2 Less-Known Methods To Improve Soil Fertility
In part 1, I talked about how organic matter is the most important ingredient for many gardens, and how mulch and compost are two of my favorite ways of using it.
But there are two other ways of using organic matter. The first is in some ways the most powerful of all, and the second may play an important role in reversing climate change. Let’s get into them…
The third way to use organic matter is to plant a cover crop, often done in the fall to be grown until spring, or sometimes interplanted among food plants such as in an orchard.
A cover crop creates air in the soil when the roots grow and die, grow and die again. Sometimes a specific crop that’s especially good at breaking up hardpans is used, such as certain radishes, and more often grasses and legumes are used.
Cover crops hold onto water and nutrients that would otherwise leach down out of the topsoil if there were no plants there. They also provide food and habitat for soil microorganisms, many of which would die off or go dormant without plant cover.
And yes, when returned to the soil as a mulch, or used in the compost pile, they become food for the soil. Cover crop seed is relatively inexpensive to buy, and the many additional benefits a cover crop brings make it in some ways an even more powerful organic matter source than mulch and compost.
The fourth way to use organic matter is with biochar. The ‘char’ refers to ‘charcoal’, which is made when you burn carbon-rich material such as wood at a high temperature, generally without the presence of oxygen.
Biochar, then, is basically charcoal that’s been made in a biologically sustainable way – made with non-toxic (and hopefully non-gmo) materials, from plants that wouldn’t have been better left alive and growing, created in a sustainable way, and generally used as a soil amendment to increase the carbon in the soil.
We’re in the early stages of learning how to do this well. Biochar is in most ways not as beneficial for the soil as good compost. It doesn’t contain the wide array of nutrients, isn’t a source of beneficial microbes, and doesn’t moderate soil pH – it actually has a high pH that can cause soil nutrient imbalances even more than compost.
But it is an excellent habitat for soil microbes, holds water and nutrients, improves soil structure, and is comprised mostly of very stable carbon that can stay in the soil for a thousand years, which means biochar could end up playing a very important role in reversing climate change.
In summary, if I could only do one task in my garden, I would bring in some form (or hopefully multiple forms) of organic matter – as mulch, compost, cover crops and/or biochar – in order to give plants and soil organisms access to more air, water and food.
In a couple of days, I’ll talk more about where the 80-20 rule falls apart in the garden (update: here it is).
For today, which methods of organic matter make the most sense for your garden? Do you have any questions on what we’ve been talking about?
Let me know down below…
Hi Phil, this is somewhat off topic, but I have a problem and don’t know where else I can get the info so I hope it’s ok to post here. I have planted some organic strawberry plants along one side of my house foundation and we have a pesticide company that comes and sprays a few times a year (unfortunately my DH doesn’t want to stop this practice) I had planned to move them this spring and didn’t get to them before they sprayed. I spoke with the tech from the company and he assured me that he recognized the plants as food so he didn’t spray in that bed but he did spray on either side of it. He also told me that the chemicals he used (although i didn’t ask specifically which he used) are systemic but I didn’t have to worry. I’m not sure I agree. It’s heartbreaking because I have tinkered with growing some food plants before and haven’t had much success but these plants took off and are producing the most gorgeous strawberries! but I don’t feel like I can even compost them or feed them to the animals safely. I was wondering if I just wait til they go dormant if I could move them and maybe in a couple of seasons they would be safe to eat? I probably should just start over with new plants but it’s hard to find organic seedlings around here. So this got me to wonder about the cycles of plants and if they “recover in time” from being contaminated or is that not possible? ANY info would be greatly appreciated!! Thank you for all the incredible info you share! Jill
Hi Jill, how long the pesticide stays around for depends on which pesticide was sprayed and the health of the biology in the soil that should eventually break it down. Some systemic pesticides can last in the soil for quite a long time – more than a year. As for how much chemical will make it into the strawberries, that’s really hard to say. Personally, I would wait until next year and then eat the strawberries, but that’s just me. You can decide when you feel comfortable eating them, but I would definitely leave them in the ground.
Thanks Phil I appreciate you getting back to me so quickly.
Thanks for offering the light version of the course Phil! It’s a perfect fit for my schedule and for what I want to do in my garden this year. I’m joining tonight! Will it be possible to “upgrade” to the full course at a later date?
I see you’ve joined Rod – welcome! Yes, email me whenever you want to upgrade.
I make my own compost and try to collect the leaves in the autumn, but I’ve been thinking that cover crops make a lot of sense. Seems to me it’s like making your own mulch with extra benefits too.
Absolutely right.
As far as cover crops go I’ve heard of perennial, such as white clover, and annual, such as legumes or rye grass. I am concerned that a perennial will end up being more a pest than an ally. What are your thoughts on this Phil?
Yes, a perennial mostly makes sense when you plant to leave it there, such as in an orchard. Annuals make more sense in a vegetable garden.
I’ve been working on making biochar on my own. I’ve put pieces of hardwood into terra cotta covered the top with terra cotta drip tray and put the entire thing into my wood stove and heated my house as usual while making the char. It seems to be working well. Does this method sound like I’m creating the right char. I guess I don’t know the difference between activated and not activated char. Can you help me clear that up?
I think there are a couple of definitions of “activated” char floating around. Technically, it’s char that has been processed in such a way as to have a much greater surface area. I’m not sure if a home fire will reach the temperatures required to do that. Perhaps someone will read this who can offer more insights.Other people refer to “activating” their biochar by combining it perhaps with fertilizers and especially with beneficial biology, using compost or microbial inoculants. That’s certainly a very useful practice for you to be doing with your biochar – whether or not “activating” is the terminology we should be using, I’m not sure.
Hi Phil, A few months ago I joined an organic community garden, in addition, this is my first attempt at gardening and I love it! My question is: I was considering collecting the autumn leaves this year to use as my organic supplement. Is there a right and wrong way to do this? My garden is a raised garden bed- 16’x6′ Thank you for any feedback.-Angela
Nope, there’s no right or wrong way. You can place them on the bed a a mulch this autumn and if there are extra, put them in a pile so they’ll turn into highly-prized leaf mould that can be applied next spring. No need to do anything else.
Hi PhilThanks for the great advice, I am beginning to work on improving the soil all around my property with mulch and compost and I just planted some cover crops. My goal is to create a food forest. I have extremely clay soil in a dry climate in Southern California. As for Biochar, I think I will hold off for now as it seems the jury is still out on how beneficial or potentially harmful it is. I think I need to learn more about it before deciding if I should apply it.Have you been using biochar and if so do you think your applications have been successfully?thxs Jim
I agree Jim, the jury’s still out, so no, I don’t use it – I stick with compost.
Hi Phil. You have mentioned using fallen leaves as mulch in a couple different places. Is it necessary to shred the leaves before putting on the garden beds? I don’t have a shredder; can I put unshared leaves on the beds without hurting the plants?
Unshredded leaves are great and indeed that means the mulch will last longer.