# How long between split prodiamine apps?



## sean_h (Jan 31, 2020)

Planning on doing split prodiamine apps (granular HJ 15-0-7 .37% prodiamine) once soul warms up.

First app will probably be late-March (15 April Tax Day at the latest). But how long should I wait between applications? 6 weeks? 12 weeks?


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## Vtx531 (Jul 1, 2019)

The total applied amount (1st+2nd apps) determines how long the effect lasts. The time in between is just insurance in case it gets washed out or some other complication. I did four weeks between applications of pre emergent last year with good results. April 15 and May 15 in SW Michigan. Make sure that you don't apply so much that your coverage window goes into fall if you intend on overseeding in fall.


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## Green (Dec 24, 2017)

Let's say you're splitting a 4-month rate in half. You generally want to put down the first half early enough that it's before crabgrass or other target weed germination, and the second half while the first is still active, but not so early that your coverage is expected to end before the desired date (about 2 months plus whatever is left from the previous app).

In practice, this might mean a first app before 55 degree soil temps are reached, and a second app about 4-6 weeks later, once soil temps hit 65 or so. I like 6 weeks because it's about 2/3 in between the span of the coverage duration.


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## jeffjunstrom (Aug 12, 2019)

What are the advantages/disadvantages to one app/split apps? Similarly, why not use the max app rate to ensure full season coverage? I understand if you have a fall renovation/reseed planned, that's different. But for the average spring/summer/fall coverage, why not maximize the coverage and apply once in early spring?


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## Green (Dec 24, 2017)

@jeffjunstrom, that's 2 different questions. As you say, not everyone needs or wants a barrier all year.

As far as why to split it up in Spring, it's often personal preference and wanting insurance in the middle of the Summer season when weed pressure is highest. The app will be fresh at that time. You never know if environmental conditions might have degraded the chemical, either, so topping it off helps.

I'm more of an apply once in early Spring and then let it run out person. It's just easier.

Hope that helps.


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## corneliani (Apr 2, 2019)

For y'all in the north it almost doesn't make sense to split the apps, since your season is relatively short (April to Sept?). But for the southern/transition folk whose first round goes down as early as Feb, sending in reinforcements come April is a lifesaver. Not only can we mitigate for the unexpected spring weather but we can extend our coverage into & through the hot & long summer months.


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## g-man (Jun 15, 2017)

@corneliani it makes sense to split in the north too. Purdue did a study round this. See table 2.

The prem does have a decay (likely exponential), so the protection is not constant. The UV /heat further accelerate this decay.

https://turf.purdue.edu/wp-content/uploads/2012/06/15_AGRY_Patton_sequential20apps.pdf


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## jeffjunstrom (Aug 12, 2019)

This will be my first year applying a pre-m so I appreciate the insight. I think I probably would have been a "set it and forget it" guy, it doesn't surprise me that the study shows split app is better. Thanks, y'all.


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## corneliani (Apr 2, 2019)

g-man said:


> @corneliani it makes sense to split in the north too. Purdue did a study round this. See table 2.
> 
> The prem does have a decay (likely exponential), so the protection is not constant. The UV /heat further accelerate this decay.
> 
> https://turf.purdue.edu/wp-content/uploads/2012/06/15_AGRY_Patton_sequential20apps.pdf


What was the "label rate" they used, 0.75# a.i./A??


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## g-man (Jun 15, 2017)

In the research world the use real measurements. 0.75lb of the active ingredient / acre rate.

The product we normally use is 65% active ingredient. So converting to the product we use, 1.15lb/a. Converting to ksqft, 0.0265lb/ksqft. Now converting to oz, 0.42oz/ksqft. (In grams it is almost 12g/ksqft.)

By the way I like to use grams for this since it is more precise on my scale. I typically do 5g/ksqft applications, 3 times a year if I'm not renovating.


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## sean_h (Jan 31, 2020)

I have about 5 lbs of the same stuff leftover from last year, so that makes 55 lbs total, divided by two applications of 27.5 lbs per application... and with a 9,000 sq ft lawn, that'll get me about 3 lbs of product / 1,000 sq ft. (just over the minimum amount). And with 15-0-7, I'll get about .4 lbs N on the ground per application.

Gotta love a little #FertMath


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## Green (Dec 24, 2017)

Yeah...as alluded to, splitting a 4-month rate is by no means necessary, but if you have high weed pressure it can be helpful. I would say it makes "more sense" to do a split for those who are more South, especially if using something like Dimension. Your period is more than 4 months...more like 6-7.

Certainly with Pendimethalin, the split app is pretty much required no matter where you are due to the lower concentrations normally used per app (which yield a shorter residual). Those in the South may have to apply it more than twice to get from Spring to late Summer. (I will be using some Pendi this year, so I researched it all ahead of time.)


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## TN Hawkeye (May 7, 2018)

sean_h said:


> I have about 5 lbs of the same stuff leftover from last year, so that makes 55 lbs total, divided by two applications of 27.5 lbs per application... and with a 9,000 sq ft lawn, that'll get me about 3 lbs of product / 1,000 sq ft. (just over the minimum amount). And with 15-0-7, I'll get about .4 lbs N on the ground per application.
> 
> Gotta love a little #FertMath


What is the protection window for the minimum?


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## sean_h (Jan 31, 2020)

TN Hawkeye said:


> sean_h said:
> 
> 
> > I have about 5 lbs of the same stuff leftover from last year, so that makes 55 lbs total, divided by two applications of 27.5 lbs per application... and with a 9,000 sq ft lawn, that'll get me about 3 lbs of product / 1,000 sq ft. (just over the minimum amount). And with 15-0-7, I'll get about .4 lbs N on the ground per application.
> ...


Four months.


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