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The Cropwalker - Volume 3 Issue 43

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Crop Conditions

Winter wheat generally looks quite good. Most fields of earliest planting have 2-3 visible tillers. Later planting may not have visible tillers but the heat last week will have initiated the cells that produce tillers. A few fields with weeds growing better than normal. Still time to spray, if current weather conditions stay above 5 C. Corn harvest is done on many farms and others just nicely started. Over the province probably 70-75% of the corn is off. Moistures finally dropped last week on some fields that were holding around 30%. Manure spreading occurred last week when it was dry on many acres. Nice to have manure storage as empty as possible this time of year.


Things to do this week

1.     Check winter wheat stands

2.    Last chance (maybe) for weed control.

3.    Review this year’s corn production. What could have been done better.

4.    Start to summarize results of plots.

Checking winter wheat stands

Check your stands. You like to have 20 plants per foot of row. Also check to see how uniform the stand is. Do all the plants have the same number of tillers. Should be 2-3 per plant. Also check to see if plants are evenly distributed. Do not want a clump of plants and then a space. Checking seeding depth, ideally 1 to 1.5” was the target. Check for trash in the trench. Perhaps the drill needs some maintenance for the 2021 spring planting season.  Finally check for weeds. If not spraying this fall you will have an idea for next spring. Winter wheat herbicides are selected based on winter annuals/perennials.

Still time for fall weed control

If you have perennial weeds like perennial sow thistle, dandelion and winter annuals like chickweed there is still an opportunity to control them (Refine M or Infinity/Infinity FX are good options). You can still spray winter wheat. There is an opportunity to spray corn stalks and soybean stubble with glyphosate. Glyphosate will work unless you get below -4    If it gets to this temperature weeds can start to regrow and give you an opportunity to control. Winter annuals and perennials are easier to control now than next spring. And some like perennial sow thistle need to sprayed 3-4 times to reduce the population.

Question Is it too late to plant cereal rye. Answer: It is a tad late, but cereal rye is more winter hardy than winter wheat. You may have enough soil moisture and heat to get it to germinate and grow if you plant immediately.

Corn Rootworm part 2

The story on this insect keeps unfolding. There are a couple of variants of this insect. Normally it lays its eggs at the base of corn plants. One variant has an “extended diapause” That is it lays its eggs and they do not hatch the next year but the eggs lay dormant until the following season. They hatch about 2 years after they are lain. So, if in a corn soybean corn rotation, they lay dormant until the field is back in corn. Another variant lays its eggs in soybean fields. Then when corn is planted there the eggs hatch and the larva damage the corn roots. Paul Sullivan CCA in Eastern Ontario along with another agronomist in that area had about 10 fields this year where there was significant corn rootworm feeing damage and the fields were not in corn last year. They suspect this is one or other of the variants. Right now, there are no known fields that suffered rootworm damage when the previous crop was wheat.

Nematodes control rootworm larva

There are some reports of a certain nematode when added to the soil destroys rootworm larva. When you read the reports, they sound gruesome and unbelievable. They talk about the nematodes invading a rootworm larva, multiplying and “coming out like a greenish yellow mass” These are supposedly more nematodes that will go to kill more rootworm larva. These nematodes are being tested in the US and we will keep you informed. (I find the reports to be unbelievable).

What rotation is best for building soils?

I have spent a few hours gathering info. Not a lot that is pertinent to Ontario. There is one research trial that Dr Terry Daynard University of Guelph started about 37 years ago and the trial is being carried on. Bottom line is that continuous corn does not appear to be building organic matter. (There is a difference between crop residue and organic matter.) Researchers have agreed that the best way to measure soil improvements is to measure Soil Organic Carbon (SOC) rather than measure organic matter.  So, the research list below suggests that in the top 6” of soil, alfalfa and corn are the best ways to build SOC. Dr Bill Deen is retired but he graciously spoke to me. His summary was “the more crops you have in rotation the more likely you are to build soil organic matter. As measured by SOC.  The rotations are CCCC continuous corn, CCSS corn corn soybeans soybeans, CCSW is corn corn soybeans wheat, CCAA is corn corn alfalfa alfalfa, AAAA is continuous alfalfa.

There are still a lot of unanswered questions. 1) Is organic matter in the deeper soil profile increased more with forages. 2) If OM in a field is below fence row levels can you build it faster with continuous corn or forages. 3) Research was done with lower corn yields than we are now experiencing.

This topic intrigues me so you will see more. (Following is one summary on this topic.

Fig 1.  SOC stocks in 20-cm fixed soil depth (A) compared with SOC stocks in an equivalent soil mass of 238 kg m-2 (B) as affected by crop rotation diversity and perenniality (re-drawn using data from Table 1 above)

Figure 1 - Effect of Crop Rotation on Soil Organic Carbon

'Data from King et al. (2020) and Meyer-Aurich et al. (2006) - re-analyzed by Susantha Jayasundara, University of Guelph'

One of the papers can be reached here, before warned, content is dry reading

Long-term tillage and crop rotation effects on soil quality, organic carbon, and total nitrogen Laura L. Van Eerd1 , Katelyn A. Congreves1 , Adam Hayes2 , Anne Verhallen2 , and David C. Hooker3

Doing a Corn Post-Mortem

Have received a couple of phone calls from producers frustrated with what should be exceptional corn yields given the growing conditions. Much of it seems to be related to planting into cold soil conditions and simply not having enough plants to make up the yield you expect in some of these areas. I did note in the spring that we should be backing off yield potential in some areas due to higher than normal seed mortality (mainly due to seed chilling/imbibition). Even though a few areas within the province had expectational rainfall and sunlight during the grain fill period there simply wasn’t enough ears to fill to make it an exceptional crop. Instead it’s an average to slight above average crop.

If you want do some more digging into final yields and whether populations or another factor is the reason for the end result, use John Deere operations centre or Climate Fieldview to go and inspect those areas. Even though the crop is off, counting stalks can provide a rough estimate on the number of ears (stalk size can be an indicator of ear size due to later emergence, skip the runts). Cobs can be inspected to determine approximate ear size, if there was an issue such as nitrogen deficiency, there may be small kernels still on the tip of the cob. Lastly check to see how much corn is on the ground, 2 kernels per square foot equals 1 bushel/ac of harvest losses. Still unsure after all of this? Start digging up root balls to determine if compaction or smeared seed trenches lead to issues. While not a slam dunk, a post-harvest investigation can provide a few ideas on possible causes for a less than desirable corn yield.

Picture 1 - Corn Roots can Provide Some Clues on Hybrid Performance
Picture 2 - Soil Compaction can still be evident
Picture 3 - Check for loss kernels on soil and cobs for Harvest Losses
Picture 4 - Check for small kernels on cob tips

Tale of Two Corn Plots.

One corn plot was posted on Twitter with a difference in planting dates by Jeff Steiner of Reesor’s Seed and Grain, this plot was done in the Elmira, ON area on a few different dates at various soil temperatures. Bottom line is that if you choose to plant in cold ground conditions because the seed bed is fit, bump up your population to account for seed mortality.

Figure 2 - Corn Planting Date and Harvest Stand/Yields

Another plot was planted in the same window as Elmira plot (May 6th), but the biggest factor in determining if you had strong yields was hybrid flowering date. And another factor. It may not stick out until doing some rough math on the spacing interval between the hybrid winners. See below. I’ve followed this retailer’s plot location for several years, simply because it has such a wide range of genetics and maturities in one location, and they have a co-operator that thorough enjoys putting the plot in. Consistently the shorter day maturities in the plot struggle to be a winner, I question why growers in that area would even consider them, yes the odd year the top end yield will be nipped off due to an early frost (which would have occurred to some extent in the plot below), but in most situations the yield hit is still less than what you would have given up if you had grown earlier day hybrids over a 5 year period.

Figure 3 - Corn Plot Data
Figure 4 - Corn Plot Data sorted by Yield (top 10/bottom 10 hybrids highlited)
Figure 5 - Corn Yield Sorted by Population
Figure 6 - Corn Plot Sorted by Heat Units (Blanks/? = Experimental Hybrids)
Figure 7 - Chart of Hybrids by Entry vs Dry Yield in Bushels
Figure 8 - Chart of Hybrids by feet from Plot Edge vs Dry Yield in Bushels
Figure 9 - Yield vs Feet from Plot Edge (red = 90' centers, blue = overlap areas)

Now that you have seen all the plot info, there could be a strong effect from an in-crop fertilizer application. Assuming 90’ spread with. Regardless, producers in that area should be corn maturities to 2750 to 2850 CHU for first planted corn.

“Test counterintuitive things only because no one else will.”

- Rory Sutherland