Get down and Dirty

Dirt fascinates me. For all of my gardening life, I've loved the look of it, the feel of it and the smell of it. But that's not fascination, that's enjoyment.
I became downright fascinated with dirt during the Master Gardener class when Gary Dauberman told us good dirt was 50 percent open space. How can this stuff we build on and stand on and dig holes in be 50 percent space, I thought to myself?

Dirt is like the amniotic fluid that surrounds a baby in the womb. It is the means by which the nourishment, water and air needed for growth are exchanged. The three components of soil - mineral matter (dirt and rock), organic matter and pore space - provide the structure that makes the exchange possible. Good dirt consists of 45 percent to 48 percent mineral matter, 2 percent to 5 percent organic matter and 50 percent pore space.

The open spaces make good dirt "fluffy," or friable, meaning the dirt crumbles easily: The open spaces, called pore spaces, provide channels for water and air to reach the roots of the plant

There are basically three different types of dirt - sand, silt and clay - whose primary difference is their size. Sand is the largest soil particle, clay is the smallest. Ideal soil is known as loam, which is 7 percent to 27 percent clay, 28 percent to 50 percent silt and less than 52 percent sand.

If a soil has too much sand, there is too much pore space and the water moves too quickly through it, there is also a lot of air in the soil and it heats up quickly.

If a soil has too much clay in it, there is not enough pore space and the water either has a hard time getting into the ground to reach the roots, or once it gets there, it stays there too long. That means there is not enough air reaching the roots. It's easy to compact clay soil - by too much tilling, or walking on it or digging it when it's wet, for example - thus removing even more pore space.

The organic matter mentioned earlier plays a key role in good dirt. Organic matter consists of the remains of formerly living organisms, plants and animals.

The decomposing bits and pieces not only provide nutrients for the plants but also help with the open space issue, no matter what kind of soil you're working with. In sandy soils, organic matter gets into the large spaces and helps hold the soil together. In clay soils, the organic matter clumps and creates more spaces for water and air. There are a lot of different ways to add organic matter to your soil, with manure and compost at the top of the list.

Fall is the best time to apply manure (fresh is OK if it you do it this way), working it into the soil; if you leave it lying on top, you'll lose the nitrogen, which will escape as a gas. Be careful about using poultry manure; it is exceptionally high in nitrogen and may cause root damage. If you apply manure in the spring, make sure it is at least 3 months old.

You can add compost to your garden in any season - just spread it in the garden or work it into the soil. Some composts can be used as mulches, some cannot The compost available from the University Area Joint Authority is an example of a compost that should not be used as mulch. lt is exceptionally dry and, if used as a mulch, will just suck the water out of surrounding plant material.

There are many other ways to improve your soil. One of the most effective soil amendments I've found for clay soil when planting or transplanting is a mixture of two parts compost, one part peat and one part bone meal. The amount depends on the size of the plant

For small annuals such as marigolds or zinnias, I use a handful; for larger plants, such as shrubs and trees, I use a lot more, enough to make up about one-third of the material that will be surrounding the roots. Double-digging new beds in the fall, although extra work, is a great way to improve clay soil. The exposure to below freezing temperatures in the winter will break up the clay particles, creating more pore spaces.

Darlene Weener; a Master Gardener from Boalsburg, is executive director of the ClearWater Conservancy.
For answers to your gardening questions, contact Master Gardeners by e-mail at centreext@psu.edu