event is unique in how it plays out.  The information above is merely meant to serve as a guide.

Let’s hope we stay well above zero!!

Submitted by: Terry Buss, Beausejour Farm Production Extension Specialist – Crops, MB Ag and Dennis Lange, Pulse Crop Specialist, MB Ag.

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What Would an Early September Frost Do to My Sunflowers?

September 5, 2017 – Risk of Frost in Pinawa, Winnipeg, Whiteshell and Steinbach tonight……….

Frost anytime before the sunflower crop reaches physiological maturity (R9) can cause damage. Once sunflowers reaches the R7 stage (ray petals have dropped, back of head starting to turn yellow), sunflower can withstand temperatures as low as -4° C, but temperature, duration and crop stage will influence the type and amount of damage.

A killing frost in sunflowers is considered to be -4 to -5° C for 6 or more hours, as this low temperature for the extended period is required to penetrate the thick layer in the back of the sunflower head and start the dry down process.  See attached bulletin for more details:

http://www.gov.mb.ca/agriculture/crops/production/pubs/frost-sunflowers.pdf

Visit www.canadasunflower.com for more updates on all sunflower issues

Visit Manitoba Agriculture http://www.gov.mb.ca/agriculture/crops/ for more frost information for other crop types

Submitted by Anastasia Kubinec, Manager – Crop Industry Development, Manitoba Agriculture

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6 Tips for Winter Wheat Seeding

Canola is coming off and seeding of winter wheat is upon us. While acres of winter wheat have dropped in recent years, there are good agronomic and economic reasons to include winter wheat in your crop rotation.  Get your winter wheat crop off to a great start this fall by considering these seeding tips.

  1. Stubble – Winter wheat needs a good snow cover of 4 inches or more to ensure winter survival. This can be accomplished by direct seeding into tall, dense standing stubble.   Stubble disturbance during harvest and seeding should be minimized to ensure that a good amount of stubble is retained for snow trapping.
  2. Weed control – It is important to control green cereal vegetation prior to seeding winter wheat to eliminate the risk of wheat streak mosaic virus. Winter wheat should not be seeded near immature spring cereals and all cereal volunteers should be controlled at least 2 weeks before seeding winter wheat.
  3. Variety selection – Yield is generally the first factor considered when choosing a winter wheat variety, but farmers should also compare varieties for agronomic factors such as standability, disease resistance, maturity, and winter hardiness. Seed Manitoba is an excellent starting place for evaluating the current and new varieties coming to the marketplace (www.seedmb.ca).
  4. Seeding date – Healthy, vigorous plants must be established before freeze-up to attain maximum cold tolerance. The goal is to have plants with a well-developed crown and about 3 leaves going into the winter. The crown is the area from which the plant regrows in the spring. Research has demonstrated that seeding during the period from late August to early September (approximately August 25 to September 10) consistently produces the best crops in terms of both yield and quality.
  5. Seeding depth – Winter wheat should be seeded less than 1” deep even when seedbeds are dry. Shallow seeding allows the seed to take advantage of fall rains, and as little as 1/3” of rain is enough to successfully establish winter wheat.
  6. Seeding rate – Seed at higher rates to ensure a dense, uniform plant stand to enhance weed competition, winter survival, and yield potential. Typically, farmers should be aiming for a final plant stand of 30 plants per square foot in the fall. Calculate the seeding rate needed to obtain the desired final plant stand with the formula below:

Seeding Rate (lb/ac) = Target plant stand/ft2 X 1000 kernel weight (g) / Expected seedling survival* X 10

*Expected seedling survival is used in its decimal form (90% = 0.9) and includes percent germination and seedling mortality.

 

 

Submitted by: Anne Kirk,  Cereal Crops Specialist, Manitoba Agriculture

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How to Obtain GOOD DATA from Strip Trials…..Use a Calibrated Yield Monitor…

In 2016, some of  John Heard’s corn nitrogen plots yielded over 200 bu/ac with the University of Manitoba plot combine.  He refused to report such astounding yields until the electronic weighing system had been verified with bagged and weighed yields. 

Likewise scrutiny and calibration is required when using yield monitors for strip trial tests.  In 2016 Manitoba Agriculture and Manitoba Wheat and Barley Growers Association compared harvest weights from strip trial yields in on-farm-tests looking at nitrogen and wheat protein.   Several farms had scaled grain carts in addition to their combine yield monitor (Figure 1) and all plots were measured with a weigh wagon.  Figures 2 and 3 shows the trends of grain cart and yield monitor data versus the weigh wagon yield (solid line).

Figure 1.  Comparing yield measuring systems – combine yield monitor, scaled grain cart and weigh wagon.

Farm A – with scaled grain cart used to calibrate yield monitor.  Yields follow trend of weigh wagon weights and are within 2 bu/ac.

Farm B – A seldom calibrated yield monitor with yields not corresponding to weigh wagon weights and up to 6 bu/ac less.
Yields from a perfectly calibrated yield monitor and grain cart would fall on the black line in the graphs above.  Farmers with accurate, scaled grain carts were usually calibrating their yield monitors in each field and producing very similar results as the weigh wagon (such as Farm A).  Those that were calibrated on earlier fields or earlier in the season were unable to measure the subtle yield differences in this study and may lead to erroneous conclusions.
So if yield monitors are being used to measure strip trial yields, I encourage growers to calibrate often with their scaled grain carts or a weigh wagon if available.  The measurements we made were in dry wheat but if crop strips are of varying moisture content, more frequent calibration may be warranted.
The study of the 8 farms comparing weighing systems is available at: http://www.mbwheatandbarley.ca/wp-content/uploads/2014/11/OFT-summary-2017-FINAL.pdf
Submitted by: John Heard, Manitoba Agriculture Crop Nutrition Specialist
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Do you Have Potassium Deficiency?

Several of our maturing crops are now exhibiting deficiency symptoms that are too late to correct, but important to address for next year.
Potassium (K) is often overlooked in much of Manitoba due to our naturally high K levels in clay and clay loam soils.  But deficiencies on lighter textured soils are increasing – particularly with soybeans. 

 

Picture 1: Mild potassium deficiency symptoms on upper leaves in August

Potassium deficiency often shows up during pod and seed fill, since soybeans remove 1.4 lb K2O/ bu of grain, the heaviest rate of removal of any grain crops.  As K is translocated out of leaves to fill seeds, the deficiency shows up as yellowing and later necrosis of the leaf margins.
Sometimes odd strips occur of alternating deficient and normal soybeans occur in fields.  These are often related to a previous canola or cereal swath that has had the K leach out of the swath into the soil beneath, and hence marginally increasing K supply in that strip.
If either of these symptoms are observed, a K deficiency can be readily identified with a traditional soil K test and a recommendation will be made for future K fertilization.

Picture 2: Alternating strips of varying potassium deficiency in maturing soybeans due to previous canola swaths.
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