Building a Front-Mounted Boom Sprayer for Your Tractor

This post describes how we built our front mounted boom sprayer and how we adapted to get the job done after making some big mistakes.

Tractor with 3-point hitch rotovator and front-mounted spray tank on forklift attachment

We equipped our tractor with a front mounted boom sprayer to help get biology into our worn-out soil.  We wanted to apply beneficial microbes to our cover crop just before we rotovated (shallow-tilled) it back into the soil.  A tractor with equipment mounted in both the front and back accomplishes two operations in one.  We can spray in the front and rotovate in back (reminds me of the famous mullet hairstyle joke!), all in one pass across the fields.  This saves lots of time and soil compaction.

We were initially willing to purchase a front mounted boom sprayer, but we had an extra hard time finding one!  We looked at the specialized sprayers for orchards, but they were very expensive, and most of the tank capacities were less than 50 gallons.   We also saw front mounted sprayers for huge tractors, but there was no way our tractor could handle a 500-gallon tank.  We were hoping for a tank capacity around 100 gallons.   We saw plenty of 3 point hitch (for the back of the tractor) boom sprayers, but they were expensive too, and we’d end up taking off the 3 point attachments anyway.   

So we had an idea:  our tractor already has a fork lift attachment, so why not strap the tank onto that?  We bought parts – 100-gallon tank ($250), agricultural 1 gallon per minute spray pump ($80), and a boom with nozzles ($180).  We already had other materials:  electrical wire to run the pump switch into the tractor’s cigarette lighter, tie-down straps, flexible water tubing to connect the tank to the boom, etc.  This worked like a champ with water, and we were excited to get going.

Front-mounted spray tank - first design with spray pump connected to boom

The problem came with molasses.  We wanted to add some kind of sugar with the microbes to the tank.  Sugar wakes up the microbes and gets them going.  Molasses is highly recommended because it’s sweet and contains minerals.  What we would give to go back in time and pay more for liquid molasses instead of dry molasses!  Dry molasses is much cheaper ($18 per 50 pound bag), and it’s easy to get at farming supply stores.  It’s an animal feed, and this animal liked it!  It smelled really good and tasted like raisin bran.  We wanted to spray at least 5 pounds of sugar per acre, and the bag said dry molasses had 38% sugar.  We did a test rotovating run and determined each tank would cover just under 2 acres, so we added half a bag (25 pounds) to the tank with the recommended rate of microbes and filled up the tank with water. 

Well, the sprayer nozzles clogged within 5 minutes!  In our studying of the dry molasses bag to find the sugar content, we somehow missed the words in big font that said “22% FIBER”.  Once it was soaked in water, the residue was like oatmeal.  The nozzles couldn’t handle it, and the spray pump also clogged after we took the nozzles off and tried to just pump the mix out through the lines.

We were frustrated!  We were in a good weather window, and lots of rain was predicted to start in the next few days.  We started steeping the molasses in 5 gallon buckets and filtering it through a kitchen colander.  Took forever! 

Second design- note new flexible piping, valve, and pvc on top of tank

We couldn’t take the spray pump completely apart to clean it, so we opted for another route.  We weighed down a sump pump at the bottom of the tank and connected it to a ¾ inch diameter pvc pipe with holes drilled in it.  Since the sump pump put out way more than a gallon per minute, we put a valve in between the pump and the pvc pipe and partially closed it.  More liquid was coming out of the holes closest to the pump, so we wrapped tape around the pvc to partially cover those holes.  The liquid was now coming out pretty evenly along the whole length of the pipe.

Out in the field, the streams coming out of the pvc pipe worked just fine.  Not every leaf got coated, but since microbes multiply, this is probably not a big deal.   

In summary, the molasses fiber mistake cost us about $260.  We can use the boom, but the spray pump is probably a goner.  We will probably get another spray pump and hook it up to the boom for future use, such as spraying foliar fertilizers where we want a fine spray.  But for getting microbes and sugar into the soil, the cheap sump pump and pvc pipe was good enough.  We intend to keep learning – we imagine we need some sort of filter and agitator inside the pump, and we probably need different nozzles.  Unfortunately, we again learned the lesson to not trust the “agricultural” label, such as agricultural nozzles.  These are used to mainly spray pesticides and herbicides (clear liquids), and we’re not in that line of business, so we need completely different components. 


6 responses to this post.

  1. Posted by Rich on August 31, 2011 at 7:04 pm

    I’ve never sprayed a molasses mixture or designed a sprayer, but I have a little experience with spraying liquid fertilizer so some of my comment might or might not be relevant or helpful.

    If I read it right, you’re spraying 50 gallons of solution per acre, which seems like an awful lot to me. As a comparison, 10 gal. of 28% fertilizer has about 30 lb. of N, so if you only want to spray 5 lb. of sugar per acre you should be able to easily dissolve that amount into 5-10 gal. of water (assuming the salts in the N and the sugars in the molasses have about the same ‘density’, ‘solubility’, or whatever it’s called).

    And, if you are spraying 50 gal/acre instead of 10 gal/acre your pump pressure would also need to be a whole lot higher, which might be adding to some of your pump problems.

    Another idea is changing to some “streamer nozzles” (3-hole, 7-hole, or streamer bars) that are designed for applying liquid fertilizers and might work better for spraying a liquid molasses mixture.


    • Thanks, Rich! Hmmm, good question. I’ll need to ask my hubby, but I believe we sprayed 50 gallons per acre because we were tractoring SO slowly to get the rotovator to work right. My next post will describe that adventure. Our rotovator is 7 feet wide, so covering one acre takes a very long time. Thanks for the tip on the nozzles. Do you think residue the size of oatmeal would pass through? We’re trying to think of a good filter system to put inside the tank – maybe a big bag made out of cheesecloth.


      • Posted by Rich on September 1, 2011 at 7:06 pm

        I doubt if any nozzle will be able to handle something with the size or consistency of oatmeal. Nozzles come in a variety of sizes, but the 3-hole streamers I’ve seen have holes about 1/16 of an inch plus or minus.

        If it is possible to spray mixtures like compost tea or earthworm castings tea, it should be possible to use similar techniques to spray a solution derived from dry molasses.

        In the long run, it might be easier and take less time to extend your booms and spray the field at a higher speed and lower rate in a separate operation (filling up the tank every couple of acres has to take a lot of extra time).

        Did you notice any reduction in weeds in your field yet? This summer, I planted about 12 acres of sorghum-sudangrass after wheat harvest (planning on a hay crop), but the heat and drought stunted most of it’s growth. But, as a cover crop it sort of worked, because I’ve noticed that there isn’t a significant amount of weeds in that part of the field (so there might be something to those allopathic claims).

      • Thanks for the info on the nozzles! I talked to the Ag Verra company yesterday and found that I should not have used dry molasses meant for feed. I should’ve used freeze-dried molasses, which dissolves pretty well. About weeds, yes that’s interesting. The weeds, especially marestail and common ragweed, were going neck and neck with the sorghum sudan. Then when I mowed the fields, the weeds seemed to be gone for good. I’m wondering too about the allopathic effects of all the sorghum sudan mulch that our bushhog created. After mowing, the sudan and cowpeas both came roaring back with no signs of weeds expect for places where we missed planting. Also, it’s been 3 weeks since we rotovated now, and we see very little weed germination.

  2. Hello! It was so random to come across this post, as this exactly my idea, as we to are working in a series of cover crops over the course of year, and applying our compost tea.. I am in the process of figuring out the boom spray system, which we plan on carrying with the tractor forklifts.. would you be willing to drop an email and chat a bit more about your design??… (i know its spring time for us farmers, so if you don’t have the time, trust me, I understand!!)


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