Why is there dirt?

Question

I can understand rock having been molten or pressurized, and sand being broken rock, and clay being rock too finely broken, but why is there good dirt for plants to grow in? What makes dirt good? What makes it be not compacted and not dusty?

Answer 1

degredation of organic matter. Think of a compost pile. The vegetation, leaves, grasses degrade and make a wonderful medium that can sustain life. Here is a good excerpt...

This may seem a very BORING subject, but how you deal with your soil is the key to success or failure in all you do in your garden. Taking a few minutes now to learn how to build the kind of soil that will grow strong, vibrantly healthy plants, will save you a lot of frustration as well as time and money in the future. So I hope you will be motivated to take the time and effort needed to prepare your soil well. This bit is by far the toughest part of gardening and if you can't handle it yourself beg, borrow or hire someone who can! I can't stress this step enough. You may have the most wonderfully thought-out plan, and the highest quality plant material available, but if you plant in poor, under-nourished soil you are throwing your time and money away! The good news is, if you do the hard work right the first time you will only have to do it ONCE for the majority of your garden.

Healthy dirt is full of creepy-crawly things, from microscopic organisms and earthworms, to bugs and beetles. If you dig a hole and what you get is hard and compacted or looks a bit like beach sand, your dirt needs help. What it needs is ORGANIC MATTER - compost and aged manure*, "green manure", shredded leaves and other sorts of fluffy material, as well as a good helping of natural fertilizers like rock dust and greensand. These will start biological activities going in your soil, turning the "stuff " you add into something plants can use. That organic matter will help create a soil texture that has air spaces and will hold moisture in a healthy way (not staying wet and soggy for days after a rain like heavy clay soil, or drying out in 15 minutes like a sandy soil can).

Growing "green manure" plants, like annual ryegrass, clover and buckwheat, and turning them into the soil is an inexpensive way to add organic matter to soil you haven't planted yet. Compost and well-aged manure can be spread around existing plantings and will be worked into the soil over time by all the critters that will have been encouraged to join the project.

http://www.dfsgardenclub.org/organics/dirt.htm

Answer 2

by dirt do you mean soil???

a tree makes its own soil during its life time with the leaves it discards
the soil increasing with the growth of the treee which drop more leaves as it gets bigger

micro biotic life makes soil by helping the decomposition of organic waste making it rotten so that the worms can eat it and they produce the best compost known on this planet

there are as many kinds of soil as there are different kinds of birds
soils vary from region to region or altitudes,or depth of the soil

in agriculture we are usually concerned with the first two layers
the topsoils depends on what has gone before was there a lot of organic matter or biomass to create compost or were there arid conditions that people have enriched with additives,including compost.
are we talking about original soil or agricultural lands

the variations are far to much to discuss even on the surface ,there is a book by Russel that is thicker than the bible that talks about general soils on this planet.
some with a lot of earth or compost others sandy or clay.
rich soils and poor.
silica,(sand,lime,carbon are the principal components with an infinate varaity of elements such as nitrogen,phosphates,calcium,ox... ,clay etc etc.

there have been studies as to how soil originated on volcanic islands that are born with out any soil at all ,just cooling lava rising from the sea .
and it was found that the start is a drifting coconut that take root amongst the rocks.
coconuts produce a lot of waste with the husks and the continually descarded palm leaves.
this decomposes and is the birth of the soil in these places .this is where the micro organisms come in

over hundreds of years .passing birds droppings impregnated with other tree and plant species plant different species which in turn produce organic waste.
again with the help of micro organisms

and so over a long period mixed with the droppings of millions of birds a rich soil is created on these isolated volcanic islands.

Land masses have been at it much longer and with much more varied vegetation
.

Answer 3

Well that's easy...Worms have to poop...