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The Cropwalker - Volume 4 Issue 6

Always read and follow label directions.

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Question I have been using the same corn herbicide for a few years. Should I switch?

Answer: In this case the grower has a three-crop rotation of corn soybeans wheat. Weed control is good. I suggested no big reason to switch since he has great weed control. You don’t want to be using the same group of herbicides year after year. In this case he is using different groups in each crop. The one caution is to watch for new weeds. Water hemp is spread by migrating birds. Fleabane is spread by wind. Combines spread numerous weeds. Your neighbours may not be as diligent as you are, so you must watch what weed escapes your neighbour has and take action. Just because there are products with different names, for example Primextra on corn vs Boundary on soys, doesn’t mean you are using different modes of action, both have group 5 (Atrazine vs. Metribuzin) and group 15 herbicides (Dual).

Question I have a bindweed problem in some fields. What is a good strategy to get rid of it?

Answer You can eradicate bindweed. Weeds like lambs’ quarters and ragweed, you will have for years. Bindweed has an extensive root system. This root system has numerous nodes that will initiate new growth. Many of these nodes will lay dormant if there are other ones growing. So, you have to hit this weed several times to deplete all of these nodes. And you have to spray when bindweed is translocating nutrients to the roots. If you spray at other times it is just like hoeing the weed. You take off the top, but the root is still there. Bindweed is translocating to the root around flowering time. This occurs in wheat fields in mid to late September. In corn and soybean fields it CAN occur late June. If you spray with glyphosate in mid to late May, you will burn the top off and the plant starts to grow. It will not come into flower until mid-July. Too late to spray. So, in corn a strategy is to put down an herbicide that will get you to mid-June and spray glyphosate just before the rows close say at 6-8 leaf. At this stage, spray as high a rate as possible. If you really want to get rid of it then you may have a second chance post corn harvest apply another spray. Logically this field would go to soybeans the next year. Then again use a good preprogram and spray bindweed late June. Follow this up with a pre harvest spray.

Comparing Xtend and Enlist Soybean programs (taken from an article by Dwight Lingenfelter Extension Associate Weed Scientist at Penn State University) Check Ontario labels for specifics but there are some commonalities between what is being practiced in PA and ON, we have shortened the table for specifics.

Currently, in Pennsylvania Xtendimax, Engenia, and Tavium are the only dicamba-containing products that can be used in Xtend or XtendFlex soybeans. Refer to these websites for additional information and updates: In the Enlist E3 platform, Enlist One and Enlist Duo are the only 2,4-D-containing products that can be sprayed in Pennsylvania immediately at planting and/or over-the-top.

Figure 1 - Comparison of the Xtend and Enlist weed control systems in Pennsylvania

To read the full article go to Pennsylvania Agronomic Crop News

Pennsylvania State Univ. Extension

TEC Talk Tuesday notes

Tuesday February 10 the talks hosted by Peter Johnson Real Agriculture mostly were about nitrogen and sulphur. Too many speakers to list all their names. But here are the highlights;

1.     There has to be a reasonable probability of N loss. One place is N early in the season to corn if you are not closing the slot when applying N.

a.     No need for N protection on loam soils to prevent leaching.

b.    Heavy soils could lose N if they are wet for a period after N application.

c.     Sandy soils could lose N by leaching, so late application is a good strategy.

2.    N volatilization losses from wheat ground early in the season do not occur (exception might be a spring like 2012).

3.    Adding humic will really not capture any N. Humic will decompose really quickly and will release N, not immobilize it.

4.    No research to show a response to N on soybeans (even though growers who win the high yield competition all add N).

5.    There is no N credit to a crop following soybeans.

After the session I messaged Dr John Lauzon with University of Guelph, to comment on adding a stabilizer to side dress N

Putting 28% on the soil surface at this time would indicate a high probability (due to the warm dry conditions at this time of year) of ammonia volatilization from the urea and the ammonium in the 28% indicating potential for urease inhibitor use. The actual benefit would be controlled by a number of factors.

  1. If it were applied just before a rain, losses would be minimal (need at least ¼ to ½ ” depending on soil conditions)
  2. Ammonia volatilization under the canopy of the corn would be much less than in an open field. Ammonia leaves the soil surface due to diffusion. Without any wind to carry the ammonia away, the concentration difference of ammonia in the soil compared to the air above would be small, resulting in less diffusion potential. How much reduction in loss that this would result in however I do not know. (Ed. I suspect plant height reducing wind makes a difference as well, along with the amount of surface residue).
  3. Although distributing the 28% over the soil surface may seem to increase surface area exposed to the air, it also increases the amount of soil in contact with the 28%. With a greater quantity of soil in contact there would be more pH buffer capacity keeping the pH from jumping as high as it typically would at the point of urea hydrolysis. Without the pH increase, the ammonical N would stay as ammonium, and there should be reduced loss. How much reduction I do not know, but it would be impacted by a number of factors like soil pH and buffer capacity. (Ed. While residue does increase the surface area the nitrogen hits, high residue environments are also favorable for higher populations of Urease, due to the high amounts of residue.)

At side-dress time I see minimal usefulness of a nitrification inhibitor, as the soil at that time of year is not likely to be wet enough for significant denitrification or leaching.


1.     You cannot build up sulphate in the soil. Need annual additions same as nitrogen

2.    Elemental S has to be oxidized to sulphate to be used by the plants

3.    No response to S with soybeans. (comments by several researchers)

4.    No research to show a response to S on corn

5.    Forages have the best response to S

6.    There is no accredited S soil analysis (Ed. Work is currently being done on this by one of John’s Master Students).

Three-year-old stands yield 15% less, four-year-old stands yield 30% less (notes from Dr Dan Undersander University of Wisconsin)

Great strides have been made in improving alfalfa stand persistence but yield still tends to decline after the second production year. Due to damage from wheel traffic, winterkill, and diseases in older stands. The chart below shows that over time, on average, yields in the University alfalfa variety trials have been highest in the first and second production years and then began to decline. (Editor’s note this is in research trials where there is no heavy equipment.) This yield decline has averaged 15% in the third production year and almost 30% in the fourth production year. All economic analysis would clearly indicate that it is more profitable to plan on shorter rotations and replant alfalfa fields more frequently, than to attempt to keep a low yielding field for another year or two. In addition, the cost of production goes up on the older fields with thinner stands, due to either lower quality forage i produced, due to inclusion of harvested weeds or expense goes up due to the need for additional fertilizer and less yield per harvest pass (harvest costs generally don’t change much regardless of yield)

Figure 2 - Effect of Stand Age on Alfalfa Yield (U of WI)

Command Herbicide

Command is a group 13 herbicide. It is registered on soybeans and numerous horticulture crops. It can be applied preplant or pre-emerge but not post. If it is worked in, you will lose efficacy. It gives good control of velvet leaf, annual nightshade, and lamb’s quarters. Even those that are triazine or group 2 resistant. It also controls green and yellow foxtail, barnyard grass, and crab grass. It can be tank mixed with products like Dual, Sencor Pursuit and another to broaden its weed spectrum. When it first came out there were issues with it volatilizing from the soil and causing damage to nearby plants in garden centers and even people’s homes. The current formulation is encapsulated to prevent this off-site movement. The label carries restrictions as to when it can be sprayed, similar to the various dicamba labels. There are also definite setbacks from sensitive plants.

Issues with Command herbicide. Command can volatilize after application and move to sensitive crops. I have had firsthand experience with this. As a result, I am reluctant to recommend this product, unless to a grower who knows how to handle it. It is used extensively on pumpkins and other vine crops. These growers know how to use it. Other issue is the restriction of not being able to plant wheat the year you apply Command. I have seen the activity and it is not worth taking a chance of spraying Command on any fields intended for winter wheat or a fall cereal cover crop.

Another option to control ragweed and lambs’ quarters in IP soybeans

Had a discussion with Mike Cowbrough OMAFRA weed specialist about IP weed control and how ragweed and lamb’s quarters are an issue on many farms. Mike said in his work he has been using about 0.33 L/ac of 2-4,D Ester 700 right after planting. This seems to give more control of ragweed and lamb’s quarters. Mike feels that since these two weeds germinate from a very shallow depth. The 2,4-D will control these seeds as they germinate. (I would not depend on 2-4-D alone on controlling these weeds, as the residual activity is fairly limited.) Note - the only product registered with a use pattern of 2,4-D ESTER post planting soybeans is Blackhawk.

How can I compare IP or NON-GMO yields to those of RR or Xtend genetics in the Ontario Soybean Trials?

It’s not easy but it can be done with abit of homework. In this case the grower has been growing OAC Wallace and is interested in knowing what the yield gap is between it and SeCan’s Altitiude soybeans. To make a comparison, I took the Ontario Soybean trials for the last three years for each variety. I then took the plot average for each trial and multiplied it by the plot index (as a percentage). This gave me the absolute yield. I included S03-W4s as well, as the same client was also wondering if they should try growing those, (usually have a higher premium than OAC Wallace).

Figure 3 - MG 0 RR vs. NON-GMO Soybean Variety Yields from GOSOY.ca

In another scenario a reader asked about comparing two different soybeans he was looking at growing.

Figure 4 - MG 1 RR vs. NON-GMO Soybean Variety Yields from GOSOY.ca

But you also need to know what your expected yield level is under your management and if there is too big of a spread at that yield level to switch between one herbicide system to another. I posted 3 charts below. Pay attention to the orange square. This is the intersection of $14 soybeans and a $2 premium (typical for non-gmo soybeans like OAC Wallace). Depending on your typical yield environment, it will dictate if you are giving up any gross revenues by growing one market class vs. another. If you’re farm average is 50 bu typically, the Altitudes will have to yield better than 7.1 bu/ac to offset the premiums, and based on the Ontario trials, that’s likely the case. (note I did not account for differences in seed cost and herbicides, those usually end up being about the same.)

Figure 5 - Acceptable Yield Lag by Soybean Price and Premium at 40 bushels/ac
Figure 6 - Acceptable Yield Lag by Soybean Price and Premium at 50 bushels/ac
Figure 7 - Acceptable Yield Lag by Soybean Price and Premium at 60 bushels/ac

% P Saturation – what is it and how to use it

I had a conversation last week with another crop consultant about Phosphorus Saturation on a soil test and how to use it. It’s the measurement of the ability of phosphorus to over come being tied up by iron and aluminum, then expressed as a ratio. P Saturation % is more heavily used on soils where dissolved reactive phosphorus losses are a risk of leaving the field and contaminating water supplies (think shallow water tables i.e. Florida). If you are at more than 25% P saturation, you are at risk of losing water soluble P. How would you use this information? It allows you to determine if you have two soils with the same soil test P in ppm and figure out if one soil posses a greater environmental phosphorus risk than the other. Perhaps you have a phosphorus responsive soil with a high P-saturation, maybe that field is better off having MAP applied at the time of planting, than a fall application.

Figure - 8 - Change Point in Water Soluble Phosphorus (Source V. Nair - U of FL)

If you are having trouble sleeping some night, you can find more information at the webinar link below.

Degree of P Saturation & the P Saturation Ratio: Theory and Calculations

An Ontario based agriculture podcast that’s easy to listen to…

Occasionally I get asked for what other types of content have been good in audio format. When I was driving to various meetings and clients, I looked for this in podcast format. One of the ones I found to be well done with relatively local content for Ontario and Eastern Canada cropping systems is Michelle Baker’s Prosperity Ag Out Loud. With this podcast, once a month Michelle has been interviewing Ontario based ag industry, farmers and researchers on topics ranging from mentorship, trying innovative practices, precision ag and more. You can find the podcast link below and on the Apple Podcast store.

Prosperity Ag Out Loud

Prosperity Ag Out Loud

Prosperity Ag Out Loud is for anyone who loves agriculture and the people within the industry. Host Michelle Baker interviews influential and inspirational people involved in all facets of crop production. This show dives deep into topics within each guest’s area of expertise and uncovers what ha...

Here are some closing comments from the one that featured Huron County based crop consultant Merv Erb…

1. Only plant the good stuff

2. P&K needed, more N doesn’t work

3. Watch the whiz bang; if you buy the tech, use it.

(Merv’s comment is, he sees lots of new things sitting in fence rows…)

“Hoping for the best, prepared for the worst, and unsurprised by anything in between.”

—Maya Angelou