August 14, 2013

Agronomist Notes

Hello Reader

We’ve finally had a dry spell with little rain and some decent temperatures. The 14-day trend calls for temps in the mid to high 20’s with a chance of showers. We may just get the August we need to mature this crop before the first fall frost. Desiccation has just started on peas, canola swathing will begin next week with malt barley harvest just around the corner.

In this issue of Beyond Agronomy News, we’ll look at pre-harvest spraying in hot temperatures followed by a few tips on desiccating peas. Last, I’ll discuss desiccating pulse crops using GreenSeeker technology. We’ll finish with technical grain market news.

Photo: Late maturing canola shows compaction caused by slippage, near Three Hills, AB. S. Larocque

Crop Staging

(Calgary to Drumheller to Three Hills)

Seeded May 1-7 May 8-15 May 15-22
Wheat Medium dough Soft dough Milky dough
Canola Late podding Mid podding Early podding
Barley Hard dough Medium dough Soft dough
Peas Preharvest Late pod Mid podding

Steve's tips & tricks of the week

Follow me on Twitter for in-season updates @BeyondAgronomy

We're now on the tail end for sweeping for lygus bugs in canola. My thresholds are at 5/sweep at this point on later maturiing canola.
Scout for Bertha Armyworms in canola, some select fields are at threshold levels.
Book your Reglone or desiccant now while supplies last.
Purchase glyphosate for pre-harvest before preferred products are sold out.
Look for uneven patterns in fields to address seeding depth or residue issues and correct them before next year.

Pre-harvest spraying in hot temperatures

Each year we are typically faced with hot temperatures in August when we’re trying to apply pre-harvest glyphosate. The current rule of thumb when spraying in hot temperatures is to shut down around 26-28C. The main reason for shutting down under hot temperatures is because of the possible reduction in herbicide efficacy from evaporation. If herbicides like glyphosate evaporate too quickly they will turn into a solid and require rewetting to come back into solution. Plants can only absorb herbicide in solution. Secondary is the possibility of plants shutting down under high temps and no longer taking up herbicides.

The key to spraying in higher temperatures is to consider both temperature and humidity. High temperatures coupled with high humidity levels allow liquids to stay in solution longer and penetrate leaf surfaces compared to low humidity.

These are the guidelines I use when spraying in warm temperatures:
1) Spray at 26C if humidity levels are above 40%.
2) Spray at 28C if humidity levels are above 45%.
3) Spray at 30C if humidity levels are above 50%.
4) Spray at 32C if humidity levels are above 55%.

The information I use for spraying in high temperatures is based on the Delta T method developed in Australia. High humidity keeps droplets in solution longer even though air temperatures may be high. So, when you’re out there this August and the weather is hot, remember to check your humidity levels to see how long you can spray. Maybe you don’t need to be shutting down so soon and can actually get some spraying done. SL

Photo: S. Larocque

Quick tips on desiccating peas

Many people confuse desiccating with pre-harvesting. Desiccating is a tool used to rapidly kill vegetation, be it weeds or crops above ground. Products like Reglone or Heat could be considered desiccants, unlike glyphosate which is not a desiccant. Glyphosate is generally used for perennial weed control and controls vegetation from below the ground, slowly.

As we quickly move into desiccation season I thought I should provide a few tips on application and timing.

Tips on application

If you have a buckwheat problem in peas, use Reglone versus glyphosate. Glyphosate is useless on wild buckwheat.
If you have perennial weeds like Canada thistle, quackgrass, perennial sowthistle or dandelions, glyphosate would be a better option so long as you can wait for the crop to mature which might be 10 to 14 days.
Desiccation will not help immature seeds to mature. You can lock in green seed in yellow peas by desiccating too soon.
Water volume is key with Reglone. At least 15 gal/ac should be used and even better with 20 gal/ac. It is a contact herbicide and kills only what it touches.
Don’t forget to add a non-ionic surfactant with Reglone. If you have waxy leaf surfaces on weeds or the crop from drier weather, double the recommended surfactant rate.
Use the 800 ml/ac Reglone rate with heavier pea crops or weed infestations or slow down in the heavy, green areas to apply more solution.
Apply in the evening for best results. See photo above.

Application timing

Upper pods

Pods are fleshy green or starting to turn yellow
Seeds may be immature but still split when squeezed.

Middle pods

Pods are light green to yellow
Seeds are full-size and soft, but not juicy
Seeds will split when squeezed

Bottom pods

Pods are dry and translucent
Seeds are detached from pods

You should be able to combine within 5 to 7 days after application. SL

Pictured above: The difference in dry down time between spraying Reglone in the daytime versus nighttime is significant, according to research by Syngenta.

Photo source: Syngenta

Desiccating pulses with GreenSeeker

This fall we plan to desiccate our faba beans with Reglone (diquat) to speed up dry down. With $18.00/ac Reglone you certainly don’t want to waste it or apply it in areas where the crop is already dried down. We have a unique opportunity to vary the rate of Reglone using our GreenSeeker. Looking at the variability in maturity on many pea fields, a Trimble GreenSeeker or AgLeader OptiRx could make better use of desiccants by adjusting the rates according to the crop maturity or weed pressure.

The cost for a 6 sensor GreenSeeker is roughly $14,000 plus the cost of the FMX monitor which brings the total cost to just over $20,000. You can save a few thousand by purchasing a Nomad handheld or a Yuma tablet also. An AgLeader OptiRx would cost roughly the same. The trick with the GreenSeeker is to buy a handheld GreenSeeker ($500.00) so you can measure NDVI values and set up product rates in the FarmWorks mobile software before you enter the field. You can walk into thick, green areas and fully mature areas with the handheld and measure the NDVI values. This allows you to match NDVI values with what you see in the field to get a better handle on how much you should increase or decrease rates across the field.

To give you an example, NDVI values range from 0 to 1 with 0 being bare soil to 1 being a thick, green canopy. In our case, NDVI values from 0.1 to 0.4 may get no product at all, 0.5 to 0.7 may get a regular rate of 600 ml/ac and high NDVI values from 0.8 to 1 will get an 800 ml/ac rate to really help those thick, green areas dry down quickly.

A GreenSeeker is a tool that allows you to address in-season variability like we normally find when desiccating pulse crops. At $18.00/ac, you can generate a fairly quick return on investment if you grow more than 500 acres of pulses each year. The end result is a more effective, faster dry down that standard flat rates can’t provide. We look forward to testing the theory this fall on our faba beans. SL

Link to GreenSeeker

Local Trimble rep:

Link to OptiRx

Local AgLeader rep:

Photo: Field peas maturing unevenly. Image captured in a drive by photo shoot. S. Larocque