Buying soil for veggie beds

Grow healthy soil and you will have healthy vegetables is the motto of many food gardeners, so, when starting a new veggie bed, people want to buy the best soil they can get. Many food gardeners, however, have been disappointed with the quality of soil they bought. The aim of this blog post is to give people a few ways of checking the quality of soils before buying, so they can make the best possible start with their new veggie bed.

Well-made home-made compost is the best thing you can use to improve your garden. However, when it comes to adding a new veggie bed, there is often not enough compost on the compost heap to fill the entire bed, so that is when food gardeners buy soil from a nursery or specialised soil company.

The problem is that when we order a load of 'veggie mix' soil we often have no idea what the quality of the soil will be.

In a recent discussion about buying soil on our group's Food Gardeners Tasmania Facebook page people complained that the quality of soils varied a lot, that some sandy soils had no puff, that soils were far too alkaline, or that there were plastics in it or un-composted organic materials. One person complained that their new soil actually stunted the growth of plants.

This blog post is an attempt to give people a few tools to assess soils before buying them.

It is really important to buy the best soil you can get for the money that you are prepared to pay because, if there is a problem with the soil you buy, that problem will be yours to solve once the soil has been delivered to your garden!  

Commercial soil suppliers face a number of challenges in their aim to sell mixes that are consistent in quality. 

The quality of compost is very much influenced by what materials go into the composing process and it may not always be possible to get the same materials throughout the year. 

Also, the temperature at which compost is made will not always be the same. Making compost in winter may be at much lower temperatures than in the middle of summer. One summer a large compost heap at the Glenorchy tip even caught fire.

Composting at high temperatures can create significant amounts of ash. The result can be 'dead compost' with a pH significantly above 7. 

The result of these variables in the compost making process is that composts will not always be the same, even if the supplier does its very best to provide consistent quality.

Compost is often just one ingredient in the 'veggie mix' that is sold to the food gardener. Commercially produced veggie garden soil is a mix of sandy loam, compost, pine bark and often one or more manures such as pulverised cow or chicken manure. Prices of veggie mixes will vary depending on how much compost, what manures, and how much manure, are present in the mix.

Suggestions for assessing the quality of vegie garden soil

• Do not just order soil over the phone. Go and check it in person.

• Buy a pH meter and visit the yard of the company just before the day that you would like the soil delivered. Then order it if you like the soil that is there.

Interesting pH ( 6.0 )

• Ask the person at the counter which soil mix will be the best for your new veggie bed and what is in this mix. This might explain its price.

• Ask whether you can have a look at the soil. I found most sales people to be very helpful. They had no problem with me fossicking around the heap while they served other customers.

• Examine the heap that you were told is the best for your new veggie bed.

• Are there any inorganic contaminants visible? Dig a little hole. Any plastics, large or small?  A few small bits won't matter, but there is a limit. Your decision! Now at least you see what you buy before buying it.

The poo is a good sign, but there are also some bits of plastic

• Are there many un-composted organic bits? Un-composted manure is fine, but too much un-composted pine bark or large wood slivers is not. A lot of burnt woody bits would indicate that the compost was created at high temperatures resulting in soil with high pH devoid of micro-organisms.

• Dig a little hole. Is the soil at the bottom of this hole warm? I found this to be the case at one supplier. It meant that the composting process in the heap that was already being sold had not finished. You don't want to grow vegetables in that mix until you have composted it a bit further yourself.

• Is the soil at the bottom of this little hole moist or dry? Dry soils are not a good starting point for making good veggie garden soils.  

• Stick a ph meter as deep in the hole as you can. Wait a few minutes for the meter to adjust. The closer the pH is to 7.0 the better it will be for your veggies. Personally I would not buy soil with a pH below 6.0 or a pH above 7.5 for growing vegetables because it is too much work to correct the pH. 

• Without going into a lot of soil science: soil biology needs clay in small quantities. While you are waiting for the meter to do its work, dig another little hole.  Take some moist soil out of the bottom of this hole in your hand and squeeze, make it into a ball, then open your hand: does the ball fall apart, or does it continue to be a ball. Good veggie garden soils have some clay in them. If the ball falls apart when you open your hand this is not ideal veggie garden soil. 

• If you like the soil you have just assessed, order it there and then. If you wait a few days or weeks, the heap may be sold to other customers. The soil on the next heap may or may not be very similar to the soil in this heap, depending on the ingredients that were composted and the temperatures they were composted at.

These checks will go some way towards avoiding problem soils. In some cases the soil you get will be perfect. More often than not you will have to improve the soil you get to become healthy and productive over time.

I visited a few local suppliers of veggie garden soil

I brought my pH meter,  did my checks as described above, and found ......

Please note

In this blog post I do not recommend where to buy veggie garden soil because a recommendation would only be fair if I went around all suppliers around the state to test all soils. Also, I am not sure that the quality of soils is consistent enough over time to make such recommendation. Instead I suggest that you always do your own checks using the methods described above.

About the pH of these soils

To my surprise I did not find any soils with pH above 7. That may be because I did my testing in mid-spring. Alkalinity/Acidity of some commercially available soils may be well above 7 if you buy soil in summer or autumn because composting at these times would be hotter. For this reason it might be best to buy soil in spring! I hope to test commercially available soils again in late summer to find out whether soils offered for sale are consistent in terms of pH over time. 

If you would like to know more about pH, how to test it, and how to change it, see blog post Acid or Alkaline? on the Food Garden Group blog.

If you buy good soil .....

If you buy good soil you give yourself a good starting point for growing your first crop. If you then add compost and/or worm castings and/or complete organic fertiliser from time to time, you will gradually create a really healthy environment for micro-organisms and other soil creatures. You can find more info about soil, crop rotation and complete organic fertiliser in other posts on this blog.

Grow healthy soil and you will get healthy vegetables!

Max Bee