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Guy Barter answers your compost queries

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Guy Barter Guy Barter | 16:10 UK time, Thursday, 8 April 2010

This month, our gardening expert is the amazingly experienced Guy Barter, of the Royal Horticultural Society.  He's a bit of a whiz at giving advice on soil, compost and fertilisers, which is something we've had loads of questions about.  We've picked three of the best ones and put them to him - read his answers below.

If you've got a question about the Dig In veg for one of our experts, send it to us using the question form.

Carol asks: "Due to disability I use pots for all my veggies and flowers. Can I use last year's compost if I add fertilizer?"

Answer: Yes, as long as last year's plants were not diseased in the root department.  However I suggest adding at least some, say a third to a half by volume, fresh potting medium just in case the structure of the original potting medium has declined. 

Adding fertiliser is wise:  I generally add a teacup of growmore to every 15 litre bucket of potting medium.

Andy Withall asks: "What's the most efficient, from a cost versus benefit perspective, way of re-introducing nutrition to a small plot after a growing season. Manure? Compost? Purchased products? There is lots of choice but which is best?

Answer: Fertiliser is highly cost effective especially if bought from an allotment society or garden club. (These often band together to buy in bulk and get lower prices, Ed).    However good gardeners use plenty of organic matter too.  Home made compost is best, but few can make enough garden compost for themselves, so it's usually necessary to buy manure or other materials.  Bulk materials delivered by tipper lorry are much cheaper then bagged organic matter. 

I suggest manuring one third to half your plot each year with organic matter, and supplementing these (and of course treating unmanured areas) with fertilisers.  It does not matter much which fertiliser you use but granulated chemical fertilisers and chicken manure pellets are usually the most cost effective.  Naturally you will need much less, perhaps about half, the amount of fertiliser if you have added compost or manure to the soil. 

Thomas Gamby asks: "I have built some contained raised beds in my garden as the soil is very poor consisting of mainly stones and rubble. What should the beds be filled with? I have purchased numerous bags of compost from the garden centre, but last year they dried out really easily. Should I get some proper soil to add to the compost?

Answer: Potting media and growing bag media can be used to fill raised beds, but are rather costly and may lose their structure within a year or two.  Peat-based ones are also not good for the environment.  You could buy in topsoil, but good topsoil is hard to find and costly.  Often it is possible to add, say, 10% by volume of manure or other good organic matter to the poor soil that is present, remove debris and add fertiliser generously and get a usable soil that gets better with time. 

It is also best to allow your beds to rest on the original soil, poor though it is.  Fork over the underlying soil and add manure or other organic matter (1 bucketful every square metre) and then fill the bed bearing mind the need to have at least 25cm depth of good soil or growing medium. This should allow crops to get at least some water from below the bed and avoid the drought problems that you have found.



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