Liquid Grass Clipping Fertilizer

I'll be the first to admit that I'm a penny pincher.  I'm downright miserly.  I use organic, all natural, and permaculture growing methods because they are usually free if I produce the inputs myself.  There exists a wide array of options, but fertility management poses a problem in that these options can be somewhat limited, bulky, expensive if purchased or simply unavailable.  Have you seen the prices on bloodmeal, bone meal, azomite or greensand?  Chicken manure is rather spread out.  Urine is high in salts, has that heavy metal problem and presents a social stigma.  I'd like to try seaweed but I'm many miles from the ocean.  I've got a bull in the back field making manure every single day, but it can be messy and needs to be composted.  Compost and worm castings take a while and there are times when I could make good use of a natural fertilizer if I had it immediately.    I'm looking for a fertility treatment that can be had quickly, and be made with local, renewable materials.  Liquid grass clipping fertilizer looks to be the answer.  It is an all natural, liquid fertilizer made in a couple of days with locally available material using simple equipment that can be applied to crops at any time without harm.  And the price is right.

The process is simple enough:  mow some grass, add the clippings to a bucket, fill the bucket with water.  Let it steep for a few days.  This makes a tea from the grass clippings. What's happening is the mower has cut the blades, opening the vascular system of the leaves.  Water soluble nutrients bleed out of the grass and into the water.   Along with N, P and K are sugars, antioxidants, enzymes, proteins, trace elements, chlorophyll, organic and amino acids...the kind of stuff you don't get from commercial 10-10-10.  It's everything a growing boy needs.

I've done some pretty wierd stuff around here: stewing leaves in a slow cooker for a few days, putting manure in a blender, fermenting junk mail (don't do this), and composting old work boots.  This one is different.  It's easy, quick, makes sense, doesn't mess up the appliances, and most importantly, it is effective.  What's more, it can be scaled up or down to serve growing operations of any size.  The only inputs are grass clippings and water.  Equipment can be simple for small scale needs, and efficient for large capacity production.  You can make it on your kitchen countertop, or in buckets and barrels in your garden.  About the only way to screw it up is to let it steep too long.  This stuff will ferment, putting out a powerful stench.  If you are doing it right, there is no odor to disturb your neighbor's delicate noses. 

Let's make a 5 gallon batch
-Mow some grass.  If you have a bagger, life is easy.  If you don't, you only need to rake up enough to fill a bucket.  If you get some weeds, leaves, or soil in there, it's not a problem.

-Dump the clippings into a bucket.  2/3 full is the target.  Less than that the tea will be weak.  More and the grass will displace the water, you'll have less tea.

-Fill the bucket with water.  You can leave some room.

-Put a weight on top of the grass or add a lid.  Place in the shade.

The size of the bucket is not so important.  A smaller or larger container will work just fine as long as you keep the proportions about the same.   Understand that the grass is still alive.  In the first few hours the grass will suck up some of the water.  As it does, the density of the grass will decrease.  It gains buoyancy and will float.  The first time I made this stuff I filled the bucket.  The next day the grass had pushed itself out 6 inches.  It was a giant grass soufflé.  If the grass is not submerged you won't leach the soluble nutrients into the water.  You can put a lid on the bucket to keep the grass from pushing out of the bucket.  You can add a rock or plant pot on top.  A milk jug half full of water will do the trick.

Now you wait. 

Here's where it gets interesting.  The grass is still alive.  There will be some CO2 in the water.  The grass is still producing some oxygen.  Microbes on the grass and in the water will start their battle of fighting for resources.  They will start to grow and divide, being fed by the nutrients leaching out of the grass.  As long as the oxygen in the water holds out, the beneficial aerobic bacteria have the upper hand.  After a few days, the microbe population reaches a point where the oxygen is consumed faster than it is produced by the grass. The oxygen level drops, anaerobic activity becomes dominant and the batch starts to ferment.  This is where the smell comes in.  You don't want it to go that long.  If your batch goes too long and smells, throw it on the compost heap and start over.  It only takes about 3 days to get most of the water soluble nutrients out of the grass.  Make it quick.  Get in and get out.  Put the stuff to work.

If you want to put in a little extra effort you can splash the water before you add it to the bucket.  This can help to add atmospheric oxygen and CO2 to the water, giving you a little more time before it kicks off.  Each day, you can agitate the tea.  Give it a stir or dump the whole batch into another bucket.  The agitation will help move the nutrients out of the grass. 

Day 3-It's Ready

The tea should be a yellow to brown color.  The factors determining the color include temperature, how much soil went in, the species of grass, and what sort of inclusions were in there such as weeds and bugs.  You'll need to drain off the water.  The grass is finished.  You can still use it as a mulch, toss it on the compost, or offer it to the livestock.  I pull out most of the grass then pour the water through a window screen into another bucket.  This has the advantage of removing most of the seeds which may be present, particularly if the grass was high when mowed.  There can be weed seeds in there, so a filter may be desired.  For filtering, an old towel or cloth can do the job.  The screen I use has a frame.  I can set it on top of a bucket, lay a piece of t-shirt across it, then pour.  Once I give the steeping bucket a rinse, it's ready to use again.  If you filled the bucket initially with grass 2/3 full or more, the tea will be a little too strong.  It will need to be diluted with an equal amount of water.  Pour half of it into the just rinsed bucket, fill both buckets with fresh water.  You have doubled your volume and the liquid is ready to be applied directy to your plants.  You'll have from 7 to 9 gallons.


40 ounces, a quart plus a cup, applied per square foot would be the equivalent to a half inch of rain.  Doing the math works out to 3.2 square feet per gallon.  That 7 gallon batch would treat 22 square feet.  However, this is not rain water.  While this liquid fertilizer can be used for irrigation over wide areas, I think it is best used applied close to the root zone of the intended plants.  Put it where it is needed.  For a single plant, anywhere from a half cup to a quart will offer a fine boost.  I drag the bucket around with a big cup, pouring it around the stem until I see it starting to run off.  Potted plants can be offered as much as needed to moisten the entire container without draining.  7 gallons of diluted solution would serve a pint to each of 56 plants or a cup to over 100 plants.  A little bit goes a long way.

The liquid is more than just fertilizer.  It's an active biological aerobic tea.  As long as you mowed an untreated area of grass it can be applied to leaves, fruits and stems, serving a similar purpose as a compost tea albeit a weaker form.  The nutrients and organic compounds along with the mircrobes will add life and activity to the soil.  Your soil will come to life, your plants will thrive.  The nutrients are already in a form that is usable by your plants.  There is no delayed release.  Give the plants a couple of weeks to slurp up the goodies before reapplying.

There are several ways to apply this liquid gold.  Pour from a bucket, ladle it out, fill your watering jug.  Drip irrigation is possible.  Fill a milk jug, add some pinholes, set the jug where you want it to drip.  For commercial drip irrigation, the liquid will need to be well filtered as tiny bits can clog the drip tips.  Foliar spraying will also require adequate filtering.  Used in hydroponics, just pour it in.  If you have treated all your intended plants and growing areas and still have some left, apply it back onto the lawn where the grass came from.  Storing it might be possible with refrigeration, but this stuff is alive, it will go bad.  As simple as it is to make more, saving it is impractical.

Here Comes the Science

Fresh grass clippings have a C:N ratio of around 20:1, depending on the species, growing conditions, life stage and time of year.  They have an NPK rating of 4 - 0.5 - 2.  Lots of nitrogen in there.  Used as a compost ingredient, grass clippings can give a heap a tremendous temperature increase.

At Mother Earth News I found an article: Making Your Own Liquid Fertilizer by W.F. Brinton, PhD, founder of Woods End Laboratories.  It's a short article but it offers a wealth of information.   According to Dr Brinton, the NPK rating of liquid grass clipping tea is 1-.5-3.1.  It is also low in sulfates, salts, and sodium. 

In his paper Dr Brinton used a ratio of 10 to 1 water to grass clippings by weight.  At 8 pounds per gallon of water, a 5 gallon bucket batch would require 4 pounds of clippings.  I weighed some loosely packed clippings to find about 1 pound per gallon.  For 4 pounds of clippings, a 5 gallon bucket with grass pushed down to the 2/3 level would be consistent with this study.

Comparing to the fresh material suggests there is still a copious amount of N in the leftover clippings.  The compost will do well, but with some of the N leached into solution, I would expect reduced heating.  In a vermicomposting bin, the advantage is a food source that does not generate as much heat.  The relative amount of Potassium surprised me.  With such a strong K showing, this liquid should make an excellent contribution to root vegetables.  Used early in the growing season, it would promote development of a robust root system, giving the plants greater access to available soil nutrients, minerals, and increased drought tolerance.  Used late in the season, it would offer advantages for root and bulb storage as well as for overwintering plants.  P is nothing to write home about, but it's a viable source when other sources are few and far between.

Being most folks don't have a laboratory at home, getting the solution diluted to a level where it will not injure plants must be done with a qualitative method.  Look to the color and clarity of the solution.   If it is dark, dilute it more.  If you can't read a newspaper through 6 inches of liquid, dilute it more.  When in doubt, dilute it more.

Commercial all-purpose 10-10-10 fertilizer is typically applied at a rate of 10 pounds/1000 sqft.  A pint of water is a pound.  An equivalent amount of N in liquid grass clipping fertilizer would require 10 times the weight: 100 pounds (100 pints) per 1000 sqft.  This works out to 12.5 gallons/1000 sqft or 80 square feet per gallon.  Since 1 pound of grass clippings is used to produce 20 pounds, 2.5 gallons, of liquid grass clipping fertilizer, that 1 pound of grass clippings will treat 200 square feet.  These numbers suggest a very light application rate is all that is required.  Bear in mind, the liquid grass clipping fertilizer is not analogous to commercial 10-10-10.   These figures do not line up with the application rate discussed above.  Clearly, further experimentation will be needed to determine standard application rates, and these would then be dependent on each growers local conditions. 

Scalability of the Project

As long as the ratio of grass to water is kept the same, a liquid grass clipping fertilizer project can be tailored to any size required.   A balcony hobbyist can produce enough in a milk jug or 2 liter soda bottle to serve a few potted plants.  Just about anything that will hold water will be suitable for use.  A pair of scissors can trim and gather a handful of grass clippings.  That would be enough to produce a gallon.  Gather on Friday, use it on Sunday.  There is no rule saying the grass needs to steep for a full three days.  Using it earlier just means it won't be as strong.

I offer the 5 ballon batch as a standard size because the buckets are cheap, widely available and will hold up for years.  A full 5 gallon bucket will have a total weight of around 40 pounds.  Most folks can handle this size.  At least 2 buckets will be needed.  One bucket is used to steep the clippings.  One is held in reserve for decanting and straining.  Each additional bucket will serve to produce another batch.  With a 3 day steeping time, 3 buckets offers a batch every day.  Add one for straining, 4 buckets is all you need.  These things are 3 bucks each.  This makes it a $6 project to get started, $12 to make it an every day affair.

Keeping plastic pails out of the sun will increase their usable life.  Exposure to the sun will result in photodegradation and cracking of a plastic pail.  It will also warm the tea, promoting algae and bacterial growth.  When the algae and bacteria exhaust the supply of oxygen, the process goes anaerobic and will begin to produce a powerful odor.  The pH can change rapdily, as will the species of dominant microorganisms.  Keep it in the shade, use it at or before the 3 day mark.

Production on a larger scale suitable for use on a market garden can be done with a few buckets or move up to 55 gallon drums.  This is an order of magnitude larger than the 5 gallon bucket, but the process and ratios are unchanged.  Used drums can be found in the $10-20 range, or purchased new in the $70-90 range.  Looking at price per gallon, large sizes become more economical.  If drums are not available, there are trash cans and refuse containers which may be of service.  At 8 pounds per gallon, the sidewall pressures demand strength.  55 gallon drums are designed for containing liquid.  Getting into larger containers, the project becomes stationary.  Dragging an 800 pound barrel around a field is not going to happen.  A delivery system will be needed, but an operation which would require this sort of volume probably has an irrigation system in place.  It's a matter of straining the liquid and hooking in to the existing system. 

Volume is limited by the availability of grass clippings, water, and equiment.  While all of these can be had in most parts of the world, the fact remains that the nature of the solution demands it be produced and applied locally.  Storage is ill advised due to the time limit involved.  Transportation over long distances is impractical due to the volume and weight of water.  Nonetheless, for on site production and use, the ability to produce an effective liquid fertilizer cheaply and with simple equipment is hard to beat.


grass clipping tea

On the left is the water used.  On the right is the tea straight from the batch, run through a screen.  The center is full strength mixed with an equal amount of water.  It is ready to apply directly to plants. 



5 Ways To Fertilize Naturally



Ken Peavey's picture

this is comment test #1