According to the California Master Gardener handbook, soil is composed of sand, silt and clay mineral particles in varying proportions. It’s a soil’s tilth — its texture — that determines how well plants grow and the ease with which plants are able to take up water and nutrients.
There are 12 basic soil types recognized based on the USDA Classification system, but we’ll concentrate on the most common: loamy sand, loam, clay loam, and clay.
You can determine soil texture by using the feel method. Take a handful of moist soil from the area that you will be planting. Squeeze it so that it forms a clump or ribbon. No ribbon can be formed with loamy sand without breaking. With loam, a short ribbon can be formed; it will split easily and break away when about half an inch long and can be easily handled. Clay loam will form a strong ribbon when moist, will break when it’s about ¾-inch long and can bear moderate handling. Clay forms a strong ribbon, will often break only after more than 1 inch and can bear considerable handling.
Once one determines a soil’s tilth, one can amend the soil for optimum planting results.
I had compacted clay, so I concentrated on adding organic matter.
After tilling the area, 10 cubic yards of compost were added. The Tracy Materials Recovery plant sells compost to Tracy residents for $5 per yard. Delivery is available for a minimum order of 10 yards, for a fee.
Once the compost was worked into the soil, I planted cover crops. I started with hairy vetch in fall, which was allowed to over-winter, then was tilled into the soil the following spring.
Field peas were sown in spring, then tilled into the soil during the summer. Cowpeas were sown in the summer and tilled into the soil in the fall. In this way, I added natural nitrogen and organic matter into the clay soil, increasing its tilth.
Recommendations for other soil types and a wealth of other information can be found on the University of California’s California Garden website, http://ucanr.org/sites/gardenweb/ — click on “Gardening Basics.” Gardeners can also call or visit the San Joaquin Master Gardeners office for help at 2101 E. Earhart Ave., Ste. 200, in Stockton.
• The Green Thumb is a column by Tracy’s master gardeners. University of California-certified master gardeners are available to answer gardening questions from 9 a.m. to noon Tuesdays, Wednesdays and Thursdays at 953-6112 or firstname.lastname@example.org.
• Editor's note: An earlier version of this column included incorrect information about the pricing of compost at Tracy Materials Recovery. The column also appeared in the Jan. 13 print edition of the Tracy Press, on Page 25. The Press regrets the error.