By: Claire Murray

Last Weekend for Explorit's Exhibition "How Does My Garden Grow."

Have you been enjoying fresh garden vegetables all summer? Ever wonder what type of soil is best for your garden and those tasty veggies? Is one kind of soil better for root crops like carrots, parsnips, potatoes or beets, than for leafy plants like lettuce, kale, swiss chard or basil?

This weekend is your very last chance to explore these and other questions relating to how air, light, water and soil enable plants to grow, at Explorit Science Center's exhibition, "How Does My Garden Grow?"

At Explorit you and your children will discover what and why soil quality is so essential to a bountiful garden. Soil is mostly a mixture of weathered rock and mineral particles which have been broken down over hundreds of thousands of years. Come to Explorit by October 3rd and try your hand at making your own soil!

Take about 50% of this mineral matter, mix it with approximately 25% air, 20% water and 5% organic matter and you end up with a good quality soil. Depending on the particle size of these minerals you can have a soil ranging from very sandy to a very dense clay soil. Sand is generally found to be the largest particles in soil compared to those of the microscopic sized particles of clay.

Here is a simple test that many soil scientists use to see what kind of soil you have. Dig a hole at least 2 inches deep; take some of that soil and, with your hands, try to form a ball. The general rule is if you have difficulty forming a ball, because it doesn't stay together, the soil has a high sand content. On the other hand, if the ball is sticky and creates a firm ball that does not fall apart when tapped, the soil generally has a high content of clay. (Another indicator of high clay content is if the soil is so hard and dry you can barely break it up).

The perfect medium between these two soils is called a loam soil. When performing the ball test, a loam will easily form a nice ball and when tapped several times will crumble.

Sandy soils tend to be less fertile than those with higher clay content. With lower water holding capacities, sandy soils are leached of nutrients and water at a faster rate. However, due to low compaction rate, sandy soils are loose and airy allowing the roots of plants (especially tubers and tap roots) to easily grow and push through the soil.

On the other hand, you will find soils with high clay content showing the opposite properties: they retain water and nutrients and tend to be more compact with less air throughout the soil. Water molecules are attracted to the microscopic clay particles, thus creating a high water holding capacity.

With any soil type, one of the best ways to improve texture, water holding capacity and structure is to add organic matter. Anyone can do this by simply adding compost, peat moss, saw dust or manure.

Soils in the Davis area tend to be heavy clay, which would benefit highly from the addition of gypsum (80 lbs. per 100 sq. feet), to initially break-up the clay, and lots of compost.

Becoming familiar with the kind of soil in your garden enables you to improve your soil for optimum growing. This knowledge will also tell you about which types of plants/vegetables are best grown in your garden. So don't miss out on sharing these concepts with your children through Explorit's hand-on science exhibition "How Does My Garden Grow".

Remember, October 3rd is the day to visit this exhibition. Keep your eyes out for Exploit Science Center's next exhibition, "Leave it to Levers...and Other Simple Machines," running from October 9 through December 5, 1999.

------------------------------------------------------

Explorit Science Center is located at 3141 5th Street in East Davis. The current exhibition is How Does My Garden Grow? Public hours are Saturday from 11:00 a.m. to 4:30 p.m., Sunday from 1:00 to 4:30 p.m., and Tuesday through Friday from 2:00 to 4:30 p.m. Regular admission is $3; members, teachers (with school ID) and children under 4 are free.