Compost Critters

Phillip Peters
Adams County Master Gardener

Hi! You know me. Or, you should. Iím your compost heap. Iím the source of all that Ďblack goldí gardeners are always talking about. I sit out here behind the garden, day in, day out just hoping you will bring me more digestible goodies that I can make over into a rich delectable additive to put on your garden or lawn.

You may think Iíve got it easy Ė just sitting out here, basking in the sun. You may even think youíre the one doing all the work. After all, you do haul all those nice treats out to me. Donít think I donít appreciate those vegetable scraps, rotten left over salad bits and juicy green grass clippings. I really thank you and do a good job on those garden cuttings and plant prunings. And I love the way you mulch them up for me and mix them with straw or shredded newspaper and a bit of composted manure. And, of course, I really love it when you give me those periodic massages by turning me over every so often. You sprinkle on a little water to keep me from drying out, and Iím your friend for life. So, I can see how you think Iím just one pampered pile of mulch, relaxing out here, soaking up the rays while I enjoy the fruits of your labor.

But hey, while youíre over there weeding that plump little turnip on a hot summer day, or sitting indoors by that warm fireplace on a cold snowy evening, Iím hard at work out here. Compost doesnít just happen, you know! You may add all the ingredients, but Iím the one who works the magic. And, believe me, itís a full time job, 24/7 as they say. Oh, I may look calm and composed (get it?) on the outside, but inside Iím a seething cauldron of activity. Let me explain.

The real action begins when youíve finished putting me together. Itís then that all the bacteria and fungi come together for a feast. First, while Iím still cool come a group of bacteria called psychrophiles. These critters love it when my temperature is low Ė between 55į and 70į F. Some can live and munch on carbon products (the brown material) down to freezing before becoming dormant. These guys are opportunists. As they eat whatever carbon they find, they produce heat. But the critters also need oxygen and nitrogen to live. Thatís why you need to aerate me with a little stack in the middle or use an open sided bin so the air can get in to me. The green goodies and the manure give the nitrogen some fungi and bacteria love to eat. Now I start to warm up.

At about 70įF a new class of critters takes over the process. They really like temperatures between 70į and 90įF. Now the real banquet begins. They eat so much so fast that I really start cooking. This group is called mesophiles. Theyíll eat anything. As they eat, they reproduce; the bacteria replicate, and the fungi produce little microscopic bulbs that hold spores. These bulbs erupt and spread the fungus throughout the heap. It travels in the moisture you sprinkle on me. It may not be a pleasant thought, but this digestion, is what keeps me alive and going.

The mesophiles turn me on. All that tough cellulose and woody lignin in the plant waste is now being burned. At 100į the mesophiles go dormant; some species die. But now the true heat lovers take over. These are called thermophiles (thermo=heat, phil=love). Temperatures from 90į to 200įF are nothing for this crew. Stick your hand down under my surface when theyíre active, and youíll get burned. Hey, some of these fungi are the same guys that thrive in those hot springs and geysers. Theyíve got intimidating names like Chaetomium thermophile and Humicola insolens. But theyíre nice guys. They finish off those tough cell walls and woody materials and break down the proteins and complex by-products left by their predecessors. As my temperature gets to about 150į, those pesky weed seeds and nasty fungal spores you threw on me die. They wonít be alive to pop up in your garden next year. Hey! Treat me right, and Iíll look out for you!

When all the food is gone, the thermophiles start to die off. I start to cool down. The mesophiles wake up and feast on the leftovers. As they finish up the goodies, I really cool down. Now the big guys come out. Youíve seen them, the earthworms and millipedes. Maybe youíve even seen a large class of fungus working near my surface. Pull back my top covering and thereís a lot of threadlike, fibrous growth. These are actinomicetes (sounds like: act-in-o-MY-seats). Theyíre what give me that rich earthy smell that you like. They also help by producing enzymes that break down any woody cellular material that remains.

As you can see, Iím like a busy construction foreman. Think youíve got troubles? There are several billion critters in every gram of me!! I have to organize and coordinate this entire workforce to make you a happy gardener. And Iíve got to keep them happy so they donít go on strike and quit working.

But, I wonít let you down. When you see steam coming off me, you know Iím burning for you, baby!

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