I have been talking and emailing with Denise about soil building and she had some excellent advice I want to share with you. It was one of those AH HA! moments. Actually there were several AH HA!! moments because it explained things I was subliminally aware of not knowing (grin).
It has never been really clear in my head at what depth I should add the various soil amendments nor how to calculate how much to add back to the bed after I took out my tomato dirt.
What is tomato dirt?
That is the soil that was UNDER your tomato plants during the spring/summer gardening season. In a small 4' x 8' bed it is very difficult to rotate your vegetables very effectively to lower your disease pressure. To increase the chance of successfully growing tomatoes in the same bed the next year, we highly recommend you remove the tomato dirt and then plant the tomatoes at the opposite end of the bed. EVERY YEAR.
In the fall you are replacing the volume of the tomato dirt that was removed as well as replenishing soil nutrients. In the spring you are adding in amendments to replace the nutrients your plants used during the fall, winter and early spring. In other words, the amount you add in the spring is less than in the fall - usually.
What is tomato dirt?
That is the soil that was UNDER your tomato plants during the spring/summer gardening season. In a small 4' x 8' bed it is very difficult to rotate your vegetables very effectively to lower your disease pressure. To increase the chance of successfully growing tomatoes in the same bed the next year, we highly recommend you remove the tomato dirt and then plant the tomatoes at the opposite end of the bed. EVERY YEAR.
In the fall you are replacing the volume of the tomato dirt that was removed as well as replenishing soil nutrients. In the spring you are adding in amendments to replace the nutrients your plants used during the fall, winter and early spring. In other words, the amount you add in the spring is less than in the fall - usually.
What level your soil amendments should be incorporated:
Our beds are 12 inches deep. You need a base level of 8 inches of soil before you start incorporating any amendments. If you are starting with one of the beds that has been half emptied out (see picture to the side), fill it with the bagged topsoil until there are only 4 inches remaining (after grub removal and sifting - see bottom of this post for link and why you want to do this). I would mix the bagged topsoil with the soil from the original bed so it is blended well before mixing in any amendments.
You are making a soil cake here and want all your ingredients well blended!
For the healthiest production from soil that provides nutrients on a constant and balanced level, it is important to consider a few different concepts when adding amendments and at what depth to add them.
1) Consider the root structures (the main and feeder roots) of what you will grow to make sure food will be readily available at all levels. For example - if you were growing radishes with short roots. If all your soil amendments were at a depth of 8 inches and below, the plant would be totally dependent on your fertilization practices above ground to thrive or the theory that your soil is already healthy and productive.
2) Consider your additions. For example, if you are adding items like leaves, coffee grounds and egg shells, they would be considered unfinished compost items. They need to be placed lower in the soil, closer to the reach of the earthworms. This will speed their decomposition into available nutrients deep within the soil so when the plant roots get there the food is readily available.
3) If soil life is already healthy, meaning full of life and visible activity (worms are excellent indicators), turning amendments into the top layers enhances the activity and appetite of earthworms, fungi, and bacteria. They will all work in harmony to take matter deep within the soil wherever it needs to go. Nutrients will then be readily available at all levels for healthy root development and balanced plant nutrition.
Gardeners Math, Part 1
How to calculate how much to add to build up your bed
Our gardening beds are 4' x 8' = 32 square feet.
Our gardening beds are 4' x 8' = 32 square feet.
To replace a third of the bed - you need 10.67 cubic feet of amendments
To replace a quarter of the bed - you need 8 cubic feet of amendments
Jungle Grow - 2 cubic feet
Mushroom Compost - 1.2 cubic feet
Black Kow Cow Manure - 1.2 cubic feet
Worm castings (entire bag from Pike's) - 1 cubic foot
Bag of Top Soil - 1 cubic feet
If you are building a bed from scratch you would need 21 bags to create your 8 inch base layer.
Vermiculite really doesn't take up that much space as it is more of a fine powder that is incorporated through out the bed when you mix it in. It is wonderful at absorbing and then releasing moisture and nutrients back as needed.
Chopped up leaves fluff the area up but don't keep much bulk in the bed after a couple of weeks. It just provides lots of good organic matter while decomposing and feeding the worms.
Coffee grounds and egg shells also don't provide much bulk but are very good additives because the worms utilize them. Whatever makes the worms happy, makes the plants happy.
If your soil has been depleted by heavy feeders you need to ramp up your additives to support growing tomatoes in the spring. And also so your fall and winter vegetables will do well. If your bed doesn't have many worms definitely add in the things that will make them happy because the more worms you have, the better your plants will do.
Compost Tea and Coffee grounds will help activate microbes and get your worms going in your bed before the cold weather arrives. This helps to build healthy soil which leads to healthy plants. Compost Tea and Coffee grounds are also known to repel some insects and grubs are listed as one of them in the book, Teaming with Microbes, by Jeff Lowenfels & Wayne Lewis.
Approximate Cost of Amendments
Compost Tea and Coffee grounds will help activate microbes and get your worms going in your bed before the cold weather arrives. This helps to build healthy soil which leads to healthy plants. Compost Tea and Coffee grounds are also known to repel some insects and grubs are listed as one of them in the book, Teaming with Microbes, by Jeff Lowenfels & Wayne Lewis.
Approximate Cost of Amendments
Jungle Grow - $6.98
Black Kow Cow Manure - $4.98
Mushroom Compost - $3.96
Worm Castings (20 lb bag) - $20.99
Worm Castings (20 lb bag) - $20.99
Top Soil -$1.29
Grub Removal:
We highly recommend you work on removing the grubs before filling or refilling your bed with dirt. It makes a world of difference. There is a reservoir of grubs in the first 2 to 3 inches of the red clay that the beds are sitting on. They WILL work their way up into the bed.
Also, if your bed has never been sifted and you plan on growing carrots, now is the time to do it when you have LESS dirt in the bed! If you just got a bed and you don't know if your bed has been sifted, just ask us. There is not a need for sifting amendments. However, if you notice any rocks or large particles from their processing, you will want to pick those out.
Here is link to a previous post on how to sift, what to look for and what equipment to use
http://greenmeadowscommunitygarden.blogspot.com/2014/02/what-is-sifting-soil.html
When I dug down through my bed and into the red clay area in Fall 2012, I found 110 grubs. I did it again Spring 2013 and only found 30 grubs. Each time I find fewer grubs moving up through my soil because I've cleared out my reservoir of resident grubs. Unfortunately, you will always have some grubs because you miss a couple and because new ones are "deposited". Denise's soil continues to remain grub free, with never more than a couple, through what we expect is due the use of compost tea on a regular basis.
Good luck building your soil for the fall/winter growing season!
Good luck building your soil for the fall/winter growing season!
Vicki & Denise
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