8 min read

The Cropwalker - Volume 2 Issue 39

Always read and follow label directions.

October 2019 Complimentary Issue; to become a member and receive all issues, sign up at:


After becoming a member, you can view past members only issues at newsletter.fieldwalker.ca, plus any future issues will be emailed directly to your inbox.

Crop Conditions

Weather - Temperatures dropped below freezing in parts of Ontario. Overall minimal effect on crops. Many areas had “frost on the roof but crops appear to be okay”. We won’t know full extent for a few more days, but looks like affect was minimal. It looks like the weather will allow a lot of soybeans acres to be harvested this week. Winter Wheat-  Seeding will continue this week as soybeans come off. Keep seeding rate at 1.6-1.8 M seeds/ac. Keep seeding depth at 1-1.25”. Check often. Some reports of wheat being seeded shallower than what was intended. Soybeans Many areas still at only 5% of beans off. Some areas 25% or more off. Yields of this 5% off are below average. Some reports of green beans. If you cut through the bean and it is just the outside that is green, they will turn colour once harvested. If they are green all the way through, that is not good. Corn - silage harvest is progressing quickly. Please be safe in regard to silo gas, in Ontario each year, we lose people to silo gas.


What Happens When a Frost Event Occurs?

Frost occurs happens when cold air around plants gets below freezing. This typically happens on a clear night, when there is no cloud cover to trap the earth’s warm air. The ground is giving off warm air, and, cold air comes down and mixes with this warm air. It is not uncommon to have frost on the roof, but not damage crops. This is because the car roof is not giving off heat. Cool air flows like water, so that colder pockets will be in lower areas. However, high areas may be drier, not holding as much heat, and can be frozen. It is not uncommon if the air temperature dips to -1, to have tops of corn plants frozen, but the lower parts of the plant are not. If this occurs, the corn plant will continue to move nutrients to the ear. The wet weather the past few days meant there was more heat in the ground than if the weather was dry.

Rules of Thumb for Spraying After a Frost

It depends on a few factors; weeds species, weed size, herbicide used and how cold/length of the frost event. If you have a hard frost, in most situations you would not have to worry about trying to control annual grass and broad-leaves, mother nature has done this for you. In this situation, we will focus on biennial, perennial, and winter annual weeds.

Glyphosate is most effective when applied at air temperatures at 16-24’C for a few hours following application. Glyphosate can still be effective at temperatures of 8-10’C; but will have slower herbicide uptake and translocation. This increases the rain fast period and slows down the onset of symptoms. Growth hormones such as 2,4-D ester or dicamba are less impacted by lower temperatures.

Table 1 - When to spray following a frost event

For best control, avoid a frost following application for; 24 hours on annuals, and 72 hours on perennials, and spray during bright sunshine.

(Notes from Clark Brenzil, PAg, Saskatchewan Provincial Specialist Weed Control; Roundup Technical Bulletin)

Seed Wheat or Spray First

Once the soybeans are off seed wheat ASAP. If you did not use a pre-harvest, try and get Roundup on before wheat emerges. You should have 3-4 days between seeding and wheat emergence (provided the seed trench is closed).

Wheat Planting Depth

I was asked what rate I recommend growers seed their wheat at. My comment was, deep enough to cut the trash, and, close the seed trench, but not less than 1-1.25”. I have seen too many wheat fields get ripped up in the spring because of either shallow seeding, and/or open trenches. Majority of wheat should emerge within in a 1-3 day window for maximum yields (similar to corn).

Weed Seeds in Manure

Some of the “new weeds” are being introduced in livestock feed. This begs the question, does ingestion, ensiling, or composting get rid of the weed seeds? A lot of researchers have looked into this. The short answer is no. Feeding weeds seeds reduces the viability. Viability of weed seeds is reduced more in poultry, than in cattle or pigs. Ensiling also reduces viability. Composting manure can reduce viability if the temperature is hot enough, for a long enough time. You need temperatures between 140-170 o F for a number of hours. The % viability varies with temperature, length of heat, and weed species, but all of these systems still can leave 2-10% of weeds seeds being viable.  A survey of fresh dairy manure in New York found an average of 75,000 viable seeds per ton, and a range of 0 to 400,000 seeds. A 2% survival of 75,000 would leave 1,500 viable seeds remaining per ton. Applied at 8 tons per acre, that would increase the weed seedbank by 12,000 seeds per acre. Solution?  c Constantly watch fields for new weeds. They may come in feed/bedding or from your neighbour, or blow in on the wind.

Sorghum and Sorghum/Sudan Grass After a Frost.

Notes from OMAFRA

  • Don't graze plants
  • during or immediately after a drought, or under conditions where growth has been reduced
  • on nights when a frost is likely, high levels of the toxic compounds are produced within hours after a frost occurs
  • after a killing frost, until the plant is dry and brown, as cyanogenic glucosides usually dissipate within 7 days.
  • after a non-killing frost until regrowth is at least 45 cm (18 inches) tall
  • Don't green chop or ensile the forage for 3 to 5 days after a killing frost.
  • Allow forage to ensile for at least 3 weeks before feeding.

Most cattle poisonings from frosted sorghum are caused when cattle graze frosted sorghum. The other issue is if cattle are fed frosted sorghum, the effects may be reduced by feeding other feed stuffs.

Silo Gas Review

A variety of gases are formed in conventional or open-top silos with nitrogen dioxide being the most abundant. This highly toxic gas is characterized by a strong bleach-like odor and low lying yellow, red, or dark brown fumes. Unlike carbon dioxide, nitrogen dioxide levels reach a peak about three days after harvesting, and rapidly begin to decrease thereafter, particularly if the silo is ventilated. The gas actually starts forming within hours of the material being ensiled. After two weeks it is unlikely that more gas will be produced, although some hazard remains if the gas has not been able to escape the silo.

Nitrogen Dioxide is harmful because it causes severe irritation to the nose and throat and may lead to inflammation of the lungs. However, what makes this gas especially dangerous is that low level exposure to it is accompanied by only a little immediate pain or discomfort, though death can and has occurred immediately after contact with high concentrations. A person might breathe the gas without noticing any serious ill effects, and then die in their sleep hours later from fluid collecting in their lungs. Many victims can suffer relapses, with symptoms similar to pneumonia two to six weeks after the initial exposure. For these reasons it is extremely important for anyone who is exposed to this gas, even a short time, to seek immediate medical attention.

Like carbon dioxide, nitrogen dioxide is heavier than air. Because of this, as it is produced, it tends to settle right on top of the silage, or flow down the silo chute and collect in the adjoining feed rooms, or other low lying areas near the base of the silo.

Gas may even flow into the barn itself and become trapped in corners, under feed bunks, or lie low against the floor. The threat that this poses to livestock is a serious one. (Notes from Farm Safety)

Spreading Magnesium in the Fall

There are some nutrients that can leach if fall applied. The least apt to leach is P. The most apt to leach is N. Other nutrients such as K are intermediate. On lighter soils with a CEC of 10 or less K can leach. The distance it leaches depends on subsoil characteristics. Heavy subsoil has less leaching than light. Magnesium is somewhat similar to K. On soils with a low CEC say 5-8 Mg can leach, especially if K levels are high. There are only so many sites for Mg to bind. K has first choice at some of these sites. So, if CEC is low and K is high, there is more of a chance of Mg leaching, and thus low rates of Mg should be spring applied.

GPS System Segments

I was recently in the market for a GPS unit, this is what I found;

1)    Most manufacturers make three levels of displays/field computers;

Entry level – Steering Only

Will provide lightbar or steering control, and some models offer as applied maps, typically a smaller screen. Examples; Ag Leader Compass, Outback S-lite, Topcon X14, Trimble 250, etc. Most will not have ISOBUS capability.

Mid-level – Steering/Simple Machine Control

Will provide steering control (either through hydraulics or after-market attachments), as applied maps, with limited machine control, such as; running a sprayer, fertilizer spreader, drill etc. May have ISOBUS capability, allowing the control of a spreader/sprayer/baler, etc. without requiring an additional monitor. Examples; Ag Leader InCommand 800, John Deere 4200/4240, Outback Rebel, Raven CR7, Topcon X25, Trimble CFX750.

Do it all-level– Steering/Machine Control/Data Management

Will provide steering, record harvest data, operate a planter and record the data, run a tile plough, etc, plus all the capabilities of the other monitors. Examples; Ag Leader InCommand 1200, Case IH Pro 700, John Deere 2630/4600/4640, New Holland IntelliviewIV, Raven Viper4, Topcon X35, Trimble TMX-2050.

2)    Manufacturers also have different receivers, depending on the accuracy of the signal required, the receivers can be broken into two groups;

WAAS/Entry-level Correction

Suitable for tillage and other low accuracy tasks, may or may not work with auto steer (6-8” accuracy). Examples; Ag Leader 6000, Raven 500s, Topcon SGR1, Trimble 162.


Will have WAAS as a starting point, then you can subscribe for more accurate steering control (2-6” accuracy) or add radios for RTK correction (<1” accuracy). Ag Leader 7500, John Deere Starfire 3000, Outback A222, Raven RS1/600s, Topcon AGI-4, Trimble 372.

What about units like Precision Planting’s 20/20 monitor? While highly sophisticated and growers like many of its features, it does not offer any steering capability, and is purely a planter/side-dress bar/combine monitor, it also does not offer ISOBUS capabilities.

Considering one not listed here? It might be resold under a different name, or a non-current model. The list is a guide and is not exhaustive of everything available on the market.

Do You Have A Significant Increase in Soil Test Values?

I have a soil test back where the phosphorous levels changed from 20 to 30 on the sodium bicarbonate (Olsen) test. This change suggests that 350 pounds of phosphorous was applied above crop removal and did not get used. Of course, over the 3 years between the test we didn’t apply that much. And there would be no accounting for removal. So, what’s going on. Number of things. Soil analysis is not as accurate as say your thermometer. Soil tests are one indicator of what is going on. You need to use soil test levels along with application history and removal rates (yields) There is a 25% variation in soil analysis. So, if the first test was low by 25% and the second test high by 25% this explains a lot. Other reasons for variation are soil sampling depth. If soil was drier this year and sample was shallower than last time the results will vary. And the person taking the sample makes a difference. I like to have the soil sampler take a lot of samples. And send the samples to the same lab. There is a difference between labs, even when using the same extractant. Another factor is if the soil cores are pulled from the same areas every time, if more cores are pulled from an eroded knoll one time, and more cores are pulled from an area that has a depression the next time, you will get different results.  Soil sampling is just one tool to use, it is more like a yard stick, than a caliper.

If you wait until you're ready, you'll be waiting the rest of your life.” – Shane Parrish