May 2018 Tip of the Month: Leave the roots from your old garden plants in the ground to help feed soil organisms, increase soil organic matter, and grow healthier plants in the future!
We’re fortunate enough to live in Greenville, SC, a place where we can grow food year round – with a little extra effort in the winter months. Each season offers different crops, and it’s nice being able to tell what month it is by what’s on our dinner plates.
In addition to providing a steady stream of garden-fresh food for us, year round gardening means there are always living plants/roots in our garden beds which are providing a steady stream of food for soil organisms as well.
Yes, plants devote a significant amount of their energy to cultivating and feeding beneficial soil microbes via their root exudates. In exchange, those symbiont microbes help feed and protect the plants.
In nature, when a plant dies, there’s nobody to come along and yank it out of the ground, roots and all. Instead, the roots are slowly decomposed by soil microbes deep underground. Worms, bacteria, fungi, and other organisms all nibble away, ultimately converting the dead roots back into nutrients available for other living plants. And the cycle repeats. In the process, soil organic matter, soil carbon, and overall soil structure are all improved.
The above ground portions of a dead plant undergo a similar process of decomposition as the dead roots, although much more of the above ground material is volatilized into the atmosphere as it decomposes, rather than being immediately recycled into the soil. Also, the above ground portions of a dead plant will often play host to eggs of beneficial and predatory insects – and yes, some pest insects as well. (As we’ve detailed before, 95% of insects are beneficial or benign, so it’s important to learn to ID them and work with them.)
Why you should leave the roots from your old garden plants in the ground
What does this all mean? When you’re preparing your garden beds for a new season, don’t rip your plants out of the ground, roots and all. If you do, you’ll be robbing your soil microbes of a good meal and degrading your long-term soil fertility.
Instead, cut the plants just above the soil surface and leave the roots from your old garden plants in the ground as a food source for your soil organisms. If you’re not going to plant the bed immediately (ex: if you’re heading into a brutally cold northern winter) you can lay the above ground parts of the plant on the soil surface as a mulch, which also provides safe habitat for your overwintering beneficial insects/eggs. Or, if you want a “tidier” look, simply compost the cut plants before putting a layer of mulch down on the soil surface.
What about diseased plants?
Throw away or burn the above ground portions of any diseased plants that you’ve removed. As for the roots, the disease organisms are already present in the soil anyway, regardless of whether you remove the roots. You’ll want to top-dress the bed with compost or worm castings to introduce beneficial microbes, and be sure not to plant the same type of plant in that bed for a few years so as to starve the disease-causing pathogenic organisms of a food source (aka “crop rotation“).
Want to see these tips in action? Watch this video showing you how one of the best intensive, no-till organic farms in the country transitions between crops using the exact methods recommended above. (If you don’t want to watch the whole video presentation, just watch minutes 27-30.)
Questions? Ask away in the comments!