Some people expressed an interest in a thread about using topsoil as part of an organic soil mix so here we go.
First off - Here are what I see as the potential advantages and disadvantages of topsoil.
Advantages –
1. soil is what most plants have evolved to grow in. We refer to our medium as soil but mostly it has no ‘real soil’ content
2. Good micronutrient content. Soil is the ultimate in aged rock dust!
3. Potential to impart flavour – i know from my own experience that vegetables grown with soil in the potting mix have better flavour than those grown in only peat/compost.
4. Holds water well and no re-wetting problems
Disadvantages.
1. Heavy – may become compacted
2. Risk of introducing harmful pests/diseases. Jorge Cervantes recommends not to use soil dug up from the garden/field.(more about this later).
3. May hold too much water.
4. Quality will vary.
At present I use a good quality bagged topsoil as about 20-30% of my mix with great results. I have yet to do any side by side comparisons but I’m very happy with the taste, aroma, high and yield of my plants. (check my grow diary for pics. All of the plants shown were grown in a mix pretty much like this.)
3 parts peat
2 parts topsoil
3 parts perlite
1 part mushroom compost
1 part wormcasts
2 parts coco (optional - to keep open structure preferred by sativas)
dolomite lime 5g/litre
N guano - 5g/litre
P guano - 10g/litre (5g/litre for veg)
Rock phosphate 5g/l
rock potash 5g/l
seaweed meal 5g/l
Bagged soil
Topsoil from the garden centre is likely to have been sterilised/solarised so may be a safer bet than garden/field soil. Having said this I have seen some shite topsoil from a bag so I prefer to check the quality before I buy it. Look for a bag that has already split and get a handful. You are looking for a nice dark tilth with good crumb structure (not dusty). If you squeeze damp soil into a lump it should stick together and feel slightly spongy - and when the lump is pressed gently it should easily break back up into tilth again. It is also worth pointing out that even the same brand of topsoil (and compost for that matter) will vary from place to place as the source will vary. Always best to check.
Garden / field soil.
I would also like to take this further and try good quality garden soil. Again It helps to have experience of what good soil is. If you want to try this you should research solarisation (leaving to cook in the sun to kill pests/diseases) or some form a gentle sterilisation. I would also recommend sieving and keeping a look out for any larvae/cutworms that could give you real problems. Certain plants/weeds can tell you something about the native soil – nettles for instance are a good indicator of fertility.
I am planning to try some clay soil as well – clay can get very wet and soggy but a well cultivated clay soil is amongst the most complete in terms of fertility.- the small partical size in clay (whilst it has it's disadvantages) gives a huge surface area - some clay can have a surface area equivalent to the size of a football pitch in every gram! - this surface area has a major influence on the soil's ability to hold onto nutrients rather than them leach out. Moreover, clay particles are pretty unique to soil in being negatively charged - which makes the all important ion exchange much greater.
hopefully we can expand on this
V.
First off - Here are what I see as the potential advantages and disadvantages of topsoil.
Advantages –
1. soil is what most plants have evolved to grow in. We refer to our medium as soil but mostly it has no ‘real soil’ content
2. Good micronutrient content. Soil is the ultimate in aged rock dust!
3. Potential to impart flavour – i know from my own experience that vegetables grown with soil in the potting mix have better flavour than those grown in only peat/compost.
4. Holds water well and no re-wetting problems
Disadvantages.
1. Heavy – may become compacted
2. Risk of introducing harmful pests/diseases. Jorge Cervantes recommends not to use soil dug up from the garden/field.(more about this later).
3. May hold too much water.
4. Quality will vary.
At present I use a good quality bagged topsoil as about 20-30% of my mix with great results. I have yet to do any side by side comparisons but I’m very happy with the taste, aroma, high and yield of my plants. (check my grow diary for pics. All of the plants shown were grown in a mix pretty much like this.)
3 parts peat
2 parts topsoil
3 parts perlite
1 part mushroom compost
1 part wormcasts
2 parts coco (optional - to keep open structure preferred by sativas)
dolomite lime 5g/litre
N guano - 5g/litre
P guano - 10g/litre (5g/litre for veg)
Rock phosphate 5g/l
rock potash 5g/l
seaweed meal 5g/l
Bagged soil
Topsoil from the garden centre is likely to have been sterilised/solarised so may be a safer bet than garden/field soil. Having said this I have seen some shite topsoil from a bag so I prefer to check the quality before I buy it. Look for a bag that has already split and get a handful. You are looking for a nice dark tilth with good crumb structure (not dusty). If you squeeze damp soil into a lump it should stick together and feel slightly spongy - and when the lump is pressed gently it should easily break back up into tilth again. It is also worth pointing out that even the same brand of topsoil (and compost for that matter) will vary from place to place as the source will vary. Always best to check.
Garden / field soil.
I would also like to take this further and try good quality garden soil. Again It helps to have experience of what good soil is. If you want to try this you should research solarisation (leaving to cook in the sun to kill pests/diseases) or some form a gentle sterilisation. I would also recommend sieving and keeping a look out for any larvae/cutworms that could give you real problems. Certain plants/weeds can tell you something about the native soil – nettles for instance are a good indicator of fertility.
I am planning to try some clay soil as well – clay can get very wet and soggy but a well cultivated clay soil is amongst the most complete in terms of fertility.- the small partical size in clay (whilst it has it's disadvantages) gives a huge surface area - some clay can have a surface area equivalent to the size of a football pitch in every gram! - this surface area has a major influence on the soil's ability to hold onto nutrients rather than them leach out. Moreover, clay particles are pretty unique to soil in being negatively charged - which makes the all important ion exchange much greater.
hopefully we can expand on this
V.
