Chemical mixing, please read and give your 2 cents

Jason Rose

LawnSite Fanatic
Ok, I have been spraying for four years or so but not at all full time. I spray probably 2,000 gallons of mix per season (20, 100 gal. tanks). Here's what I still don't get... How can a mix of 3-way herbicide for example, let's say 1.5 ounces per 1,000 sq. ft. How can the rate be the same like the label says if you mix that 1.5 ounces of chemical in 1,2,3,4,or 5 gallons of water!!?? I can understand the this being correct for a preemergant or non-contact insecticide but how does a 'contact' type chemical work the same if it is DILLUTED in 1 or 5 gallons of water assuming that 1 to 5 gallons is spread over the same amount of area.

Basically I am getting very poor results when I mix, say, 1.5 ounces per 1,000 of 3-way at a 3 gallon per 1,000 rate. BUT if i am to mix it at 1.5 ounces per GALLON like I want to I am triple over my spray rate per k. I have notr found a way to get my lesco/chemlawn gun to spray that low of a volume, nor would I even want to. I like to get the weeds/grass consistantly wet with spray and 2-3 gal per k seems to do that well but at the dilluted rate I have to spray then I am still getting poor to very poor results.

Many times I do spray in the mornings, usually when there is dew on the lawns, I know this must be also dilluting my spray even more. I just can't win! How do the big guys do it and get good consistant results? It is so hard in Kansas to catch a day that the wind isn't blowing, you have to spray when you can.

If this isn't at all clear feel free to ask me questions, Thanks guys!


LawnSite Member
I know myself I've used premixed before with poor results sprayed at the rates listed on the label, especially since the amount of chemical is lower than recommended if you buy and mix the chemicals separatly. I tried a seaon with premixes and had many angry customers. I have since switched back to mixing the chemicals myself. The I know several franchises only use premixes I have talked to their employee's they usually use 50% more per tank than what the labels say to use they say it doesn't work well otherwise


LawnSite Bronze Member
There are a number of things that can effect the outcome of your results. First be sure you are using professional strength chemicals, make sure they are not diluted by freezing , I would also recommend using a spreader sticker. This allows the weed control to adhere better to the plant. Timing of the application is also important in relationship to the growth cycle of the targeted plant . Some weeds won't hardly die during the Summer months because they are hardly growing at all. Some 3-way herbicides are not very good at anything but dandilions and chickweed. Try something like Momentum or Super-Trimec. You have to be careful with the S-T , because at higher temperatures it can volitize and cause unwanted damage to ornamentals. Good-luck.

kickin sum grass

LawnSite Senior Member
cincinnati, ohio
ok, I will give you my two cents but you will have to take it in payments.

Here is what I found out as I was experimenting with spray rates. herbicides only. Anything over 2 gal / 1000 seemed to get lesser results as spray rate went up. I believe the problem is that plants over a 1000 sq ft can only hold so much water before it runs off so at 3 gal you maybe overwetting the grass and weeds and some of your herbicide maybe running off making your effective ai/1000 inadequate. I would suggest keeping your rate at 2 gal or less. We spray at 1.5 gal /1000 and get good results. To do this you must calibrate your sprayer to do so. That also includes changing your gun tip to a lower volume nozzle. I forget what the colors are but I am thinking the yellow one is what you need. then you can adjust the pressure accordingly.
You don't have to soak every leaf down. That could be your problem. With a rate of 1.5 gal, your spray will be hotter than at 3 gal. This means that more spray will be in each droplet of water. You can get good results with lightly covering the weeds and sometimes only wetting part of them down as you will be delivering the same amount of AI to each plant. This would be better than having run off and losing part of your spray.
Hope this helps


LawnSite Bronze Member
Stratford, CT

Your observations are correct. In general, the best weed control is had somewhere between .7 - 1.5 gallons of water per 1000.

The higher output nozzles do work better for thatch dwellin insects like Chich Bugs. They also work better for some fungicides on some disease especially those that are in the crown of are soil borne.

But postemergent herbicides are foliar absorbed (IN GENERAL) so the portion that falls past the targetted leaves is pretty much wasted. Thus the less than ideal efficacy when using high volume.


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