Soil

Bone meal has traditionally been used as a phosphorus source for flower bulbs, but you may want to reconsider. If your soil is healthy, you may not need it and you may be better off with a balanced fertilizer designed for bulbs or even nothing at all. The nutrient content of commercial bone meal is lower than in the past due to the cleaning process, and the bone smell may attract raccoons or dogs to dig up the bulbs.

Fava beans growing at our McClellan Ranch project

More Information: Choosing and Using Cover Crops

More information: Impact of Mulches

After harvesting remaining summer crops, add amendments such as blood meal, alfalfa pellets or fish emulsion to replenish nitrogen in the soil. Add a layer of compost to all existing garden beds to provide needed nutrients for winter crops. Be sure to leave some areas of native soil for ground-nesting bees.

For more information: Bagged Potting Mixes

When the plants are done in the containers, you can refresh the container soil without throwing it away. Start by loosening the soil and removing the plant parts. Then, add additional potting mix and some compost. The fresh material will add nutrients and organic matter for the next round of planting. Do not reuse the container soil if there have been problems with disease, insects, or weeds. Pathogens, insect eggs, and weed seeds can remain in the soil even after a plant is removed. 

More information: Gardeners can reuse, recycle last year's potting soil, Oklahoma State University Extension

An easy and environmentally friendly way to "lose the lawn" is to smother the grass and mulch at the same time. Place cardboard or several layers of newspaper over the area, overlapping by eight inches to keep weeds from finding openings. Wet the cardboard or newspaper, then cover it with 4-6 inches of compost, plant trimmings, or other mulch. Having wood chips on top will give it a neat appearance. The materials will gradually break down and improve the soil over time. New plants can be installed by cutting an X in the cardboard or newspaper and placing the plants right through the mulch. UC Davis Arboretum Horticulturist Stacey Parker's website shows you how it's done.

Many home gardeners are confused about the terms “compost” and “mulch;” frequently these terms are used interchangeably, but they are not really the same thing. Here is a Comparison of Soil and Mulch from UCCE.

Amend soil with compost to create soil that will retain water but still drain well enough for roots to have the air and water they need.

Benefits of compost
- Forms aggregate particles with clay
- Creates larger pore spaces for water & air
- Helps release nutrients from clay so that plant roots can absorb them
- Supports the soil foodweb by providing nutrients for the organisms
- Lowers pH somewhat.

Benefits of mulch
Mulch does not get worked into the soil. It sits on top of your irrigation system and helps:

- Control weeds
- Prevent erosion
- Preserve soil moisture
- Keep roots cool and moist

Soil solarization can be used to control diseases, nematodes and weeds by baking everything under plastic sheeting.The best time for solarization of soil is from June to August. Transparent or clear plastic is the best choice. Leave the soil covered for 4 –6 weeks. Refer to the UC Pest Note on Soil Solarization for Gardens & Landscapes.

Even a warm April day doesn’t mean your soil has given up its winter chill. Planting in cold soil results in slow germination, increased risk for rot from damping off, and even stressing plants for the rest of the season.

You can use a soil thermometer to check soil temperature directly by following the instructions provided here. UC lists soil temperature conditions for vegetable seed germination, or use our vegetable planting chart to look up the months best suited for planting.

The clay soils which dominate our area are particularly susceptible to compaction, especially when they have received a lot of rain. These soils are characterized by small mineral particles. Hence squeezing out the air spaces makes it more difficult for plant roots and soil organisms to get the oxygen they need to flourish. Try to avoid walking on or using heavy equipment on soil that is wet. Digging in wet soil can also destroy the structure, breaking up useful soil aggregates and earthworm tunnels. Try to wait until the soil is moist, not wet or dry, for easiest tillage. If you must walk or stand on the soil, use a board to distribute your weight over a broader area. Mulch can also create a bit of a cushion and help minimize compaction.

Before adding fertilizer or soil amendments to your garden, first find out what your soil really needs by conducting a soil test. Knowing your soil’s pH value is important in determining which plants will thrive or struggle in your soil. Understanding the levels of nitrogen, phosphorous, and potassium in your soil will tell you which nutrients are abundant and which are lacking. Don’t overfertilize – excess nutrients can pollute local waterways. Commercial soil testing labs provide the most thorough results, but several home kits can give you a good baseline. Test soon and be ready for spring planting.

Worm composting, also called vermiculture or vermicomposting, is a convenient way to decompose kitchen waste and provide nutrient-rich soil amendments for your vegetable garden.

The Santa Clara County Home Composting Education Program offers:

• Worm workshop classes
• Sources for worms