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The Cropwalker - Volume 3 Issue 20

Always read and follow label directions.

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Crop Conditions

Winter wheat- earliest has head in boot. (One field in Essex has heads emerging) Timing for T-2 fungicide application is at flag leaf. There are a lot of fields that will all of a sudden be showing a head. This hot weather will make the wheat go through the next stages quickly. This is the type of weather that means you do not need a growth regulator. The hot weather is making the straw short. But straw yield will be good. With flag leaf fully extended it will be 2-3 weeks to Fusarium Head Blight (FHB) timing. Typically, you can expect 2-3 weeks of leaf disease protection with a fungicide. The strobi group of fungicides prevent spores from germinating. They do a great job giving protection from stripe rust which is now more prevalent in the US. You cannot spray a strobi once the head appears. That is when you switch to a triazole (Caramba, Miravis Ace, or Prosaro). Corn - Check populations. There are some areas with poor emergence and some replanting. The earlier worries about frozen corn seem to have gone away. There is uneven emergence. Nothing you can do about that now. There is a lot of talk about uneven emergence. But if one area of the field emerges later than another area that is not as bad or as important as plants that emerge unevenly when they are side by side. If you have uneven emerging plants dig down and see if you can find the reason. Most common reasons are, seed to seed difference in planting depth. Seed firmers or rebounders are supposed to remove some of this uneven seed placement. Rough seed bed conditions, stones, too fast planting speed are the main reasons for uneven seed depth. To me uneven plant emergence is not really critical if you have populations of 30,000. If your population is 26,000 uneven emergence is more yield limiting. Soybeans planting resumed. Earliest planted fields are popping through. Some replanting in areas where crust prevented emergence. In this weather soybeans can be up in 2-3 days after planting, do not wait to get your pre-emerge on.  Forages At least one farm has made first cut because of feed shortage. Hot weather will bring more acres ready to cut real soon. A lot of fields were held back because of the cold spell. Don’t give up on alfalfa. In these fields first cut will be 4-5 days later than normal. Get your first cut and if you still think the field is poor, you can plant corn silage June 10. (Lot of June 10 planted corn last year yielded great) New seeding is at unifoliate to first trifoliate. Reminder that there is less crop injury to seedling Alfalfa spraying Embutox at the start of the labelled 1-4 trifoliate stage, than later. Spring grain is from 3rd leaf to first node visible. Now is the time to apply weed control. If applying a fungicide, recommend using a product that contains both a triazole and a strobi, vs those that just contain a strobi (Tilt/Bumper/Pivot). This could mean the difference between 1 week or 4 weeks of suppression on leaf diseases (varies by disease and product).


Question How come the alfalfa is suddenly ready to cut?

Alfalfa was producing new cells at a normal growth rate during the cool weather. Now when we get heat suddenly all those cells expand, and alfalfa is ready to cut.

Corn Yield at Various Populations

Corn is emerging variably in some fields. The table gives some indication of expected corn yield with various populations. I put this table together extrapolating from older research and higher populations. This table refers to expected yield if corn is planted before May 10. Different numbers apply to earlier and later plantings. If you have 20,000 good plants suggest leave it. It is next to impossible to “thicken” a corn stand. If you are checking areas put a drainage flag or even a pile of stones in the 1/1000 of an acre you are checking. (30” rows 17’ 5” in 1/1000 acre. 20” rows 26’2” 1/1000 acre)

Figure 1 - Estimated Population and Yield Potential

Corn Yield Loss Due to Uneven Emergence

There are some misconceptions. If corn emerges at different times in different areas of a field, like the sandy area emerging sooner than the heavy area, this is not a yield reducer. It is when individual plants in a row, side by side, emerging at different times is a yield loss. Research shows that individual plants that emerge 10 days late will have an 8% yield loss. Individual plants that emerge 21 days later have a 10-20% yield loss. If you have plants that are 2 leaves different, there will be a minimal yield loss. Plants that are 4 leaves behind fall into the 10-20% loss. If 20% of corn plants are 4 leaves behind the rest this could be 5-10% overall yield loss. If 20% of the plants are 3 weeks delayed emerging you should find out why. Isaac Ferrie has a good thread on this when evaluating replant decisions and taking both population and stand variability in to account.

Yields with Reduced Soybean Populations

It is amazing how well low population stands can yield. This research was done by hand-thinning a good stand. Survivor plants were healthy. In real (your) fields, stands are reduced and remaining plants are not always healthy. Consider these yields as best case. (Consider reducing your yield expectation by 20% with the populations in the table). Check your population from previous years and compare to final yield. You may be amazed as to how good a yield you had another year with a low population. Inter-planting corn into an existing corn field seldom works. Inter-planting soybeans into a stand works. If replanting, consider staying with the original variety. Consider dropping 120,000 seeds. Experience suggests that when you replant in 7” rows you lose 50% of emerged plants. If you are in 15” rows you lose less. You may have to drive the whole field to touch up certain areas.

Figure 2 - Estimated Population and Yield Potential By Row Spacing

Question – How many plants do I need in an alfalfa stand the year of seeding?

Answer. You plant about 16 pounds of alfalfa seed per acre. This equates to about 75 seeds / sq ft. So, in 7” rows this is about 45 seeds / foot of row. A lot. So, if you have 20 per foot of row at establishment that is lots. The chart below gives an approximate number of plants through the life of a forage stand. The ideal is we want 50 stems or more per square foot. These are all book values. In reality when you look at a new seeding it is either good or not good. Generally, no one actually does a plant stand count. If you are assessing your stand and are not satisfied check seeding depth. Number one reason for poor stand establishment is planting too deep. If you have a poor stand, then reseed poor areas right now, as you will not be able to reseed once it’s established.

Figure 3 - Alfalfa Plants per Square Foot

Question Is there more denitrification in a band vs broadcast incorporated.

There are several types of nitrogen loss. Two or three of biggest concern to farmers are Volatilization (gassing from Urea), Denitrification, and Leaching. Denitrification is the process where N changes from the plant available nitrate form to a nitrous oxide that can escape as a gas. This occurs in oxygen limited soils (soils that are fully saturated, beyond field capacity). You will have parts of the field at greater risk of denitrification, these will be areas that collect water. The soil microbes use oxygen from nitrate in these situations to continue to survive. If the soil is oxygen limited, it will not matter the way nitrogen was placed into the soil, you will have losses. We want N to change into the nitrate form to be taken up by the plant. But once in the nitrate form it can be leached or further changed into a form that can escape into the air. There is a lot of research on nitrogen. Reading many research reports indicates some things. Of the nitrogen (N) you apply only about 50% is utilized by the crop. There is a big range of 25-75% used. The rest of the N comes from the soil.

Recent research on shallow-banded nitrogen application indicates the practice may not be as agronomically sound as once thought. Concentrated shallow bands (less than two inches deep before packing), of urea or UAN, may have higher volatilization loss than broadcast or surface-band applications, while shallow tillage of less than three inches may be insufficient to protect urea from volatilization losses. Some research reports state with good evidence that incorporating N will reduce volatilization but may not increase yield. See article below on additional information on N stabilizers.

Figure 4 - Nitrogen Cycle

Nitrogen Stabilizers and Rates -  The next best option to splitting your Nitrogen applications in corn is to add a N Stabilizer with your PRE applied urea or UAN. 1. Agrotain Ultra is a liquid product that can be added to UREA or UAN – it contains a urease inhibitor and offers “above-ground” protection of N loss by volatilization. Its application rate is 3.1 L/mT of urea, and 1.55 L/mT of UAN. Agrotain Advanced is a more concentrated version of Agrotain Ultra and performs better on Urea. 2. Agrotain Plus SC is a liquid product that can be added to UAN. It contains a urease inhibitor and a nitrification inhibitor, so offers “above” and “below” ground protection of N loss from volatilization AND denitrification.   Its application rate is 11 L/MT. 3. Entrench is a nitrogen stabilizer that contains nitrapyrin, a nitrification inhibitor. It offers “below ground” protection from loss. Its application rate is 1.1 L/ac. It has a per acre rate, while both Agrotain products have a per treated product rate.

Figure 5 - Common Nitrogen Inhibitors

Question I have shepherd’s purse and maybe stink weed in my established alfalfa. Can I spray to control these weeds?

Answer NO. Basagran is pretty good at controlling shepherd’s purse and stinkweed. But the forage must not be used as feed. This registration is for seed fields only. Also, by now these winter annuals have done their damage and will not grow much more. Controlling them will not help your forage yields.

Question I think the weeds in my forage field came from forage seed. How can I figure this out?

Answer This is one of the most common weeds in forage questions I get. The solution to figure this out is: 1) Are the weeds general through the field or mainly in certain areas. Generally, they are just in certain areas which means the seeds were in the field before you seeded forages. Even though you have not seen these broad-leaf weeds before the seeds can lay dormant for years. (Seed has been recovered from Herod the great’s Palace in Israel. The seeds were carbon dated to be 2,00 years old. Some weeds seeds can live a long time. 2) The other test is are the weeds all in the rows of forages or are they also between the rows. Typically, they are mainly between the rows.

Temperature swings when spraying corn

The guidelines are not to spray if above 28 C or if there is a 20 C swing in temperature during a 24-hour period. But if you don’t get the weeds controlled there will be a yield hit. Points 1) Smaller corn plants with less leave surface are damaged less. 2) If really hot better to spray in the evening. The corn plant will break down herbicides in the first 12 hours after application. In the evening corn plants can more easily break down herbicides.

Psst… you don’t need to scout the whole field.

I’m not suggesting cutting corners. If there is one thing I despise, it is poor quality workmanship. I’m suggesting you only need to check enough of the field to ensure you have covered all the areas that behave the same way. Call it directed scouting. These areas that “behave” the same way, are likely to have the same emergence issues, similar weed spectrum, similar nutrient deficiencies, similar tillering, you get the point. Now, if you need a map to start with, I know a guy.

How to do variable rate crop protection – a few ideas

1.     The label is the law. If there is not a rate range with the product in question, you are limited to an on/off script. If there is a rate range within the label, it must be applied to the parameters outlined in the label (i.e. soil texture type for Sencor, for example), or weed size for post-emerge products.

2.    Soil applied products (i.e. Boundary, Primextra, Sencor, Atrazine, Treflan/Rival), should have a soil-based map. Primary driver for efficacy on these products is a combination of soil texture/organic matter and/or soil pH. Improved herbicide efficacy and reduced crop injury are the expected benefits.

3.    For spraying a burndown, products like Roundup, for example, using an “in-season” image that sorts out biomass vs bare soil would be appropriate. Although I can’t say I’ve seen many examples of trying to apply glyphosate at different rates (0, 0.67, 1.33 L/ac within in the field.) The most commercial application I have seen on the market is WEEDIT, which sprays if there is anything green present. The expected benefit in this situation is to avoid applying post-emerge herbicides to bare soil.

4.    For spraying in-crop, which for most products, likely means an on/off script, the use of RGB or NDVI imagery can be quite useful. The goal is to avoid applying products to areas not appropriate for the application timing. BASF has commercialized Xarvio in Spring Canola for this purpose.

Spring Cereal Herbicide Update

FMC advised they have received registration for Barricade M on oats. So, you can now use it on Oats. The labels listed on the website should be updated in the near future.

Figure 6 - Updated Spring Cereal Herbicide Chart

Mystery Weed

Picture was taken yesterday, so these plants are up and at it.

Picture 1 - Mystery Weed for week of May 25