1. My compost is wet, soggy or slimy
Nothing is worse than cold, slimy compost! How does it get this way? Three factors are usually to blame: poor aeration, too much moisture, or not enough nitrogen-rich material in the pile.
A compost pile overburdened with materials that mat down when wet—grass clippings, spoiled hay, heaps of unshredded tree leaves—can become so dense that the pile's center receives no air. If you leave such a suffocating heap uncovered during a prolonged rainy spell (and don't turn it to introduce some air into the center), you'll end up with a cold, soggy lump that just sits there.
Aerobic bacteria—the tiny microorganisms that make compost cook—cannot live in such an oxygen-poor environment. What you instead make welcome in such a pile are anaerobic bacteria, which don't require air to thrive. These microbes will eventually make compost, but they work much more slowly than aerobic bacteria and the compost will be slimy and soggy during the long (about 2 or 3 years) process.
This would be no big deal for a patient gardener, but an anaerobic compost pile makes a lovely home for sow bugs, pill bugs, and earwigs—all undesirables. And you can be sure that such a pile won't get hot enough to kill any weed seeds it contains, either.
Fortunately, soggy compost is fairly easy to fix. If relentlessly wet weather is part of the problem, place a loose-fitting lid or tarp over the pile. You'll also need to turn the pile over and fluff it up thoroughly. If you have some "hot," nitrogen-rich ingredients (like shellfish shells) and fibrous, nonmatting ingredients (like shredded corn cobs or sawdust), add them to help get things cooking. Your pile should heat up within a few days, after which you can keep it cooking by turning it every week or two.
2. My compost is dry and dusty
Chances are, you live in the West, meaning that you are probably a little dry and dusty, too! This is quite common from May to October in areas where summer rainfall is practically nonexistent. No matter what materials you pile up, the stack just doesn't get enough moisture to support the bacterial life necessary to fuel the composting process. Luckily, curing dry and dusty compost is as simple as turning on a spigot. That's right, water it!
Here's a rule of thumb you can rely on: Your compost ingredients should feel about as wet as a damp sponge when they're in the pile. Put an oscillating sprinkler on top of your dry compost pile and run it for an hour—this will moisten the materials better than running an open hose on top. After sprinkling, check the center of the pile to be sure it's moist—sometimes you'll need to turn the pile and water the layers as you go.
Turning and watering your dormant pile should bring it to life quickly. If it doesn't heat up, it might lack nitrogen-rich materials. If that's the case, tear the whole thing apart, add some manure or bloodmeal to get it going, and pile it up again.
And once the pile does start cooking, don't let it dry out again. As they multiply, those tiny microorganisms use up a lot of water. You may have to water your compost almost as often as you water your roses during a heat wave!
New for your e-reader or tablet: Compostology 1-2-3.