Amy Draiss
Fall is a time to think about gardening jobs that may have been on the back burner while beds and planters were fizzing with dazzling ornamental color and cropping abundance. As more gaps appear in borders, rockeries, and patio arrangements, no doubt you’ve noticed the tell-tale signs that your garden soil is peaky and exhausted. With many bald and recently emptied patches groaning from diminished nutrients, structural disintegration and parched earth, you’ll be doing your garden the biggest service right now if you take time to amend soil in fall and give it a helping hand before the next wave of growth begins in earnest.
Autumn is the perfect time to invigorate your garden soil and get it ready for another frantic calendar year. Soil temperatures are still relatively warm, and you’ll have less resistance from the earth if you need to work materials into the ground. Added to which the quieter months of the year give slow-release organic fertilizers and compounds plenty of time to work their magic whilst many perennials, shrubs and overwintering plants are resting. Giving amendments time to get settled into the soil while the weather is gentler and conditions are quieter also reduces the risk of damage to tender plant roots.
Conditioning soil while things are relatively quiet and you still have some decent weather on your side also saves you important time in spring, when you’ll be wanting to get on with other things. But what are the best ways of amending soil in fall, you may well be wondering? Here are some of the best slow-release treatments, derived from a few easy and also a few less-obvious sources. They can all assist in restoring your garden soil’s balance, structure and fertility – so you can hit the ground running as the next gardening year rolls around.
Best Ways to Amend Soil in Fall
Knowing how to amend soil in fall doesn’t have to be complicated, nor does it have to be a chore. In fact, giving your soil a helping hand in autumn can be rewarding and enjoyable – yes, you read that right! I’m not kidding, I find the process of enriching and treating soil endlessly fascinating, from a broader appreciation of worms and beneficial soil organisms to a specific understanding of why certain soil amendments work so well – depending on when, and how, you add them. Making soil amendments in the fall is one of the best things you can do for your garden. And right now, you have time on your side. Things are a bit quieter, and making amendments now means your soil has plenty of time to deal with what you do next.
At this time of year, attention will naturally turn to your compost heap or bin, or any composting routine you already have in place, and that’s as it should be. However, for those of you looking to expand on your soil nourishing strategy, or just experiment a little with different methods of approach, this selection of amendments can all be added in the fall to help set you up for the best blooms and healthiest plants as you head into the new year. Just be sure to test the soil first, as it will help give you some natural pointers and direct your approach for these essential soil improvements. So roll up your sleeves and let’s get started.
Make sure you have a good grasp of existing soil conditions with the Raintrip 4-in-1 soil meter, which can gauge light, pH, moisture and nutrient load.
1. Worm Castings
If you’re lucky enough to have a generous supply of your own wiggly worms in the garden (in the ground or in a ‘worm farm’ composter), you may already be blessed with a good measure of these in the soil. Worms are synonymous with lush, healthy and organic composting. However, a top-up of worm castings or casts (soil that has been through the digestive tracts of worms) can work wonders for your garden gold on the way into fall. As a slow-release source of essential nutrients, worm castings (or ‘vermicast’) help to replenish beneficial microbes and bacteria, as well as assisting in the co-creation of that lovely crumbly structure.
This wondrous worm-worked concoction, worked into the soil in fall, also gives you a controlled release of essential phosphorus, nitrogen, potassium, sulfur and calcium. And as a helpful bonus, it delivers an effective pest control for aphids and spider mites, thanks to an enzyme it releases called chitinase. A vermicomposter like the Vego In-Ground Worm Composter (8 Gallons) from Walmart is a smart (and genuinely fascinating) way of churning out a fresh supply of worm-based goodness, including castings, for a nourishing topdressing for beds and borders.
If you are looking to hit the ground running right away, you can apply these organic amendments for soil in granular form. Highly rated Wiggle Worm Pure Organic Worm Castings from Amazon make exceptional topdressings while the soil is still warm. Simply apply above the root zone, and let this smart vermi-boosting fertilizer do its thing.
2. Bone Meal
Perhaps a little ominous sounding and not the most obvious place to go for soil health, the ground up bits of animals have a lot of natural goodness that your plants crave. Originating primarily from animal bones, this organic supplement is rich in calcium and provides a gentle slow release of phosphorus. Bone meal fertilizer is great news for any perennials and plants that are entering dormancy in your garden, as it helps wrap around roots and fosters healthy root development ahead of spring. Bone meal is an excellent boon for spring flowering bulbs that can benefit directly from this rich root-booster. It also works well for spring flowering shrubs, which can soak up the goodness in a steady way for optimal absorption.
These powdered fall organic amendments for soil are great for any root vegetables you are thinking of adding to a kitchen garden or raised beds, encouraging fast root growth that is robust and well branching around strong central tap roots. Try Back To The Roots Organic Bone Meal With Gypsum (12lb) from Amazon. Alongside bovine-based bone meal supplements, you can get fish bone-based fertilizers (bone-based amendments focus on phosphorus, while those that contain blood add nitrogen for a general-purpose top-up). I love sprinkling crushed fish bone into borders to give root systems a little TLC. Buy Down To Earth Fish Bone Meal (5lb Box) from Amazon. Mix into your compost, sprinkle over the soil surface, or work into the earth with a fork.
3. Cover Crops
Plants that actively improve the condition of your soil? Yes, please! It might sound too good to be true as light and warmth starts to dwindle, but there are still plants geared towards actively fixing soil deficiencies and nutrient gaps caused by overworked summer beds and borders. Cover crop plants replenish these nutrient gaps simply by dint of existing – and they also help to counter the effects of soil erosion, exposure to the elements, and compaction. Growing some of these proactive soil amenders in fall is a simple yet effective way to redress the balance underground ahead of spring – they are deeply low maintenance and seriously hard working, and some of them also look quite pretty, too.
Legumes like crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosa) and alfalfa (lucerne) are naturally adept 'nitrogen fixers' – they redirect nitrogen from the air into the earth via the roots. This is an effective counterbalance to other garden plants, which absorb nitrogen from the soil into their roots. Cover crops appreciate the cooler weather, and flowering types like Survival Garden Seeds Crimson Clover seeds from Amazon can service lingering beneficial insects that may still be tripping in and out of your flower beds. Just be sure to dig the plants into the ground before they self-seed. For a quicker-acting granular alfalfa treatment, buy Dr. Earth Alfalfa Meal from Amazon. Mix into the earth for a generous bump of core nutrients, a food source for soil organisms, and a gentle way to aerate particles and improve structure.
4. Bat Guano
This is perhaps not the most obvious source of goodness when you’re going about soil amending in fall, admittedly. After all, the chances of getting your friendly neighborhood bat to build up a ready supply of fertilizer would hinge on attracting them to your garden on a regular basis, to say nothing of gathering the stuff. And for those of you who aren’t familiar with the word ‘guano’ – yes, we are talking about bat poop. Still, there’s no denying that this unexpected organic soil amendment has a lot of natural clout. It works on a slow-release level when applied in the fall, nourishing the soil over several months to improve friability – which is a fancy way of saying that it works really well to bring about peak crumbliness in the ground.
Get your (gloved) hands on some guano (to prevent the risk of pathogen transfer), and either work into the soil or add as a topdressing. As regenerative gardening techniques go, it might seem like one of the more ambitious, especially if you don’t feel you get much bat action in your backyard. But it’s a genuinely effective treatment, and a little bit goes a long way. So if you’re not sure you can attract any helpful bats in the next few weeks, a quicker way to kickstart the soil amendment process is to buy some highly rated Dr. Earth Pure & Natural Bat Guano from Amazon. Some gardeners also soak guano in water overnight (1tsp of guano to 1gl of water) and then pour it over the soil for an unusually restorative tea.
5. Chicken Manure
Well, now that I’ve done the dirty and opened the floodgates on animal poop (and please forgive that mental image if you can!) I may as well share my favorite way to supercharge the soil in autumn: chicken manure. Adding aged manure to beds is an excellent soil amendment in the fall. The relative warmth of the soil gives animal-based top-ups the home field advantage, accelerating the process of accessing natural goodness like nitrogen, which in turn assists in improving soil structure and aeration levels. And on top of boosting airflow and drainage, there is an extra benefit to adding chicken manure in the fall – it helps to protect the surface of the soil, protecting it from rain and so preventing those important nutrients from being leached away.
There are a couple of ways of getting this perky nutrient source away from your chicken pals and into the ground. You can cultivate your own chicken manure – which is an idea for many growers as chicken gardening becomes more of an attractive sustainable option. However, creating your own chicken poop soil amendment isn’t simply a matter of enticing Henrietta Hen to squat over your flower beds (perish the thought). You can’t just add the poop fresh into the ground as that would be a big mistake – it’s so loaded with nutrients that it can actually burn plant roots in its raw form. As with other manures, chicken manure needs time to be aged before it can be added, either by being composted or cured. It also needs to be heated before use to eradicate the risk of salmonella and the like.
So your second option is to add chicken manure in granular form, making it easy to scatter across the soil surface as a topdressing. Try the highly rated True Organic Chicken Manure from Amazon, which can be added as a topdressing or worked into the soil for enhanced moisture retention.
6. Good Old Mulch
The beauty of mulch as a soil amendment is multifaceted and far-reaching. It helps to regulate soil temperatures, protects the earth from weather extremes, and regulates moisture levels. As long as you have removed weeds from a particular part of your garden before you add this soil amendment, your mulch of choice does a top job of suppressing future weed growth. And while it might be tempting to think of mulch as something that sits on top of the surface of the soil, several organic options break down and release nutrients into the earth (depending on the type of mulch you choose), as well as dynamically impacting structure. There are plenty of excellent natural mulching options which can be applied in the fall to give a measure of protection and sustenance as the seasons shift.
Give a little thought to which type of mulch is easiest to source, and how to apply it, to avoid common mulching mistakes that can adversely affect soil condition. Depending on where you live, your soil type, and plants you already have in your garden, you could easily create a very effective mulch to set your soil up nicely for spring. Gardeners with lawns can put those end-of-summer grass clippings to great use as a natural mulch, particularly on flower beds and veg patches. Pine needles are also in ready supply in many gardens, and break down amazingly fast, working well around shrubs. Straw is a great mulching option for potato growers, and bark is great for ornamental borders. If you don't have access to your own, you can buy Back To The Roots Organic Bark Bagged Mulch from Walmart.
If you use a shredder or chipper like the Yeryork Wood Chipper, Shredder and Mulcher from Amazon, you can quickly transform late summer shrub and perennial prunings into a mulching material that can be layered gently in various spots around the garden. Not forgetting another natural mulch source available at this time of year: leaves! Again, shredding leaves means they will layer better on the surface of the soil, benefiting airflow and the quicker release of vital nutrients as they break down into the soil.
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