Seed bowls for revegetation
Seed-based restoration of habitat
Sowing seed to restore habitat is faster and typically less expensive than planting seedlings. And it’s easier to scale-up and cover large areas. But lots of seed is lost to predators (particularly ants and birds), and it is tricky to actually get the seed to germinate and grow into a plant. Most sown seed, possibly 90% (1), will not become a plant.
These “seed bowls” are designed to improve the success of seed-based restoration on Raakajlm. They’re modelled on emu poo. Why? See this emu poo post. The seed bowl matrix will improve moisture-holding and soil microbiota at the germination site.
A recipe for making seed bowls
Let’s get straight into it! Here’s the recipe:
400g compost (no chunks)
130g worm castings
120g biochar
60g diatomaceous earth
30g psyllium husk
400g calcium bentonite
480mL (approx.) of liquid (My current liquid mix is: 120mL TerraMend Agricultural, 60mL Fulvic Acid, 300mL water)
You’ll also need:
30mL spoon for the mould
Water-holding crystals
Seeds - A Wattle and Pine mix is easiest, but I’m also trying grass seeds and everlasting daisies
Method
Mix the dry ingredients together. Add the liquid to form a crumbly dough that holds together when compressed.
Put a sprinkle of seed into the spoon. Fill with loosely packed “dough” mixture and sprinkle with water-holding crystals.
Use your thumbs to press the mixture into a bowl-shape, using the spoon as the mould.
Using the ball of your thumb and working from the edge of the spoon, push the bowl out of the spoon.
Dry the bowls upside-down for a day or so. This makes them less fragile, ready for dispersal.
Place them in the bush, seed side down. You can nestle them in a divet. When it rains, the bowls flatten out to form a replica emu poo and the seeds grow (hopefully).
Where to buy the ingredients for seed bowls
Compost, worm castings, biochar and water-holding crystals are readily available from any garden centre, including Bunnings. Diatomaceous earth can be purchased online, or from some pet stores like Pet Stock (it’s used as a natural insecticide for chooks). Psyllium husk from the supermarket (health food aisle). The calcium bentonite is a bit tricky, but you can ask at the special orders desk at Bunnings for “RichGro Bentonite - natural sand to soil”. They should be able to order it in for you. (It’s the easiest way to get calcium bentonite, rather than the more common sodium bentonite which isn’t suitable for seed bowls).
The TerraMend Agricultural and Fulvic Acid I’m using come from Best Farming Systems. To be honest, I’m still learning about what activators like these can do for soil health and boosting micro-organisms. Last year I used Neutrog’s “GoGo Juice” (from Bunnings).
Finally the spoons. We eventually found some 30mL ladles from a catering supplier (online example). Phil shortened the handle and bent them into a spoon shape. They work really well. Make sure your spoons aren’t too deep.
Do seed bowls work for restoration?
The seed bowls are placed out in the bush, seed side down and water crystals up. When it rains, the water crystals swell and the bowl flattens out. The bowl “dissolves” into the earth quite quickly, providing (theoretically) the perfect conditions for a germinating seed - moist and lively with beneficial soil biota.
The major recruitment bottleneck in our semi-arid climate is moisture availability. When I tested seed bowls in the bush in 2022, my experiment was confounded by La Nina high rainfall. Lots of little germinants emerged from the bowls. But, will they work in a normal or low rainfall year? And, are the seed bowls better than just putting a pinch of seed in the ground? Dunno.
This year, Year 8 students from Carey Baptist Grammar are making seed bowls and laying them out in a grid, interspersed with pinches of buried seed. Here’s a recording of a radio interview about this program.
I’ll be monitoring these plots to evaluate if seed bowls are more successful than just putting seed in the ground. Are they a “restoration game changer” or just a “flamboyant, charismatic, yet unproven technology”. (Highly recommend reading this article: Pedrini (2023) Drone seeding and E-seeds sound exciting, but ecosystem restoration needs practical solutions. The Conversation).
So what’s the back story? Seed bowls are a combination of two seeding methods, seed balls and seed pellets:
Seed balls
The seed ball planting method was popularised in the 1970s by farmer and philosopher Masanobu Fukuoka in southern Japan. The balls are a simple mixture of clay, compost and seed: “a universe in themselves”. Recipes vary, but generally call for 1 part red (terracotta) potters clay to 1-2 parts (or more) compost, with water to mix. Seeds are incorporated to make balls about 2cm in diameter. Hand-rolling is a fun activity for all, but larger quantities are made using a tumbler, like this one powered by a bicycle ridden by Costa! The seed balls are easily made but you can also buy beautifully presented, ready-made seed balls online. The balls are broadcast by hand, dropped from an aeroplane, or thrown over fences as guerilla gardening.
But, to be honest, I’ve had limited success using this technique in the Mallee. The balls I’ve made baked in the hot sun and I was still finding them, intact, years after spreading them. Like little rocks …
Seed pellets
There is a lot of research underway in Western Australia to enhance native seed-based restoration. Seeding technologies include seed treatments (to overcome dormancy and stimulate germination), and seed coating (covering the seed with product to improve the germination microsite). Seed coating ranges from a thin film on a single seed, through to extruded pellets containing seeds embedded in a matrix of various soil or organic-based products. Typical pellets are 8mm in diameter and 15mm long, but can also be flat discs like I’m making.
Ingredients for extruded seed pellets vary, but generally include:
clays - typically calcium bentonite like I’ve used here
binders - usually polymers such as celluloses and gums to stick things together - I’ve used psyllium husk
fillers - these are the soil matrix and include the compost and worm castings
active ingredients - I’ve used biochar (a type of charcoal), diatomaceous earth (soil amendment and essential minerals), TerraMend soil activator and fulvic acid. These should stimulate germination and get the seed off to a good start.
I could go on about how very clever this developing seed technology is … perhaps another day. For now, here’s a list of resources that informed my current seed bowl recipe:
Further reading:
Erickson et al. (2023) Unpacking the recruitment potential of seeds in reconstructed soils and varying rainfall patterns. Australian Journal of Botany (online early)
Erikson et al. (2019) A case study of seed-use technology development for Pilbara mine site rehabilitation. Mine Closure - AB Fourie & M Tibbett (eds)
Madsden et al. (2018) Inducing rapid seed germination of native cool season grasses with solid matrix priming and seed extrusion technology. PLoS One, 13(10), p.e0204380
Pedrini et al. (2020) Seed enhancement: getting seeds restoration-ready. Restoration Ecology 28(S3):S266-S275.
Ritchie et al. (2020) Developing extruded seed pellets to overcome soil hydrophobicity and seedling emergence barriers. Ecological Solutions and Evidence 1(2)
Stock et al. (2020) Field-Deployed Extruded Seed Pellets Show Promise for Perennial Grass Establishment in Arid Zone Mine Rehabilitation. Frontiers in Ecology and Evolution 8:576125.