30. Mar, 2022

Growing in Compost 1

Compost Awareness Week  2022   May 1 -7th  

Schools  or  Allotment /Community Garden project

Comparing growth in different composts could provide a simple but photogenic project for children at school or on allotments. A group or class could use pots of different composts to grow plant purchased in strips from the greenhouse or from  the local garden centre. The compost could be commercially available comparing different brands, or peat and peat free or taken from home composting bins. 

At Stokes Wood Allotment we are using samples taken from dalek bins,  a Green Johanna, Hotbin, Pallet bins (one which has over-wintered), and an anaerobic heap. Cos Lettuce  are being used as the test plant as  they make good leaf growth and should photograph well.

If photos are sent to carryoncomposting@gmail.com  we will publish them on the website, or they can be posted directly to https://www.facebook.com/carryoncomposting

Planting in Compost

Home Compost is traditionally  applied to the soil as a mulch, in a layer an inch or two thick,  to provide  organic matter to improve the structure and properties.  A gap will be left round the plants so that the compost  does not make direct contact.

 Indeed,  if searching the internet under “growing in compost, it would appear that the  general consensus is that  compost should form  only a small proportion of the “soil” material and that it is not advisable to grow directly in compost.  Although the evidence of your own eyes, during the season after  composting plants such as tomatoes, pumpkins and squash,  may show   that at least some plants  survive and grow well in pure  compost heaps.  

Despite this, the  view remains  that compost  will “burn” plants heating  up as its  organic content  breaks down. This  tends to assume that immature compost is being used before the composting process has been completed rather than waiting  until it has  matured if it is to be used near growing plants.   Burning is also said to occur where manure-based compost has a  high phosphorus content or is used without  be left a season to mature.  As manure-based compost  will not be used by most home composters this should not be a problem and if manure is used at all,  it will only be in small amounts as an activator

Another reason given for not growing in compost is that has  inadequate water retention. This assumes the  grower does not  check the moisture  content of the growing medium and apply water if it is dry. Some also argue that the structure of the compost will not  support tall plants, which assumes tall plants are not staked and that in the garden roots will not grow through the compost layer into the soil. 

It is also said that the  pH  level might be unsuitable. This is easily checked  most vegetables favour a pH   between 6.0 and 7.0 or 7.5  and most finished home compost has a pH of 6-8 

The answer to the  question  might be provided by  no-dig gardeners who  plant into compost and can often show a higher yield than obtained by those who dig When starting a bed, a 15cm/6in compost layer will often be used  on top of layers of cardboard. The plants will initially grow in the compost eventually reaching into the soil which will provide support. Once no dig is established   vegetables beds, will benefit  should receive about  1in/3cm of compost each year.