I've been trying to find a way to regenerate some topsoil on poor land without hauling in a lot of organic materials.
I'll give a bit of backstory. In 2015 my family moved into a newly built home in the suburbs of a small city. The builders had scraped all the topsoil off of what was previously a pasture, and piled it up. They built the homes in the subsoil as here in Canada we need basements to keep the, frozen in winter soil from shifting the foundations. Rather than replacing topsoil they placed sod directly on the subsoil. They screened and sold the topsoil for further profit.
I now have a small lot with difficult to grow lawns, almost no soil for any plants to grow and poor water retention.
Recently I started really thinking about a way to generate some soil, but I don't want to haul in large amounts of compost and would prefer an on-site solution.
I needed organic material, something I could grow and use for mulch and compost myself.
I was trying to find a plant with the following characteristics:
- Grows ok in poor/little soil
- Produces a large biomass
- Wouldn't become invasive (annual)
- Had somewhat woody, fibrous stalks to support fungal growth.
- Could absorb minerals and nutrients in plant available form
- Has a large root mass.
The one plant I came up with that best met these criteria was sunflowers.
It's winter here now so my plan will need to wait until spring but I have a plan.
Around the last frost date (May 20 according to the Farmers Almanac) I'll be sowing several rows of sunflowers around my house where there is enough sunlight to grow them.
I'll mulch around them after they sprout to keep it looking fairly tidy.
In the fall I'll have plenty of seeds for roasting as snacks and a huge pile of stalks and leaves.
The Plan
I have a small mulcher like the one above. so I figure I'll mulch up the leaves and stems to prepare them for composting. Originally I was going to use some of this material as mulch as well. However I recently learned that sunflowers produce compounds that can interfere with or even kill other plants. Used coffee grounds have similar properties before composting but are useful after composting so I'm 90% sure sunflower will be the same. In a Canadian Winter its hard to keep the worms fed all winter so even if the compost isn't great at least the sunflower trimmings will be easy to store and feed over winter.
Feasibility Testing
So I had 2 mammoth type sunflowers growing in summer 2018 that my son brought home barely sprouted as a Mother's Day gift for my wife. By the end of summer they were big, but not for a mammoth sunflower.
When I knew they weren't going to grow any more, I cut them off close the the ground and ran them through the mulcher (video below). My reasons for leaving the roots in the soil are:
- Not to disturb microbes in the root zone
- To continue as food for the microbes
- Once rotted to provide air and water channels into the soil.
After mulching the stalks they made a fairly decent feeding for my worms. The worms consumed the almost gallon of the shredded stalks and leaves faster than I'd expected. The feasibility of creating good casting to feed back to the soil seems good.
When I plant the sunflowers I'll add a bit of basalt rock dust just to help overcome any potential mineral deficiencies there may be in my existing soil. Sunflowers are great at accumulating minerals so when the casting is applied back some minerals should go back in plant available form.
In Conclusion
My plan at this point seems to be feasible enough to continue with in the spring. I'll be bringing updates over the next year at least.
I found this guide to cover crops, and thought it might be helpful to you. https://www.johnnyseeds.com/growers-library/farm-seed-cover-crops/cover-crop-decision-making-5-steps.html
Thank you, I really appreciate it
Interested to find out how your experiment is going. I tried something similar, with very little soil prep, and a pound of seed produced 3 sunflowers, a foot tall each. Hopefully you had better results!
I didn’t get as many planted as I wanted to. The ones I did get planted are starting off well. Looks like I won’t get as much fodder as I’d hoped though.
It’s good to hear that some of your seeds did what they were supposed to do. Thank you for the update.
Thanks for this. I have a quantity of powder that I had ground from sunflower seeds to add to my worm chow mix. It was at that point that I learned about the herbicidal qualities of sunflowers. I’m not going to feed it to the worms if there’s the possibility of the herbicide passing to the garden and wiping out plants. I would be very interested in your continued research.
I’m very confident that the composting process will nullify the effects of sunflower on other plants.
Hi Larry. I’m in Saskatoon & I’ve got a similar problem, I’ve bought a property where the yard was severely neglected & the lawn is probably 60:40 weeds to grass ratio. (90:10 when I bought it). I’ve been keeping it severely mowed to allow the grass to spread & choke out the weeds without resorting to chemicals, but the tilth underneath is pretty scarce. Did you rototill the area you planted your mammoth sunflowers last year, or directly into the lawn?
I planted them this year along the foundation of my house. There were only 2 planted in 2018. These 2 got my wheels turning as a possibility for expanding and creating more compost without having to haul in organic matter in my SUV. I’ll probably grow about 4 rows along the foundation this year as well. Not much of anything grows there otherwise but I wont till. I’ll plant straight into the existing weeds/grass.