Which Commercial Fertilizer is Best? 10


Which Bunnings Fertilizer is Best?

We purchased a range of “off-the-shelf” fertilizers from Bunnings and tested their performance.

Hungry Bin Worm Farm Worm Lovers

We think our Hungry Bin Worm Farm is great. It’s easy to use, the worms love it, and it produces plenty of worm wee.

This summer we conducted an experiment to test the performance of a range of potting mixes. While setting that experiment up, we expanded it to investigate a range of “off-the-shelf” fertilizers (mostly certified organic ones). For those of us limited to major hardware chains and local nurseries, these are often the only viable ways to replenish the nutrients in our container gardens.

We compared nine different fertilizing regimes. All of them were purchased from “The Big Green Box” and covered a range of powders, pellets and liquid feeds. We also used the home-grown worm wee that we obtained from our Hungry Bin Worm Farm.

ProductCostPackage VolumeCost Per TreatmentOrganically Certified?NPK RatioApplication MethodBatch Number
Fine Farms Blended Cow Manure$3.9525 Litres$1.58NoNot reportedMixed 50/50 (v/v) with potting mix prior to potting upN/A
Osmacote Plus Trace Elements: Vegetable, Tomato, Herb & Garden Beds$6.88500g$0.14No9:1:42 teaspoons mixed through 6 litres of potting mix prior to potting upN/A
Richgro Mega Booster Fruit and Citrus Organic Fertilizer$13.375kg$0.05Yes6:1:24 teaspoons mixed through 6 litres of potting mix prior to potting upN/A
Rooster Booster$16.4620kg$0.17Yes3:2:21 handful mixed through 6 litres of potting mix prior to potting upN/A
Charlie Carp Organic$10.681 Litre$0.96Yes3:1:290 mL per watering can (9L). applied to foliage and soil every 2 weeksBatch No 51 (10/06/15)
Dynamic Lifter Liquid$12.981 Litre$0.52Yes7:1:41 Cap full (40mL) per watering can (9L) applied to foliage and soil every 2 weeksYS1620029 (08/09/16)
Home Grown Worm WeeN/AN/AN/ANoN/A1 Litre per watering can (9L) applied to foliage and soil every 2 weeksN/A
Seasol$34.634 Litres$0.26Yes0:0:430 mL per watering can (9L). applied to foliage and soil every 2 weeks372SR15084 (06/07/15)
Seasol and Charlie Carp Organic MixN/AN/A$1.22YesN/A30 mL Seasol + 90 mL Charlie Carp Organic per watering can (9L) applied to foliage and soil every 2 weeksN/A

Each treatment was used to try and improve the plants growing in two different types of potting mix. Earthwise Multipurpose Potting Mix was the cheapest potting mix we could find. The Bulk Potting Mix from, Fulton’s Garden Supplies, what we would consider an “average” quality potting mix and was the second potting mix we aimed to improve with the fertilizers.

Setting up the fertilizer experiment

Which is the best organic fertilizer from bunnings

We mixed the powdered and pelletised fertilizers through the potting mix prior to potting up.

For both the potting mix and fertilizer experiments, we used capsicum seedlings. These were all relatively the same size, in the same condition and appeared to have been sown at the same time. We potted up five seedlings in each of the different potting mix/fertilizer treatment combinations. We tried to make sure that each soil had a seedling from five different punnets to reduce the chance of experimental error. Any powdered and pelletised fertilisers were mixed through the potting mix prior to use. Liquid fertilizers such as Seasol and Worm Wee were applied immediately after potting up and then every fortnight thereafter.

The potted-up seedlings were then placed in our greenhouse. The pots were alternated to ensure that the five pots for each of the soils were spread across the shelf. Each pot appeared to have equal access to light and water. The automated irrigation system watered every morning with a fine mist for 5 minutes. After six weeks, we assessed the plants and took photos of the results.

Results of the Fertilizer Experiment

We assessed each of the plants and recorded the colour of the leaves as well as the number of plants in each group that had set fruit. We also recorded the total number of flowers and fruit set on the 5 replicate plants combined. See the results tabulated below.

Results of different fertilizers used to treat seedlings growing in the Fulton’s Bulk Potting Mix

FertilizerColour of LeavesNumber of Plants With FruitTotal Number of Fruit across the five plantsOther Comments
Negative Control (No Fertilizer, potting mix only)Light Green0/50 One flower present, but no fruit. One plant showing evidence of disease.
Fine Farms Blended Cow ManureLight Green2/54
Osmacote Plus Trace Elements: Vegetable, Tomato, Herb & Garden BedsDark Green3/551 plant died, probably due to transport shock or not receiving enough water. These plants were the largest and healthiest looking plants with plenty of flowers.
Richgro Mega Booster Fruit and Citrus Organic FertilizerLight Green2/53These plants were also some of the largest. Leaves were starting to turn yellow.
Rooster BoosterLight Green0/501 plant died, probably due to transport shock or not receiving enough water. Plants only slightly bigger than negative control.
Charlie Carp OrganicLight Green3/54Plants look similar to negative control.
Dynamic Lifter LiquidLight Green2/53Plants look similar to negative control.
Home Grown Worm WeeLight Green0/50Plants look similar to negative control.
SeasolLight Green0/50Plants look similar to negative control.
Seasol and Charlie Carp Organic MixLight Green0/50Plants look similar to negative control.

Results of different fertilizers used to treat seedlings growing in the Earthwise Multipurpose Potting Mix

FertilizerColour of LeavesNumber of Plants With FruitTotal Number of Fruit across the five plantsOther Comments
Negative Control (No Fertilizer, potting mix only)Yellow0/50
Fine Farms Blended Cow ManureLight Green1/51
Osmacote Plus Trace Elements: Vegetable, Tomato, Herb & Garden Beds1 x Dark Green
3 x Light Green
1/52These plants look the biggest and healthiest
Richgro Mega Booster Fruit and Citrus Organic FertilizerLight Green0/53
Rooster BoosterLight Green0/50
Charlie Carp OrganicYellow0/54Plants look similar to negative control.
Dynamic Lifter LiquidYellow0/53Plants look similar to negative control.
Home Grown Worm WeeYellow0/50Plants look similar to negative control.
SeasolYellow0/50Plants look similar to negative control.
Seasol and Charlie Carp Organic MixYellow0/50Plants look similar to negative control.

We also took photos of the plants. Below are images of the best plant out of the five replicates for each fertilizer type. As you can see there is a huge variation in the performance of each of the potting mixes.

Results of different fertilizers used to treat seedlings growing in the Fulton’s Bulk Potting Mix

Best Fertilizers from Bunnings

The best plant from each of the 5 replicates. These plants have been planted in Fulton’s Bulk Potting Mix and treated with our selection of “off-the-shelf” fertilizers.

Results of different fertilizers used to treat seedlings growing in the Earthwise Multipurpose Potting Mix

Best Fertilizers from Bunnings

The best plant from each of the 5 replicates. These plants have been planted in Earthwise Multipurpose Potting mix and treated with our selection of “off-the-shelf” fertilizers.

So what do the results from our Fertilizer Experiment all mean?

Well, first there was a huge difference in the responses to fertilizing regimes shown by plants growing in the Earthwise Multipurpose Potting Mix vs the Fulton’s Bulk Potting Mix. It seems that even with the best quality fertilizers, terrible soil is difficult to improve.

The other notable result was the difference in performance between the liquid fertilizers and the powdered/pelletised fertilizers. In our experiment, the liquid fertilizers performed far worse than the powdered/pelletised fertilizers. I suspect that in this experiment, it had a lot to do with the automatic irrigation system. This delivered water to the plant in excess of their requirements. This likely flushed nutrients out of the potting mixes. Liquid fertilizers are promoted as having soluble nutrients that can readily be taken up by plants. Because they are soluble, they are probably also readily flushed from the potting mix faster than the powdered/pelletised fertilizers.

For those of you with container gardens, you are unlikely to be watering your plants as frequently, or with as much water as in this experiment. The use of saucers under your pots will also help to retain nutrients and allow them to be taken back up into the potting mix. It would be interesting to see how the liquid fertilizers perform under these “more normal” sorts of conditions.

The best performing fertilizer was clearly the Osmocote Plus Trace Elements: Vegetable, Tomato, Herb & Garden Beds. However, this fertilizer is not certified organic. If you re after a certified organic fertilizer, then the Richgro Mega Booster Fruit and Citrus Organic Fertilizer is the best performer in our opinion. We would always encourage growers to improve their soil using home made composts. But for those of you with limited space, these products may be suitable for you to try.

On 01/05/17 we contacted the following manufacturers or suppliers of each of the products investigated:

We invite them to leave feedback on our experiment in the comments section below. We’ll look to repeat this experiment again in the future and would appreciate feedback from the public on how it may be improved to obtain even more meaningful results for our readers and gardening community.

Disclaimer: All of the products tested and materials used in this experiment were purchased by Leaf, Root & Fruit at full retail price. No incentives or sponsorship are received from any of the companies mentioned in this blog post.


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10 thoughts on “Which Commercial Fertilizer is Best?

  • David

    Love this article and the one on potting mix. Very informative. I’ve used a number of fertilisers in the past and have found that Brunnings and Osmocote were the more consistent performers. Brunnings is much cheaper but unfortunately do have higher than recommended levels of heavy metals.
    I use Seasol more as a plant tonic rather than fertiliser. There’s not much nutrient once diluted at the recommended level.
    But awesome articles.

    • Leaf, Root & Fruit Post author

      Thanks David. Glad you’ve found it useful. Seasol is indeed more of a tonic than a fertilizer and I included it more so to highlight this fact.
      Happy Gardening!
      Duncan

    • Leaf, Root & Fruit Post author

      Hi Steve,
      Thanks for your feedback. Glad you enjoy our work. What do you mean by doing “combined experiments”? We combined two products (Seasol and Charlie Carp) as I knew that Seasol was not considered a “fertilizer” as such, more of a tonic and was interested to see the results of combining it with a more nitrogen rich source. Is that the sort of thing that you would like to see more of? We’d love to do further trials and test as many combinations as possible, but in the end it comes down to time and budget. As it was, the potting mix and fertilizer experiments this summer cost us several hundred dollars in materials alone. Once you start expanding to combinations, then the number of replicates goes up exponentially and so do the costs!

      Happy Gardening!
      Duncan

  • Graham Smith

    Hi Duncan
    You have gone to some serious effort with your experiment, for which I congratulate you, however there are a couple of things I wish to point out. Seasol, as you state in your article, is not a fertiliser, but more a plant tonic, and it has amazing effects on the root growth of plants, whilst at the same time assisting in their ability to cope with a number of stresses.
    In your field showing NPK, you actually list Seasol as having 10:1:18, which is completely incorrect. Seasol has virtually no N, or P but has around 4 in K, plus an array of trace elements and plant stimulants.
    When observing your growth trials, you also correctly point out that the irrigation was probably more than normal, which will indeed leach out the nutrients of liquid fertilisers, again which is why the dry products performed better.
    One of the most important facets of growing is of course the medium in which plants are planted, which is why potting mixes have red ticks for premiums and black ticks for standard. There are minimum requirements for both and they relate to what is in the potting mix and how long a plant survives and thrives.
    One of the most important parts of growing, particularly vegetables, is the preparation of the soil, which is why it is important to incorporate organic material along with other materials to ensure good drainage and healthy root growth.
    On our website you will find footage of our root assays which shows root growth in a standard Seasol solution versus water.
    Seasol actually fires the plant up to go searching for nutrient, and if there is none there, the plant performs as shown in your trials.
    The sister product to Seasol is PowerFeed which is a fertiliser with added compost and fish (NPK 12:1.4: 7)
    PowerFeed is also now available in a granular which has freeze dried microbes to really get the soil humming.
    It would be great for you to trial a combo of all three, as I think you and your audience would be extremely impressed with the results.
    Once again, congrats on putting so much work into your trials. If you need any more information don’t hesitate to contact me.
    Kind Regards
    Graham Smith
    Seasol International Pty Ltd

    • Leaf, Root & Fruit Post author

      Hi Graham, thanks for your prompt feedback. I have updated the NPK ratio for Seasol accordingly. As you say, when growing vegetables it is important to prepare the soil correctly. By adding lots of organic matter and quality compost, then I believe we don’t need any of these commercial fertilizers. Given the huge positive response we’ve already had to this trial and also our previous potting mix trials we will no doubt look to conduct more trials in the future. I’ll certainly consider some of your other products that you’ve mentioned for these.

      Happy Gardening!

      Duncan

  • Pauline Webb

    May I comment from a home gardener’s view. I do a permaculture organic style garden in Doncaster East. It was a difficult summer, short and sharp, preceded by a late chilly spring. Tomatoes may have been easier to test as capsaicum are frequently a challenge. I obtain the best results, fruit wise, from plants which survive the overwinter temperatures, are pruned in spring then flowerquicker as the plant is already grown. Frequently capsaicum and cucumber don’t achieve much fruit until late summer into autumn. They often have weekly feeding of worm wee or seasol on top of compost and peastraw mulch.

    I did grow 2 capsaicum plants in Debco’s best mix with liquid supplement on my patio and they must have had about 6- 8 fruit each.

    Better luck next time

    Pauline

    • Leaf, Root & Fruit Post author

      Thanks for your feedback Pauline. We chose Capsicums as they are relatively small plants, so they don’t take up much room in the green house (compared to say Tomatoes). They require little care such as staking and don’t have much in the way of pollination issues (there’s not usually many bees in our greenhouse!). They also transplant well and can be fairly quick to flower and fruit – some of the better plants in this experiment flowered within four weeks of transplant. We prefer a fruiting plant over leaf or root crops as fruiting plants have more complex nutrient requirements. The capsicums really test out the overall quality of the fertilizer much better than say, lettuces which would really focus on the nitrogen content.

      Thanks again for sharing your experience with us.

      Good Luck and Happy Gardening!

      Duncan

  • Chris

    Charlie Carp
    Thank you for considering Charlie Carp in your trial process, it is a very good product that is both helping the environment and producing better gardens and lawns. I would like to make a few comments on your trial process:
    Firstly, as you note, you have compared certified organic fertilisers with fertilisers that are not certified organic. There is no organic fertiliser I am aware of that would have a level of nitrogen which could compete with non organic fertilisers (which provides that initial growth spurt and extra greening). Organic certified products will have longer term benefits for the plant and soil which non organic products do not have.
    Secondly the application of slow release fertilisers (dry) versus liquid fertilisers require slightly different methods of application. No initial watering is required for Charlie Carp. If water is applied this will dilute the effect of our product (which you have noted). We recommend that you do not use our product if it is about to rain and also do not water immediately afterwards. Dry/slow release products will require water to release the nutrients.
    As you would be aware we also have Charlie Carp Original which has a higher level of nutrients and is 100% natural. This would have provided a greater initial boost to growth if you had used that in your trial. Perhaps you could test that next time
    I look forward to you next body of work.
    Kind regards
    Chris
    Charlie Carp

    • Leaf, Root & Fruit Post author

      Thanks for taking the time to respond Chris. We’ll take your feedback on board and consider it for any future work that we do.

      Duncan