Compost Lessons

I knew from past experience that I had made a lot of compost that for some reason did not seem to nourish my plants, I was still having to feed the garden with liquid comfrey, fish, manure tea etc to keep the plants growing. I now know my compost heaps did not contain enough carbon, got too hot, went anaerobic, and because my mineral levels were way too low and out of balance, almost no available calcium, I was simply recycling deficiencies. More importantly after around 10 years of studying biological agriculture I have come to understand that when we liquid feed with minerals like nitrogen we are actually mainlining our plants in a way that grows low brix food and over time destroys the humus and the soil we depend on. It is not a regenerative or even sustainable option. I have come to understand that growing nutrient dense food, is the same process as growing humus growing soil and growing healthy people and animals. There is no short cut, we must follow the rules, or ‘laws of nature’ or principles of science. If we take short cuts we will inevitably be doing something that does not grow nutrient dense food (easy to test with a refractometer) and degenerates our soil. I can no longer support that, it is time to make big changes.


It all comes back to:

  • Aeration
  • Moisture
  • Humus/carbon
  • Minerals
  • Microbes …. In that order

We need all of those bits to have a functional rhizosphere and we can not grow nutrient dense plants or humans or soil without a living alive earth . For home gardeners I believe the best way to make that happen is through the compost heap. There are many other options but this is the way most of us will learn to do it.

This means we need to upgrade our composting skills. I’m doing that…. and the results are very encouraging , if not exciting! For the first time in my gardening career I’m actually beginning to grow plants from my compost, and not liquid fish and comfrey etc.

One of my main aims after having read and re-read the Ecology Actions booklet Grow BioIntensive Composting and Growing Compost Materials was to be very conscious I was keeping the temperature as low as possible, in order to hold all the carbon, nitrogen and microbes in the heap to return to the soil rather than having them lost to the atmosphere in the case of carbon and nitrogen. I also wanted to make sure I was doing things efficiently so that I was not wasting my time.  The booklet explains how easy it is to make poor quality compost. I wanted maximum return for my hard work and the cost of inputs

Compost Thermometers

Firstly I bought a compost thermometer. I’ve never had one of those before and I can now see that most of my answers have been found by looking at the thermometer. If the temperature is too high, I haven’t got it right. I was aiming for an absolute maximum temperature of 55°C, but preferably less than that, 50°C.

Strategies for making humus efficiently (notes from Ecology Action Booklet)

1) We will produce more cured compost per unit of material with which the pile is built when we follow 45:1 to 60:1 mature (brown) :immature (green) ratios, rather than 30:1.the usual recommended way to do it… 60:1 best

  • Pile may heat to 57oC in first two weeks but then goes from 49oC to ambient and cures slowly
  • More efficient decomposition, less oxidization up to 30% more cured compost than in 30:1pile
  • Also a wider range of microbial life present
  • 45:1       2-2.5parts mature; 1 part immature; 1/3 part soil
  • 60/1       2 ½ -3 parts mature;1/2 part immature; ¼ part soil

2) Use composting materials higher in lignon eg cardoon, sorghum, sunflower, corn, mature lupins because they are the most carbon efficient decomposers

  • When lignin decomposes it is transformed into complex structures that protect and store carbon, nitrogen and other structures that are then gradually released
  • Piles built with highly lignaceous materials will have greater amounts of slower releasing carbon and nitrogen in them

3) Compost made using 45:1 ratio achieves twice the vegetable production of 30:L1 and 60:1 twice as high again

Making Compost: Patterns

  1. size of heap… minimum size ensures you have volume to insulate the heap so that curing is possible.
  • minimum volume 1m x 1m x 1m
  • optimal 1.6 x 1.6 x 1.2 high
  • maximum 3m x 1.6 high and any length you like
  1. immature vegetation contains metabolic carbon
  2. mature vegetation structural carbon together these two kinds of carbon make 90%of the volume of the heap
  3. top soil is 10% of the volume of the heap.. using soil increases the effectiveness of the heap.. holds temperature down, helps prevent temperature spiking and release /oxidation of carbon/nitrogen and microbes to the atmosphere. Soil helps hold minerals in the humus produced.
  4. adding minerals to your compost is the cheapest and most efficient way to add them to your soil, the microbes will pre-digest the minerals which will make them more plant available. I add seaweed for a good range of minor elements, either garden lime or burnt bones and shells, or crushed bones and shells for calcium, biochar ( carbon/charcoal ) to increase the effectiveness of humus building in the soil building process, I add iodine as well, ½ cup of Stock Iodine from local farm shop in 10 litres of water throughout the heap and I also plan my garden so that the carbon crops I grow concentrate the minerals that my soil needs. Eg Lupins and oats accumulate calcium and phophorous, both minerals are low in most NZ soils. I also add EF:Nature’sGarden to each heap as a sure way of remineralising the humus and the soil so that the health and nutrient density rises each year.


Making Compost: Process

  1. use fork to loosen soil.. facilitates proper drainage/moisture levels/aeration
  2. 6-10cm layer of rough vegetative material eg corn stalks, sunflower stalks, parts from last heap that didn’t decompose like corn end stalks with roots on them
  3. 5cm layer of mature vegetation then moisten when you ring with two hands 1 drop of moisture comes out no more!
  4. 5cm layer of immature vegetation and moisten
  5. 1 cm layer of soil and minerals moisten
  6. continue until 1.2 m high
  7. watch moisture levels, moist as a wrung out sponge, a drop or two, too much moisture means less air flow and anaerobic.. not enough makes decomposition difficult
  8. cover compost in wet or hot weather
  9. measure/monitor temp, moisture levels, aeration, colour and smell watch heap go through two stages.. heating then cooling and curing,

The Right Moment

Another part of the art of making and using compost is to dismantle the heap and get it onto the garden at exactly the right moment. If you leave your heap past the second stage, when it becomes dark and smells like forest floor, all the mineral transactions will have taken place and you will just be adding more soil to the garden, rather than all the energy potential from the decomposition process. I’m working with that… I can see we need to be in very close touch with all heaps and be checking out what they smell and feel and look like every week. This really is an art!

This is how to tell when the compost is ready

  • When most of original material and ingredients unrecognizable
  • Smell fresh and woodsy like spring water
  • Material dark brown or black soft and crumbly

Our heaps are looking very good, we kept the temperatures slightly over 50o C maximum and going through the stages compost goes through. We will continue monitoring our heaps and keep you in touch.. we believe we will end up with 30% of the original material as high quality humus capable of growing heavy crops of high quality vegetables….as our trials and work so far is indicating.