Advice on making compost


I wish to encourage you to discover the fun and interest of making compost!

Compost varies enormously, and homemade compost is the most variable and interesting, thanks to the seasonally-changing ingredients. Making compost is a fascinating hobby and if you never tried it yet, do have a go. You are turning wastes into something valuable.

Facebook 13.8.18 Richard Loader on UK Here We Grow

Since visiting Charles Dowding garden and seeing his composting system we have started to see our compost heaps very differently. Previously weeding, trimming, mowing seemed like chores but now these activities have become harvests of food for what we now call ‘The beast’. We gather the ‘browns and greens’ and blend them so as to satisfy the appetite of the beast and enjoy monitoring the process of decay and heating with a long probe thermometer. It’s like having a new pet to care for.

A compost heap transforms even persistent perennial weed roots into food for soil organisms and plants. Don’t believe everything you may read about what you “Can and cannot” compost – see this from Stringfellow in forum topic, horsetail 16/06/18:

I had a lawn of Horsetail covering my plot. Being a total beginner back then, and paranoid about horsetail growing through concrete bunkers etc. we mowed the top growth and skipped the lot. Now wish I’d composted it all. Just keep an eye on the heap, you’ll get little if any regrowth – I’ve found they quickly wither and die. It all ends up back on your plot to help grow veg.

Why compost, not just a mulch of undecomposed matter?

Compost is organic matter that has decomposed, from leaves and manure to weeds, wood and paper. Compost feeds soil in a slow and steady manner, allowing soil to feed plants. In gardens, a compost heap speeds up nature’s process of decomposition, resulting in less slugs than from mulches of undecomposed matter, and stronger plants.

  • Organic matter enables soil to aggregate into crumbs, for stability and aeration, and is food for soil’s billions of mostly unseen inhabitants. Organic matter is carbon, and more in the soil means less in the atmosphere.

Fresh manure or dung is organic matter, so far so good, but compared to compost it contains less living organisms such as fungi, and its nutrients are more water soluble. Hence the worries over nitrate leaching from slurry, which confusingly have been transferred to include compost.

I write ‘confusingly’ because in compost, nutrients are mostly insoluble in water, so they do not leach in rainfall. And compost is about way more than nitrates/fertiliser/plant feeding.

Compost quality

Ripeness means that a heap’s warmth has mostly gone, because the processing is finished. Often brandling worms arrive at this point, and heaps become wormeries of reduced quantity, increased quality. It can take up to six months before worms appear in my heaps at Homeacres, which are too warm for worms until that point, except in winter.

Contrast this with municipal compost which looks fine and “finished” after just a few weeks, from being shredded and then turned, regularly. However its blackness is from carbonisation caused by high temperatures, up to 80C, because huge numbers of thermophilic bacteria are encouraged by the regular turning and introduction of air.

I take deliveries of such compost and measure temperatures of 60C, even though the appearance is ‘like compost’, black and crumbly. I have tried spreading this compost and then planting through it, with poor results compared to when I spread it after six further months of fermentation.

You can plant/sow into green waste compost once it has cooled down and ripened. Check its heat when delivered, perhaps your supplier has kept it for enough time that it’s ready to use.

In 2016 I invested in a shed for my composting area, to keep the rain off. In the UK, water is often changing aerobic composting to anaerobic, by excluding air. Anaerobic compost is black rather than dark brown, more smelly and less crumbly. Hence a polythene sheet over heaps is worthwhile to keep rain off – to keep air in, not for preventing leaching!

(some of the below are extracts from my article in Which? Gardening July 2017)

Ingredients, green, brown and moisture

  • Green ingredients are soft, leafy, high in nitrogen, usually moist, and are low in fibre. Kitchen peelings and food wastes are mostly green. They lead to high temperatures.
  • Brown ingredients are fibrous, drier and more woody than leafy.
  • Some materials are both green and brown.
  • Some green ingredients such as coffee grounds and horse poo (both 3% nitrogen) look brown.

Why differentiate? When you achieve the desired balance of about 50:50, or a perhaps a little more green than brown, this contributes to a correct level of moisture, warmth and structure/aeration.

In the British climate, air is often damp and so are the materials we add to the compost heap. As they decompose, their moisture becomes free to seep into the heap and if it cannot either drain out, or be absorbed by drier materials, the compost becomes soggy and airless, or anaerobic. This slows or halts the process of breakdown: adding paper, soil and other brown ingredients is a remedy.

In contrast during the dry summer of 2018, I actually watered the compost heaps. Especially when we were turning them and many dry pockets became visible. Moisture levels are hard to assess.

Photos below are Homeacres October 2018, the year’s fifth heap 1.5m/5ft2

Good to compost

  • Weeds (green) include some soil (brown) on their roots, so you can make fine compost from them alone. You can compost perennial weeds too: I add roots and leaves of bindweed, docks, nettles, buttercups, dandelions and couch grass. They break down even in winter’s cooler heaps, and regrow only if left exposed to light. You can save much time by not separating out perennial weeds.
  • Fresh leaves are green and older leaves become more brown, so autumn tree leaves are mostly brown.
  • Rhubarb leaves and citrus peel are good to compost, I know from experience. Eggshells bring structure to a heap but decompose slowly, often ending un mulches on top.
  • Diseased leaves are good to compost, such as mildewed courgette and lettuce leaves, blighted potato and tomato leaves and also tubers/fruits with late blight. Blight spores for example need living plant tissue to survive in, hence they die in a compost heap, and likewise in soil. I spread compost which was made with blighted leaves, around tomatoes in the polytunnel, with no ensuing problems. Likewise blight spores do not survive in soil and there is no need to empty greenhouses of their soil.
  • Most shredded materials are woody (brown), and their speed of composting depends on size, and whether crushed or simply cut: crushed is best. I keep a pile of shredded branches near to the summer’s compost heaps, for adding to any large additions of grass mowings and fresh leaves.
  • Other brown materials are paper, best crumpled, cardboard which you can add in large pieces, wood ash (in winter my heaps are up to 10% wood ash), soil, and straw, which gives good structure and aeration.
  • Fresh manure from any animals is green and is excellent for speeding decomposition. Should you have large animals such as a cow or horse, their manure and bedding will ‘take over’ the compost heap, volume wise, meaning your compost heap has become more of a manure heap. Old manure is compost, just of a different quality.
  • Beware adding too much wood-flake bedding, often kiln dried and very slow to decompose. Not the end of the world, but your finished compost risks looking woody!
Compost thermometer

12 inch thermometer shows good breakdown is happening

Choice of bin: solid or open?

A bin with plastic or wooden sides keeps materials together, increases warmth and moisture, plus you can keep rain out if there is a lid or cover. It’s said that wooden bins need slatted sides to allow entry of air but I find this makes little difference: my heaps with plywood sides make great compost: they conserve both heat and moisture. I screw them onto corner posts, then it’s simple to unscrew them when turning and emptying heaps.

Plastic bins from the council are smaller and this restricts the heat they can maintain. My trial with a Rotol “dalek” bin saw temperatures rarely exceed 45C, and many weed seeds survived the process. Nonetheless it was good compost, and the sides are easy to lift off when you want it.

Base

Soil is best, for drainage, and for organisms to enter from below as heat subsides, or before it happens.

Building a heap

Add your garden waste as it happens, in level layers rather than a mound in the middle, to have uniform spreads of different materials as you add them. Sometimes you need “balancing materials” in terms of green and brown.

In much of the growing season there is a surplus of green, so keep a pile or some sacks of paper, autumn leaves, cardboard and twiggy materials, especially when adding grass mowings. In winter there is more brown, and some fresh manure or coffee grounds make for a good balance.

When to stop adding more material

  • Small gardens generate less material and may struggle to fill a bin, even over a whole year: use the smallest bin you can find because a fuller, small bin makes better compost than a half empty, larger one. After perhaps a year of filling, lift off the bin to a spot adjacent and fork the undecomposed, top part into it, then use the compost in the bottom part.
  • In large gardens, heaps may rise to four or five feet high within a month. Continue filling even after this for another 2-4 weeks as the heap will keep sinking, then cover with straw/carpet/polythene, preferably polythene to keep rain out, while you make a new heap. For best results, turn the finished heap after 1-3 months and leave another 2-4 months.

Turning compost: is it necessary?

Turning is worthwhile for larger scale compost-makers with several heaps, to mix and aerate. You need an empty space or bin next to the heap you are turning, and results will repay the time taken. Use a manure fork with long prongs, be sure to shake out any dense lumps: turning involves mixing, shaking and also allows you to check a compost’s quality. If you discover many dry lumps, add a little water, or conversely add some dry paper if it’s soggy.

For a small heap that perhaps barely fills up in a whole year, turning is not worthwhile.

The law of diminishing returns applies to compost turning. I never do a second turn as gains are much more marginal, compared to one turn.

Finished compost

Within a year you should find a crumbly texture of variable quality. If there are large lumps they need breaking up with a fork while loading your wheelbarrow. A dark brown colour is better than black, which would suggest some lack of air and too much wetness.

Sieving compost before use is not worth the effort and time needed. Simply pull out larger pieces of undecomposed materials, including roots of perennial weeds which are white and noticeable. There is nothing to fear from such roots because even if you missed them while spreading, you have another chance later when you see them start to regrow. Such visibility and easy removal are advantages of no dig with compost on the surface, instead of incorporated.

  • A quality of mature/ripe compost is that carbpn/organic matters has been transformed into humus, now known as glomalin. 

Glomalin

This was discovered only in 1996, by a scientist Sara F. Wright while working for the USA Agriculture Research Service. She discovered how to extract this sticky material which binds soil particles together, giving structure and tilth. It accounts for perhaps a quarter or more of soil carbon and exists for decades in undug/untilled soil, unlike most of soil’s short lived, non-mineral constituents.

It transpires that glomalin is almost certainly produced by mycorrhizal fungi, as Sara Wright describes:

“We’ve seen glomalin on the outside of the hyphae, and we believe this is how the hyphae seal themselves so they can carry water and nutrients. It may also be what gives them the rigidity they need to span the air spaces between soil particles”.

During plant growth, as roots extend further into soil, fungi close to the original roots die off at the same time as new fungi colonise and work with the developing root extensions. The decaying fungi shed their glomalin, and it remains in soil as a glue-like sheath around nearby particles.

This raises the intriguing point that plant growth helps build soil organic matter, as long as soil remains undisturbed.

“In a 4-year study at the Henry A. Wallace Beltsville (Maryland) Agricultural Research Center, Wright found that glomalin levels rose each year after no-till was started. No-till refers to a modern conservation practice that uses equipment to plant seeds with no prior plowing*. This practice was developed to protect soil from erosion by keeping fields covered with crop residue.”

“Glomalin went from 1.3 milligrams per gram of soil (mg/g) after the first year to 1.7 mg/g after the third. A nearby field that was plowed and planted each year had only 0.7 mg/g. In comparison, the soil under a 15-year-old buffer strip of grass had 2.7 mg/g.”

It’s reckoned that brassicas and beets* do not increase glomalin levels, since they do not work with fungal threads in order to grow. But most of our food crops, including cereals, do cooperate with fungi and scientists are now looking at fungal encouragement as a way to reduce dependence on phosphate fertilisers.

*Charles says, I doubt this. On my dig/no dig comparisons, I observe how the no dig brassicas and beetroot consistently outperform the same plantings in dug soil. I remember how in the early eighties I would read that mycorrhizal fungi were used by trees rather than vegetables. The ‘scientific’ view keeps changing because it’s a ‘snapshot’ of current understandings.

Compost and fungi

The new knowledge about glomalin ties in with older work by Albert Howard ninety years ago, on the value of compost. He taught farmers his recipes developed at Indore Research Station in India, and then he discovered how small applications of compost could transform the soil of tired tea plantations, enabling plants to rediscover their vigour. Howard had trained as a chemist and initially thought of compost in terms of chemical foods such as NPK, that it was recycling nutrients.

Then the results from using it, coupled with his knowledge that nutrient levels had barely increased because he was adding so few, helped him to see compost as a broad game changer. That was when he acknowledged the role of soil fungi, and the ability of compost to help fungi multiply.

At this time, in the 1930s, mycorrhizal fungi were being noticed and appreciated by scientists such as Dr Rayner who worked for the Forestry Commission, on Wareham Heath in Dorset.

Which brings us to the value of transforming manure and other wastes, into compost. I notice at Homeacres how crops grow better where the compost applied is fully ripe. It is dark, crumbly and the smell is sweet, not the ammonia or sulphur smells of manure stacked in an airless state.

Then to use your precious compost most effectively, the best method is surface mulching. Soil organisms are waiting, even in mild, winter weather, to incorporate surface organic matter: when you give them high quality compost, the results are wonderful.