Effect of Spring Frost on Emerging Crops

Submitted by Anastasia Kubinec, Manitoba Agriculture

Originally posted May 8th and 30th, 2015…..re-post May 13, 2016 and now May 27, 2019.

Don’t assume because there is frost (or snow) on the ground, that your emerging crop in dead!

With the drop in temperatures in the past couple of days, there are a few things to keep in mind if the mercury dips below 0°C. The temperature is the instigator for causing frost, but whether it is -0.1°C or -4°C the damage inflicted is highly influenced on these other factors:

  1. Duration
    • Short frost = < 2 hours,  may not cause much damage if frost is light (above -1 to -2°C), crop type and staging is tolerant, conditions wet and crop has become acclimatized.
    • Short frost = < 2 hours, but hard frost (lower than -2°C), crops like canola are more sensitive to longer frost vs. cereals, damage can be variable in field and across area.
    • Long frost = > 2 hours, whether frost is light or hard the longer the negative temperatures the more time for damage to happen.  Tolerance by crop type varies.
  2. Other Environmental Conditions
    • Cloudy and wet – prior to a frost, cool temperatures slow plant growth and ‘hardens’ plants off, which will help them tolerate a frost.  Also wet soil helps buffer the cold air effects on the plants, as wet soils change temperature slower than dry soils.
    • Sunny and dry – The combination of a  dramatic drop in air temperatures when plants are actively growing then a brilliant sunny day after the frost event is where we have seen the most damage.  Scouting after the frost (24 and 48 hours) is very important though to assess extent and percentage of field injury.
    • Field trash cover – increased trash in fields was seen to increase frost damage on very susceptible crops in the 2009 June frost
  3. Crop Type
    • Spring Cereals – more tolerant than other crops types, can tolerant to temperatures as low as -6°C as growing point below ground until the 5 leaf stage.
    • Winter Wheat – can withstand very low temperatures for a short period of time (-11°C for less than 2 hours) up until the tillering stage.
    • Corn – smaller then V5, will recover from light frost as growing point below ground. Leaves probably will be killed, but plants will recover if the growing point ok.
    • Oilseeds – environmental conditions impact frost severity on susceptible canola and flax cotyledons. Resiliency increases at the 3-4 leaf stage (canola) or 2nd whorl (flax).  Sunflowers are fairly tolerant  up to the V4 stage.
    • Pulses – peas are most tolerant, then soybean, edibles bean are very susceptible even before emergence.   Field pea crops are rarely lost to frost. Soybean are more sensitive, but the smaller the soybean plant the more tolerant they are  – from emergence to cotyledon can withstand short light frosts.

Scouting After a Frost

Scouting should start 24 – 48 hours after the frost and continue for the 5 days following the frost event.  Look for leaves wilting, looking “water-soaked” or see “frost banding”.  Watch for new growth in the plant.  You do not want to see plants wilted and not perking back up or pinching off on the stem near the growing point (canola, flax, soybeans).  Also assess the area affected by frost, small areas or a few plants damaged are ok, as other plants emerged (or just emerging) will fill in those spaces.  Large dead areas may need to be re-seeded.

If in doubt of what look for, call your local agronomists, local FPE Specialist with Manitoba Agriculture or the Crop Industry Branch.

For more specific details on what actually occurs to plants with a frost and crop specific details and symptoms to look for (and how long after a frost to do assessment) see Manitoba Agriculture’s Spring Frost Damage Bulletin.

 

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Managing Winter Killed Hay and Pasture Fields

Severe winter weather can cause increased winter kill of forage stands in Manitoba. Alfalfa is prone to winterkill if the crown (the point on the plant from which all the stems grow from) is oxygen deprived due to ice cover, or if it freezes to -12 C or colder for 2-3 days.

If it is decided that a stand is sufficiently compromised that renovation is needed, some factors need to be considered. Alfalfa plants produce toxins (called medicarpins in the leaves) that reduce the germination and growth of new alfalfa seedlings.  Older stands have produced medicarpins longer and therefore have more of a build up or concentration in the soil around the plant where the leaves drop to in the fall of the year.  Generally the medicarpins are within 16” of the crown, so reseeding or over seeding alfalfa into these areas results in limited success.

Medicarpins break down over time, so a break from alfalfa for a year is sufficient time to allow for successful re-establish of alfalfa on that field.

Sod or no-till seeding can be a successful way of renovating old stands so long as the above information has been considered. These are some tips for successful germination and emergence of sod seeded forages.

  • Soil test and apply fertilizer as required, especially phosphorus (P).
  • Suppress competition from the existing vegetation, especially under drier soil conditions. 1.5 l/acre glyphosate (480 g/l formulation) will suppress the vegetation for about 60 days.
  • Use seeding equipment appropriate for sod seeding conditions.
  • Packing (in furrow or land roller) will slow drying of the soil and allow seeds to imbibe water more easily.
  • Plant shallow, i.e. ¾ inch or less. Small seeds do not have enough energy in the seed to emerge from deep plantings.
  • Check seeding depth and packing regularly while seeding.

 

If you have more questions or concerns please contact:

 

 

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How Can I Reduce Fertilizer Losses in Dry Spring Soils?

Dry spring weather is great for seeding but may play havoc with some fertilizer applications and losses.

1.Seedplaced fertilizer – Where seedbed moisture is low or when weather is hot and windy, reduce the rates of seedplaced nitrogen  by approximately 50 per cent. Table 7 of the Manitoba Soil Fertility Guide  http://www.gov.mb.ca/agriculture/crops/soil-fertility/soil-fertility-guide/nitrogen.html indicates safe rates of seedplaced urea under different soil texture, moisture and seedbed utilization conditions.  But as conditions dry, these rates should be reduced accordingly.

2.Surface applied urea or urea-forms (like UAN solution 28-0-0) – are vulnerable to volatilization losses.  The soil and environmental factors increasing risk of loss are well known and include:moist soil conditions, followed by rapid drying

  • high wind velocity
  • warm soil temperatures
  • high soil pH (> pH 7.5)
  • high lime content in surface soil
  • coarse soil texture (sandy)
  • low organic matter content
  • high amount of surface residue (Zero Till)

Volatilization losses can be reduced with dribble placement of UAN versus broadcast applications and the use of an urease inhibitor.  The active ingredient NBPT used in Agrotain Ultra is now marketed by a number of companies.  To expect the same level of protection as Agrotain Ultra, ensure the application rate is similar, since formulation strength and recommended rates differ among suppliers.  Agrotain Ultra contains 27% NBPT with an application rate of 3.1 l/tonne urea or 1.6 l/tonne UAN.

3. Last year the lack of rainfall through much of May left surface applied nitrogen stranded at the surface.  If possible, a portion of the crops nitrogen for cereals and canola should be in-soil placed.  In season applications should be targeted prior to stem elongation of cereals and bolting of canola.

 

 

 

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Manitoba Ag Weather Network

Manitoba Agriculture has a number of weather stations across the province that measure air/soil temperature, soil moisture, wind direction and speed.  For local information please visit

Central/East/Interlake Regions: http://www.gov.mb.ca/agriculture/weather/current-conditions-summary1.html

Southwest/Northwest Regions: http://www.gov.mb.ca/agriculture/weather/current-conditions-summary2.html

Previous Day on Highs/Lows and Average Soil Temperature at:

Central/Easter/Interlake:http://www.gov.mb.ca/agriculture/weather/yesterdays-summary1.html  Southwest/Northwest: http://www.gov.mb.ca/agriculture/weather/yesterdays-summary2.html

Another useful application of the data gathered by the network for rainfall can be found at Rain Watch http://www.gov.mb.ca/agriculture/weather/rain-watch.html

 

 

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Seeding for Target Plant Stands, not lbs/ac

Seed can be an expensive input, but a poor crop stand can be lost profit.  To maximize your seed, still get the stand needed to optimize yield, start calculating the real seeding rate needed for the plant stand desired and not gauging seeding rate by lbs/ac or bu/ac.

The following are the standard recommendations for FINAL plant stand, not what you are putting in the ground. Germination, TKW and mortality are very important to use in the equation to determine actual seeds/ac to plant.  For example, if you assume your germination is 96% and its only 85% and conditions turn cold and wet (increasing mortality), you may have a lot thinner stand than you anticipated (which could mean a harder time controlling weeds).

                    Grain Crops                               Oilseed Crops                   Pulse Crops        
Barley Wheat Oat Corn Canola Sunflower Flax Peas Soybean Dry Bean*
Plants/ft2 22-25 23-28 18-23 7-14 37-56 7-9
 Plants/ac (1000s) 26-30 18-22 180-210 85-100
Mortality Rates (%) 10-15 10-15 10-15 10-15 20-60 10 40-50 5-15 5-10 5-10

*Navy Bean = pinto beans on lower end and navy bean require higher plant stands

Source:  Manitoba Agriculture, Canola Council of Canada, Flax Council of Canada, Ontario Ministry of Agriculture, Food and Rural Affairs

 Seeding Rate (lbs/ac) = target plant stand/ft2 x TKW (g) / % expected seed survival x 10                       

 e.g. FLAX Seeding Rate= 45 plants/ft2 x  5g (TKW) / ((88% germination x (1- 40% mortality)) X 10 = 43 lbs/ac

Other information

Wheat – http://www.gov.mb.ca/agriculture/crops/production/print,aiming-for-higher-wheat-yields.html

Using 1000 Kernel Weight for Calculating Seeding Rates – http://www1.agric.gov.ab.ca/%24department/deptdocs.nsf/all/agdex81

Canola – http://www.canolacouncil.org/canola-encyclopedia/crop-establishment/seeding-rate/

Optimizing Plant Establishment – http://www.gov.mb.ca/agriculture/crops/production/pubs/optimizing-stand-establishment-in-less-than-optimal-conditions.pdf

 

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Seed Placed Fertilizer – Safe Rates

A reminder that if seedbeds turn dry, the safety margin shrinks when applying seed placed fertilizer.  Seedburn can result from ammonia toxicity and/or salt content of fertilizers.

For nitrogen, our Soil Fertility Guide provided safe guidelines for seed placed urea on cereals and canola across a range of soil types and seed-fertilizer configurations.  With the increased popularity of narrow seed and fertilizer spreads with disk drills, the safe rates are reduced.  For example, safe urea rates for cereals vary from 10 to 25 lb N/ac going from sand to clay soil using disk openers on 6” row spacing.  These guidelines are for moist soil and should be reduced by 50% if seedbed moisture is lower when weather is hot and windy.

The safe rates of seed placed phosphorus depends on the crop, with cereals being quite tolerant compared to soybeans, dry beans and canola.  With a disk drill as described above, cereals can tolerate 50 to 60 lb P2O5/ac as mono ammonium phosphate while rates would be 20 lbs/ac for canola and less for beans.   If there greater seedbed utilization (i.e. narrower rows or a wider seedrow with less fertilizer concentration) rates could be more liberal.

More on these safe rates of fertilizer is posted on Manitoba Agriculture’s website at: http://www.gov.mb.ca/agriculture/crops/soil-fertility/print,safe-rates-of-seed-placed-phosphorus-for-manitoba–narrow-row-and-row-crops.html

 

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Spring Frost or Late Snow and Emerged Canola – Time to Re-Seed?

Temperature is the instigator for causing frost, but damage inflicted and need to re-seed canola is highly influenced on these other factors:

  1. Duration
    • Short but LIGHT frost = < 2 hours,  may not cause much damage if frost is light (above -1 to -2°C), crop type and staging is tolerant, conditions wet and crop has become acclimatized.
    • Short and HARD frost = < 2 hours, but hard frost (lower than -2°C), crops like canola are more sensitive to longer frost vs. cereals, damage can be variable in field and across area.
    • Long frost = > 2 hours, whether light or hard the longer the negative temperatures the more time for damage to happen.  Tolerance by crop type varies.
  2. Other Environmental Conditions
    • Cloudy and wet – prior to a frost, cool temperatures slow plant growth and ‘hardens’ plants off, which will help them tolerate a frost.  Also wet soil helps buffer the cold air effects on the plants, as wet soils change temperature slower than dry soils.
    • Sunny and dry – The combination of a  dramatic drop in air temperatures when plants are actively growing then a brilliant sunny day after the frost event is where we have seen the most damage.  Scouting after the frost (24 and 48 hours) is very important though to assess extent and percentage of field injury.
    • Field trash cover – increased trash in fields was seen to increase frost damage on very susceptible crops in the 2009 June and May 30, 2015 frost
  3. Crop Type
    • Spring Cereals – more tolerant than other crops types, can tolerant to temperatures as low as -6°C as growing point below ground until the 5 leaf stage.
    • Winter Wheat – can withstand very low temperatures for a short period of time (-11°C for less than 2 hours) up until the tillering stage.
    • Corn – smaller then V5, will recover from light frost as growing point below ground. Leaves probably will be killed, but plants will recover if the growing point ok.
    • Oilseeds – environmental conditions impact frost severity on susceptible canola and flax cotyledons. Resiliency increases at the 3-4 leaf stage (canola) or 2nd whorl (flax).  Sunflowers are fairly tolerant  up to the V4 stage.
    • Pulses – peas are most tolerant, then soybean, edibles bean are very susceptible even before emergence.   Field pea crops are rarely lost to frost. Soybean are more sensitive, but the smaller the soybean plant the more tolerant they are  – from emergence to cotyledon can withstand short light frosts.

Scouting After a Frost (or Snow event)

Scouting should start 24 – 48 hours after the frost and continue for the 5 days following the frost event.  Look for leaves wilting, looking “water-soaked” or see “frost banding”.  Watch for new growth in the plant.  You do not want to see plants wilted and not perking back up or pinching off on the stem near the growing point (canola, flax, soybeans).  Also assess the area affected by frost, small areas or a few plants damaged are ok, as other plants emerged (or just emerging) will fill in those spaces.  Large dead areas may need to be re-seeded.

If in doubt of what look for, call your local agronomists, local FPE Specialist with Manitoba Agriculture or the Crop Industry Branch.

For more specific details on what actually occurs to plants with a frost and crop specific details and symptoms to look for (and how long after a frost to do assessment) see Manitoba Agriculture’s Spring Frost Damage Bulletin.

NEW RE-SEED Calculator developed by Manitoba Agriculture using historic data from MASC is another tool to help determine if re-seeding is finanacially the right decision, depending on plant stands and time of year see calculator at: https://www.gov.mb.ca/agriculture/business-and-economics/financial-management/pubs/calculator_canolareseed.xls

Submitted by Anastasia Kubinec, Manitoba Agriculture, Oilseeds Crop Specialist

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Soil Fumigants and Licensing for Application

Soil fumigants are pesticides that form a gas when applied to soil. Due to the toxicity of soil fumigants and the potential for gases to move from the soil to the air, soil fumigants are classified as restricted use pesticides.

Requirements for the use of soil fumigants include:
  • Soil fumigation license
  • A Fumigation Management Plan (FMP) for all soil fumigation applications
  • Mandatory Good Agricultural Practices (GAPs)
  • Notification of Application
  • Restrictions for workers re-entering treated areas
  • Buffer zones

Steps to obtaining a soil fumigation licence:

  1. Complete the Application for Pesticide Certification
  2. Write the exam
  3. Obtain general liability and pesticide drift insurance
  4. Apply for a licence

For more information on soil fumigation certification and licensing see http://www.gov.mb.ca/agriculture/crops/seasonal-reports/current-crop-topics.html#horticulture and/or contact:

Anne Kirk, Pesticide Minor Use and Regulatory, Manitoba Agriculture
Phone: (204) 745-5663 , Email: [email protected]


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QU: Should I Be Worried About Stored Canola and Flax Spoiling on a 31C Day in May

Excellent question that we usually do not have to think about in early May!

As most grain is still cold in the bin and with the rapid increase in outside temperature, the potential for spoilage could still occur in stored canola and flax still in the bin from 2015 harvest.

If you think this might be an issues, check what is the seed moisture and the temperature is again. The 5C, 8.5% moisture canola in March had no risk of spoilage, but a 35C, 8.5% moisture canola does.  Flax is susceptible to spoilage as well, if the grain gets very warm in the bin and the moisture is over 8%.   If things are all good today, check in a couple of days again if the May heat wave continues and consider turning on the aeration fan and open up the bin hatch at the top of the bin to let humidity escape.

This question came in as a concern over the potential of condensation to form on the bin walls from the hot outside air hitting the cold grain in the bin.  Aeration could be used as a tool with the hot, but very dry air to warm the grain slowly and move some of the potential humidity out through the top vent or hatch.  Monitoring though is key and should continue until the grain is delivered to catch spoilage issues. A great resource on more about aeration and grain in storage can be found on the PAMI (Prairie Agricultural Machinery Institute) website www.pami.ca/crops/storage and at the Canadian Grains Commission https://www.grainscanada.gc.ca/storage-entrepose/ssg-de-eng.htm

Safe storage chart for canola and flax

Submitted by Anastasia Kubinec, Oilseed Crop Specialist, Manitoba Agriculture

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Fall Fertilizer Decisions Based on Soil Temperatures

 

 

Growers should be monitoring soil temperatures to guide fall nitrogen management.  Provincial weather station soil temperatures are posted at: http://www.gov.mb.ca/agriculture/weather/soil-temperature.html

The principle of fall fertilization is generally to delay applications until soils have cooled so microbial activity is curtailed.  That way less of the stable ammonium form-N (NH4+,) that is held on clay and OM, is converted to nitrate (NO3-) which can leach or denitrify.

The rate of nitrification of banded N to nitrate is illustrated in the following table from http://www.gov.mb.ca/agriculture/crops/soil-fertility/a-fall-fertilization-refresher.html

 

Table 1. Nitrification rates of ammonia to nitrate form-N from banded urea (calculated from Tiessen et al, 20031).

Average soil temperature at band depth Days for 50% conversion to nitrate Days for 100% conversion to nitrate
1 oC

5 oC

10 oC

15 oC

20 oC

190

40

20

13

10

380

80

40

25

20

 

So as soils cool and eventually freeze, the microbial activity is reduced such that ammonium-N is retained in its stable form.  If one chooses to apply nitrogen before Mother Nature provides cool soil – they may consider using one of several enhanced efficiency fertilizers – N-Serve, eNtrench, ESN or SuperU. 

Submitted by: John Heard, Soil Fertility Specialist

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