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Wednesday, September 9, 2015

Vegetable Garden Soil - From Scratch!


Having moved in to my home only last summer, I thought that it was a good idea to do one or two garden beds at a time.  If I tried to do them all at once I would be biting off much more than I can chew!

This summer, I completed the herb garden and the small mailbox garden.

Next spring (2016), I plan to plant the vegetable garden!

It is true that a good garden begins with good soil.  Unfortunately, when I did my soil test on the bed that I planned to use, I discovered that the soil was very poor in nutrients and had a high (alkaline) pH of 7.8!  Something had to be done to rectify this before I can plant anything!

On top of that, there were 4 burning bushes in the bed blocking the western sun and spreading some gnarly roots throughout the bed.  To complicate things further, there are 2 wires running through the bed.  One to the pump for the sprinkler system, and one for the dog's electric fence.  Clearly the area would need some work before I could plant anything!


 First, I cut back the four, 8-foot-tall burning bushes and dug out the stumps.  This took the better part of a day, but was well worth it. The bed went from being part sun/part shade to nearly full sun.  There is some shade over the bed for part of the day due to the oak tree 50 feet away in the neighbor's yard, but the effect of this is minimal compared to the shade cast by the four large bushes that were directly in the garden bed.

My sandy, nutrient poor soil.
These bushes left behind an extensive root system.  Some of the roots were up to 1inch diameter. 
These were spread throughout the bed and made for some difficult digging later on.


 The next step was to improve the soil.  The native soil in the bed is sandy, alkaline and nutrient poor.  The advantage to this is that sandy soil drains well.  The problem is that nutrients wash out of the soil easily with the water.  For this reason, sandy soil is often low in the nutrients (nitrogen, phosphorus, and potassium - NPK) that plants need to grow well.

My goal was to improve the texture of the soil so that it holds a bit more moisture and nutrients, to increase the nutrient content of the soil, and to acidify the soil so that it has a pH in the range of 6.8 to 7.0.

In addition, I needed to pull the roots of the former burning bushes out of the soil, and to loosen the compacted soil.

Double-digging the trench - note the root and wire sticking out.
Originally, I considered tilling the soil to break up the root systems and to add my chosen soil amendments.  Tilling would have saved me a lot of time and effort because I could use a machine to do the hard work of digging. However, there were 3 problems with this: 1. There are two wires going through the bed for the pump and the electric dog fence.  If I used a tiller, these wires would be destroyed, and I could be injured.  2. I would have needed to rent the largest and most expensive tiller available from the big box store in order to cut through 1 inch roots. 3. Unless I tilled very carefully and lightly, there was danger that I could work the soil into a fine powder which would destroy the soil tilth and lead to worse compaction than I started with!

spreading soil amendments in the trench.
So, I decided to bite the bullet and double dig all 300 square feet of root-filled soil by hand. This process allowed me to add soil amendments, to loosen the soil and to rip out the old roots a little at a time.  Double digging involves making a trench in the soil, adding compost and soil additives to the bottom of the trench, then spreading the top soil and some compost back over the top of the trench. In my case, I chose to add a mixture of 3/4 composted horse manure, 1/8 sphagnum peat moss, and 1/8 recycled used coffee grounds. Once I covered the compost in he trench over with the top soil, I also spread a thin layer of soil acidifier, peat moss, coffee grounds, and compost to the surface of the soil and covered that with mulch. Double digging the entire bed, by myself, by hand (including hauling the manure from a pile to the back yard) took me approximately 15 hours of time, spread out over several weekends. (It also caused me to grow Pop-eye like muscles ;) and gave me a nasty, blistering sunburn!!)

Luckily, I should only have to double dig this garden ONCE.  Now that the soil has been loosened, and a base layer of organic matter has been added, I can maintain the soil more easily in the future simply by adding compost to the hole when I plant, and spread about an inch or so thick over the surface of the soil.  Also, now that all of the roots have been removed, digging holes for planting will be WAY easier! 


I spread my soil amendments about 2-3 inches thick along the bottom of the trench that I double-dug, and then mixed the topsoil back over and in with the amendments. The amendment mixture I used was made up of the following: 

1. Composted Horse Manure -  I do make my own compost, but did not have nearly enough to cover the 300 square foot area of my garden.   So I loaded up a truck with some lovely, FREE, composted manure from Brighton Rec Stables.  3/4 of my added soil amendment was made up of horse manure. Horse manure is high in organic matter and has NPK values of approximately 0.7-0.3-0.6.  (Please see this website for more information on the nutrient content of various manure types: Manure NPK.) As you can see, the nitrogen content is low enough that I do not need to worry about "burning" my plants.  Actually, unless you bury your plant with a ridiculous amount of fresh, wet manure, it is very difficulty to cause harm to most plants.

Cute compost makers!
2. Recycled Coffee Grounds - Starbucks, and other coffee vendors will give you their used coffee grounds for FREE if you ask for them at the front counter. 1/8 of my added soil amendment mix was made up of used coffee grounds. These grounds have an NPK value of 2.28-0.06-0.6 and a pH of 6.2. They are also high in copper, and earthworms love to munch on them! (For more information see test results at the Sunset website.)  There is a rumor going around that used coffee grounds are dangerously acidic.  This is not true.  Ideal soil pH is 6.8.  Used coffee grounds have a pH of 6.2 and are being mixed with your native soil.  Once mixed with the soil, the pH of the coffee grounds is negligible.  Unless you are planting in pure used coffee grounds, or soil that is mostly made up of coffee grounds, this should not be a problem. It is even less of a problem in my garden, with my super alkaline soil of pH 7.8.  My soil needs to be acidified!

3. Sphagnum Peat Moss - Peat moss contains little in the way of nutrients (NPK), but is great for adding organic material to the soil. 1/8 of my soil amendment mix was made up of peat moss. The peat moss helps to hold moisture and nutrients in the soil.  It also has a very acidic pH of 4.0 (way more acid than coffee grounds!).  This pH is low enough to actually lower the pH of the native soil and is often used to acidify the soil around azaleas and blueberries.  Because my soil was so alkaline (pH 7.8), I chose to add a small amount of this as a soil amendment along with my compost and coffee grounds. 

Raking the soil back into the trench after adding soil amendments.
4. Soil Acidifier - The soil acidifier that I used was 30% sulfur.  The package recommended using 12lbs per 100 square foot of garden space for every 1 point in pH reduction desired.  I only used about 6 lbs over the entire 300 square foot space.  The reason that I used less than was recommended was because I was already adding peat moss, coffee grounds and compost to the soil. The combination of these items, especially the peat moss, should lower the pH somewhat already.  I did not want to lower the pH too much. Therefore, I added much less acidifier than recommended.  In the spring, I will test the soil pH again and will add more acidifier if needed.  The reason that I am not testing the soil pH now is because I want to give the earthworms, insects, weather, water, and "Mother Nature" in general time to "mix" my soil additives in to the native soil of the garden.  By the time spring arrives, the peat moss and sulfur should be worked in to the soil enough to change the pH somewhat.  I can make adjustments from there.

5. Mulch -- I already had some wood-chip mulch on the garden bed, left over from the previous owner.  However, this mulch had partially decomposed and was not enough to cover the surface of the bed to a depth of 1-2 inches as I would prefer.  So, this fall, I will be dumping shredded leaves from the local oak trees onto the bed as a mulch.  This will help hold moisture in the soil and prevent weeds.  Leaves are also very high in nutrients and break down into "leaf mold" as they decompose.  In addition, earth worms, beneficial bacteria and beneficial fungi love to eat them!  They should greatly enhance the viability of the soil over all.

Note:  Everyone's soil is different! Please test your own soil and decide what you want to add to your particular soil.   If you have acidic soil, you may want to add lime to "sweeten"/add alkalinity to the soil.  If your soil is neutral or between 6.8-7.0, you don't need to adjust the pH and may only want to add compost.  If you have heavy clay soil, you may want to add a lot more compost than I did. (Never add sand to clay soil! Never add clay to sandy soil! This will turn your soil into CEMENT!! Do add compost instead!)  If you need advice about what to add to your soil, please get a soil test and/or contact your local extension office for advice! Click here for the link to MSU extension "Ask an Expert".  Click here to find out how to test your soil.


 Next spring, I will be planting vegetables in the garden.  Before I do this, I will be adding corn gluten meal (organic Nitrogen - N), bone meal (organic phosphorus - P), and potash (organic potassium - K) to the soil in the amounts recommended by the soil test that I had done by the MSU lab.
My home-made compost before and after.
I will also be adding 2lbs of azomite rock dust to the soil in order to boost some of the trace mineral elements in the soil.  Azomite only has an NPK of 0-0-0.2.  But it contains 67 other elements including  1.8% calcium, 0.5% magnesium, 0.1% chlorine, and 0.1% sodium. 

In addition, I will test my soil pH again with a home soil pH testing kit to see if I need to add more soil acidifier or not.

Finally, as I plant each vegetable, I will add some of my home-made compost to the hole and soil surface for an extra boost, as well as to help maintain the amount of organic matter in the soil.


To keep my soil healthy, I will continue to add compost and/or manure to the soil each time I plant.  I will put some compost in the hole, and will spread some over the surface.  I will also add a thin layer of coffee grounds each year, as well as the recommended amount of corn gluten meal to keep up the level of nitrogen.  Nitrogen needs to be added yearly in a controlled amount because it dissipates into the plants, and into the air over time.   I will continue to mulch with leaves in order to keep up the level of minerals in the soil.  I plan to test my soil pH yearly using a kit from the local big box store, and to get a soil lab test every 3-5 years, or if my plants show signs of problems.


Pimp My Soil!!
Pimp My Soil - Part Deux!   
Soil - Timing is Everything
MI Free Compost
Make Compost Tea
Red Worms & DIY Vermicomposting

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DIG!! DIG!! 


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