Green garden fertilizers

Would you sprinkle fossil fuels such as gas or oil on your vegetable patch? Would you rip up a beautiful landscape elsewere for the sake of adding a few nutrients to your front garden? Likely not, but without even knowing it, often that’s what we do with our gardens and crops when buying fertilizer.

The bigger, better, faster approach to agriculture and gardening has made millions of acres of land more desolate, impacted on our waterways and caused all sorts of other environmental havoc. It’s certainly not just large scale agriculture that’s to blame, the chemicals we apply to our domestic gardens and veggie patches often contribute as they come from the same sources.

We are now in a period of agriculture where greater amounts of energy required to produce smaller increases in crop yield, partly due to synthetic fertilizers destroying once fertile land.

Synthetic fertilizers tend to be quick release and the plants never get to use much of the nutrients –  which then wind up in our waterways. What the plants do take up promotes rapid growth which can deplete the plant’s stored energy reserves for hard times. Synthetic fertilizers discourage natural self-sufficiency and plants can wind up with a shallower root system as they become totally reliant on the fertilizer. It’s a little like drug addiction.

The big 3 fertilizer components

While fertilizers contain calcium, magnesium, iron and other trace elements; the major components in “all purpose” fertilizers you buy at the hardware store or nursery are primarily composed of nitrogen, phosphate and potassium. These are the nutrients that plants need the most of.


Nitrogen is required by plants primarily to promote foilage growth. As mentioned in my article on Fuel and Food, much of the nitrogen in fertilizers is gained through the Haber-Bosch process which utilizes natural gas – a lot of it. The Haber-Bosch process is used to create in excess of a hundred million tons of nitrogen based fertilizer annually. An incredible 1% of the entire world’s annual natural gas supply is used to generate nitrogen for agricultural and gardening processes.


Plants need phosphate to stimulate root development and flowering.

Phosphate is usually strip mined, crushed, then treated with sulfuric, phosphoric, or nitric acid to produce soluble phosphates that can be used as fertilizer. According to Associate Professor Cynthia Mitchell from the University of Technology in Sydney, Australia, the world’s deposits of phosphorus will be depleted in about 50 years.

Plants aren’t the only form of life that like phosphate. Over the decades, due to the overusage and nature of phosphates in synthetic fertilizers and detergents, increasing amounts have been entering into waterways, which spurs on the growth of algae and phytoplankton. These can grow at such rates and densities that sunlight is blocked and the water beneath the algal bloom is starved of oxygen; killing other creatures in the aquatic ecosystem. Some forms of algae are toxic in themselves and can kill humans if ingested.


Potassium is important to the overall health of plants – and for most creatures for that matter. Most of the potassium (95 %) produced today is used in fertilizers. It is gained primarily from mining.

You can see there’s a whole lot of destruction and energy consumption involved in the production of commercial fertilizers, not to mention the added resources used in packaging and shipping.

We’ve been using so much fertilizer that we’ve destroyed the delicate balance of the land. Plants become reliant on the synthetic stuff and as dependence grows, more needs to be applied. This cycle of using more to get back less from the land continues until the point the land can sustain nothing at all; it becomes toxic and barren.

It’s been a case of taking from nature more than it is prepared to give and now we’re paying the price.

We tend to do the same in our own gardens; using this product and that potion – simply because we’re told it will give us healthy, fast growing plants. Perhaps it does; but only in the short term. While our individual consumption of commercial fertilizers is only on a small scale compared to the agricultural industry, there’s millions and millions of us doing it and we’ll wind up facing exactly the same problems in our own yards in time. The issue of phosphate runoff from urban environments is already significant.

Natural fertilizers

The first thing I learned about a greener, more natural approach to fertilizer, much like with pesticides, is that more is not better :). By overusing fertilizer of any type, natural or synthetic, it’s quite possible to not only contribute to the phosphate runoff problem, but also to kill the plants you’re trying to care for by burning their roots or making them totally dependent on your intervention for their survival.

The other wonderful aspect about the “less is more” approach aside from minimizing environmental impact is that it saves you money. In fact, using green fertilizers can be incredibly cheap as many of the base materials are in, around, or close by to your home.

Commercial organic fertilizers

These are readily available, but be careful to read the fine print. In some countries, fertilizer labeled as organic only needs to contain a small amount of carbon based materials – the rest can be synthetic. Usually companies are required to note the percentage of organic vs. synthetic though, so look for these figures.


This is wonderful stuff – I used it on our vegetable garden in our last house. In fact, aside from a few grass clippings and leachate from our worm farm, it was all I used. If you live near the coast, you can collect washed up seaweed and either wash it to remove some of the salt or wait for the rain to do it for you (preferable – we need to save water). 

Then it’s just a matter of applying it directly to the soil. Due to its gelatinous nature, whole seaweed also helps to capture water and bind soil. If you can’t collect your own, it’s available as a liquid extract from most gardening centers and nurseries. Seaweed is an all-in-one fertilizer; it contains everything your plants will need.

Grass clippings/mulch

The best thing to do with grass clippings is to put them back on your lawn by not using a catcher when mowing; but if this isn’t an option, you can apply the clippings to garden beds. Be careful not to apply too much, particularly if the clippings are moist and very green as the natural chemical reactions during decomposition can create ammonia and make the soil below acidic.

Leave the clippings spread out in the sun for a day or two to dry or dig them into the soil to separate them. Grass clippings contain 3-4% nitrogen when dry, plus phosphorous, potassium and other trace elements.

Leaves you rake up and other small organic material from around the yard make excellent natural fertilizers and applying layer of organic matter (known as mulching) also helps the soil below retain moisture. Just be a little careful how much of any one type of material you use for mulching, for the same reasons as for grass clippings – the risk of acidity; particularly when using green materials with a high moisture content.

Animal manure

Horse, cow or chicken manure – all excellent natural fertilizers; although bear in mind that whatever chemicals were present in the animal’s diet may also end up in your garden.  Manures should be dug into the soil to conserve nitrogen. If just spread on the surface, they’ll lose much of their nutrient potential very rapidly. Fresh manure should be kept away from the roots of young plants as it can burn the roots. Humanure is also good, but that’s a whole different topic that I won’t attempt to address here so as to not put off the more squeamish :).

Wood ash

Have a combustion stove or open fireplace? Spread the ashes thinly on your garden and dig in where you can. Ashes contain potassium, phosphate and other trace elements.


Something I haven’t tried, but I’m told beer is a great natural fertilizer :). Instead of pouring those yukky dregs from the big night down the sink, try using it on your plants.

Coffee grinds/cold coffee

Sprinkle coffee grounds near your plants and dig them in a little. Coffee grounds can also be sprinkled directly on your lawn, and cold coffee is a ready-to-go natural liquid fertilizer

Compost or vermicompost it

Plants love compost; after all, good soil is just a mixture of minerals and naturally composted plant and animal material.

Since implementing a compost bin and worm farm, we’ve not only found the amount of garbage we send to landfill has greatly decreased, but we always have some sort of natural fertilizer on hand aside from what’s provided by our blackwater recycling system.

I’ve found the leachate that comes from our worm farm to be an excellent fertilizer and the castings (the solid end product after worm digestion) to also be wonderful stuff. It does take some time to build up a stockpile of castings wheras the leachate is continually available. Worm farm leachate is pH neutral, odorless and the plants just love it.

90% of our plant based kitchen scraps are fed to the worms, plus they enjoy chomping on newspaper and egg shells too. I highly recommend worm farms as a means of decreasing waste and converting organic waste into top quality fertilizer. There’s very little maintenance involved with keeping the little critters.

The compost bin has been good for grass clippings and taking care of our dogs doings, plus some other waste items worms aren’t too keen on. The key with a compost bin or heap is to ensure the contents are turned over regularly – particularly if you add a lot of grass clippings – again, let the grass clippings dry out a little if you can before adding to the bin. The turning over is something I regularly fail to do – the smell reminds me of the error of my ways :).

Soil checks

This is also something I’ve never had done, but I can certainly see the sense in it. If you’re unsure of the needs of your soil, have an analysis performed – you’ll then know if it tends to be acidic or alkalinic and what/how much of what you need to bring it into balance. An analysis can also help identify any nasties that may lurk in the soil which may preclude it from being safe to grow vegetables; such as the presence of heavy metals.

Using more natural fertilizers makes better use of waste from your own household and helps decrease the reliance on energy intensive and environmentally destructive commercial fertilizer production processes. It’s also a great feeling of accomplishment to see plants and veggies grow up strong and healthy without the assistance of the agricultural chemical industry.

And remember – always read and follow the instructions of any fertilizer you do buy; as more is not better. While it may not always be possible to avoid the use of synthetic chemicals, responsible use helps ensure less of a negative impact on the wider environment.

Have some tips you’d like to share on natural fertilizers? Please add them below!