Archive for August, 2011

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. 

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