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The Cropwalker - Volume 3 Issue 18

Always read and follow label directions.

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Crop Conditions

Winter wheat latest is at almost first node earliest is second to third node. At first node the developing head is above ground. If we get -4 o C at this stage it can damage the head. If the developing kernels are frozen, they will not develop. There may be some areas in some fields where heads did freeze. Not sure as to how this will affect yield as generally the tillers will add more to final yield if the main head is damaged. Nothing you can do but wait and see. Once the head emerges you should be able to determine if it is damaged. Luckily, areas where wheat that was at first node did not get the -4 o C. Stripe rust was detected on wheat in the US mid-west on May 5th. According to folks there they say “conditions are favorable for disease development and spread. This is a cool season disease that loves wet weather and temperatures between 8 and 18 o C. Fields should be scouted for the disease, keeping in mind that it often starts in small pockets, or epicenters in a field, and may not be widespread.” Spraying a T1 fungicide (check label) will control stripe rust. In my travels, some winter wheat fields are starting to look like they are going backwards. The wheat is cold and hungry, but also any growth is showing bare spots due to flooding or heaving. If you have split applied the nitrogen on the wheat, and need to do a second pass, strong consider upping the planned nitrogen and sulphur rates. With the current weather conditions, very little is mineralizing.  Corn planting is probably 70% complete. Some growers are finished. The Haldimand and Niagara clay areas have not started. Soybeans planting stopped over the weekend due to cold soil conditions. Probably 15% planted. Forages we will probably see some damaged leaves in fields where the night temperatures were low. Forages will survive. This is the week to spray Priaxor. (see below) Spring grain is emerging well. Once weather warms it will be ready for weed control. Generally, growers wait too long to control weeds in spring grains. Spring grain yield is held back by weeds like corn and soybeans. Critical weed free period is 3-5 leaf. Insects there is a significant catch of Black Cut Worm (BCW) moths in the US mid-west. This really does not mean there will be a lot of BCW since a lot can happen between when moths start to fly and BCW larva start to feed. They like cover crops. Weed control you need warm weather +5 C in the 12-24 hours before and after spraying. Best control will occur when sun is shining. Increasing the rate (higher label rate) of post emergent herbicides may improve control.

Figure 1 - Estimated Corn Progress
Figure 2 - Estimated Soybeans Progress


Imbibitional Chilling Injury of Corn (University of Nebraska Newsletter letter)

When corn seeds imbibe (take up) water, cell membranes stretch, and cells expand. When a damaged cell membrane rehydrates, it may not return to its normal shape and size. This can create a "leaky" cell. Water is at its densest at about 4°C so when cold water is imbibed, it may result in additional membrane damage. These ruptured membranes may occur in the cell walls and in the mitochondria. In the plant this action may disrupt the embryo/endosperm enzymatic conversion to energy, but mostly results in leakage of cell solutes and sugars. This, in turn, is likely to reduce growth rate and interfere with growth of the emerging seedling. Debate exists about what specific temperature and timing causes imbibitional chilling. However, corn plants that imbibe cold water (in the low 40s) in the first 48 hours after planting undoubtedly are affected. Planting when soil temperatures are above 10°C alleviates concerns of imbibitional chilling affecting corn emergence. Some scientists suggest that corn will not be injured at soil temperatures as low as 4°C; however, there is certainly some risk of injury from imbibitional chilling at those low temperatures. Some inbred lines (seed parents) are clearly more susceptible than others, and the seed industry has been actively eliminating the most sensitive ones from use. However, if environmental conditions are extreme, many tolerant parents may still show damage—imbibitional chilling is a physical phenomenon that can override biology and genetics. (So basically, they are saying there could be some damage.)

I asked classmate and corn breeder for 45+ years Francis Glen of Glen Seeds about imbibing in cold soils. He said

I am glad to have arrived at this advanced age with many seasons of experiences and not have experienced this before. Our fruit grower neighbors took a devastating hit last night. I looked at corn I planted 7 days ago???

Ears of corn sit on and in soil all winter and the seeds germinate. Imbibing water is a temperature driven process so I expect that corn recently planted has not gotten warm enough to have taken in water that would cause ice crystal damage to the cells. Seed in storage freezes with good germination because it is dry. The seed that was planted this past week could be fine, if we get warm weather and a warm rain.”

Then I asked a corn breeder from one of the main corn companies in Ontario

Pat - yield depends on emergence rate but I would say 5-10% yield loss could be typical; could be less, could be more. Corteva has a lab test to screen this type of condition and leads to the stress emergence ratings in the product catalog. Genetics and seed source both contribute.

Photo by Dr Bob Neilson Purdue

To me this all says we do not know. Damaged plants will either not emerge or will emerge and be stunted. We will know by the 4-th leaf stage.

Figure 3 - Imbibitional Chilling in Corn

Spraying Priaxor on Alfalfa

This is the week. Research from BASF suggests you should expect a 10-20% increase in first cut yields, with increase in protein, because you are saving more leaves (better leaf retention lower on the stem). Priaxor should be applied 21 days before harvest. Research has shown that if you cut before 21 days you lose some of the benefits of spraying Priaxor. The harvest interval is 14 days between spraying and harvest. If you harvest later than 21 days, you still gain benefit from Priaxor. BASF also presented some data in the winter that they saw effects the following cut as well with faster regrowth. Something to consider for intensive alfalfa growers.

What Causes Manganese (Mn) Deficiency?

Mn is very reactive in the soil. It is taken up as the Mn++ ion. If there is air in the soil this Mn++ ion quickly changes to the unavailable manganese oxide form. (You sometimes see dark green in wheel tracks. This is because air has been pushed out of the soil and Mn is still in the ion form) This deficiency appears as light green areas in the field. Closer examination will show striping of the leaves with the interveinal areas being a bit lighter. The reduced growth of the plants will also appear as if nitrogen is deficient. Often Mn deficiency will appear between tile runs but over the tile run is a darker green. The deficiency is most obvious on lighter or muck soils which are naturally low in Mn. Other soils prone to Mn deficiency are soils with a pH over 7 to 7.5. As the soil warms it releases Mn from organic matter. With cold soils very little is released. Cold soil also means roots are feeding shallowly where there is less available Mn. Some years the soils warm up fast and release Mn from organic matter. If the soils are warm and airy available Mn converts to the unavailable Mn form. Colder, wetter clay loam soils with a pH above 7.5 will be more prone to Mn deficiency. We are also taking more Mn from the soil with higher yields. From my experience if you have visible Mn deficiency you need to spray twice.

Antagonism Between Metribuzin and Glyphosate

Clay based products like metribuzin (Sencor/Tricor/Boundary/Conquest, etc.) can tie up glyphosate. The table below indicates that 1.0 L/ acre of a 356 gm/L glyphosate loses some activity on perennial weeds, such as, dandelion, and perennial sow thistle. Annual weeds like mustard, and lamb’s quarters, are not affected. This antagonism is overcome by increasing the rate of glyphosate. In this research 0.25 L/ac of glyphosate (356 gm/L) were needed to overcome antagonism for perennial weed control.

Figure 4- Glyphosate rates and Weed Control when tank mixing Metribuzin (Sencor/Tricor)

WALES Tank Mixing Order for Products

Figure 5 - WALES Tank Mix Order

Herbicide Mixing Order WAMLEGS (includes microencapsulated products like Prowl)

Figure 6 - WAMLEGS Tank Mix Order

Growing Degree Days – How to calculate

Cereal crops use a base unit of 0 C. That means you use the average temperature reached that day, and that is the number of degree days accumulated (10-0=10) Corn and soybeans use a base unit of 10 C. This means you would take the day’s average temperature and subtract 10, giving you the number of degrees you have accumulated for that crop. (10-10=0). This is why cool weather crops continue to advance, while warm season crops more or less stop growing. When crops have yet to emerge, you should be using soil temperature to forecast crop emergence or development. I’ve put together an example below, brown is below ground tempearture, blue is air temperature.

Figure 7 - Growing Degree Days of Various Crops

Soybean Planting and Temperature

Based upon my reading on planting soybeans into cool soils, research in Manitoba and Ontario suggests that once the risk of frost has passed (when soybeans would emerge), planting date plays a bigger role in final soybean yield than soil temperature at planting, especially if soils are fit (which most are today). The number one deciding factor on whether you will have success in cold soils, or not,  is seed quality. Soybeans emerge within 24-35 days when seeded into 6-12 C soils, and 4-16 days when seeded into 14-22 C soils (based upon soil temperatures at 2”, for two consecutive days) (Manitoba Pulse and Soybean Association data).

Spreader Misapplication

If your using a spreader, and it was not calibrated for the product being spread, expect to have an uneven spread pattern. Prior to GPS we use to blame spreader performance on the guy’s driving habits. Once everyone could drive straight every 40, 50 or 60’, then it was fairly obvious the machine just wasn’t quite dialed in. When they are calibrated for the product being spread, it is quite impressive how accurate the spreader can be.

Why should I top-up the Metribuzin in Boundary when spraying Pre-Emerge?

You should consider topping up the metribuzin portion in your Boundary IF a) you do not have triazine resistance and/or b) you farm fine textured soils. By doing this you should expected improved control on non-triazine resistant weeds, such as lamb’s quarters, mustard, and common ragweed control. Also, may improve control of Lady’s Thumb, Wild Buckwheat, Cocklebur, and glyphosate resistant fleabane.   On Medium Textured Soils, using 1 L/ac of Boundary provides enough metribuzin in most instances. Higher rates may increase crop injury without additional benefit on weed control. On Fine Textured Soils, consider using 1 L/ac of Boundary plus topping up with additional Sencor.

Figure 8 - Soil Type by Metribuzin Rate

Winter Wheat – Cold Tolerance by Stage

I am freezing!!!!! Were my thoughts last week trying to do outside work. Here in the expected cold tolerance for winter wheat at various crop stages. Jointing = stem elongation (where we are now).

Figure 9 - Risk of Freeze Damage in Winter Wheat

Source of Table for Winter Wheat Freeze Damage

Spring Freeze Injury to Kansas Wheat

Engarde vs Primextra

A client recent asked if he should be using Engarde or Primextra pre-plant/pre-emerge. We ended up deciding on using Engarde based upon a few factors. 1) Fleabane is starting to show up in his area. 2) He is in an area with significant group 5 resistance. 3) Aside from perennials, there is a good chance he will not have to go back in and spray in-crop. Pick the product that fits the weed spectrum, the cheapest weed control is the one that controls the weeds on your fields.

Mystery Weed – Another Winter Annual

Figure 10 - Mystery Weed of the Week

Mystery Weed - Purple Deadnettle

Ran out of space in last week’s newsletter, but the mystery weed from 2 weeks ago was Purple Deadnettle. The easiest way to determine its purple deadnettle and not henbit, is the check the stem. Square stem means its Purple Deadnettle. One reason this weed is significant from an agronomic standpoint is that it can be a host for Soybean Cyst Nematode. It is also incredibly prolific, causing yield losses of up to 38% in winter wheat, to avoid this yield loss, you would have to have controlled it in the fall. Because it is a winter annual, it typically is not an issue in corn or soybeans, usually taken out by tillage or a spring burndown. Products such as Infinity/Infinity FX or Refine M/Barricade M are options for spring control.

Figure 11 - Purple Deadnettle

Nurtrient Availability in Cold, Dry Soils

The primary nutrients to be impacted under the current weather conditions are ones that rely on a biological process to provide availability to the crop. Examples of these include; Nitrogen, Phosphorus, Sulphur, Manganese and Boron. With the current weather conditions, expect larger than normal response with applications of these nutrients (provided place, rate, product and timing are appropriate).

Crop Protection Application Timing Terminology

Figure 12 - Crop Protection Application Terminology

Crop Modelling – Winter Wheat and Rainfall

I’ve been working on try to find a few crop models to benchmark my area’s yield potential vs. what has actually occurred. One model used in winter wheat is French and Schultz. This model is very basic and uses the growing season rainfall in millimeters less evaporation multipled by a set yield rate per acre. I couldn’t find data to support an evporation rate for Guelph, so I left that blank. I did put in a few assumptions on 30-year data for off-field moemvent of water through run-off or infiltration. Bottom line, rainfall is typically not a limiting factor for Ontario wheat yields. The author’s of this newsletter both feel that if you would like to increase your wheat yields, the number one factor is to move up your planting date to have a bigger root system going into the grainfill period. The number two factor is to increase your wheat density, to increase the number of heads from main stems. Winter wheat after oats, anyone?

Figure 13 - French and Schultz Wheat Yield Model

All models are wrong, but some are useful.

-George E. P. Box – British Statistician