Alameda Sun, Thursday, December 10, 2020
by Marla Koss, ABG Board member
When the first day of winter is not long off, gardeners in harsh-winter areas may get a guilt-free pass to ignore the yard in favor of the cozy indoors, but those who grow backyard vegetables and fruit in mild-winter climates get no such pass. For Alameda gardeners with fast-draining, sandy loam, there is one more task on top of everything else: late-fall soil amendment. If growing great tomatoes is a goal, a crucial first step is nourishing the soil now where next year’s tomatoes will grow. Slow-release nutrients so necessary for good plant growth will be better available to new plantings next year, if dug in the garden before winter truly settles in.
Few know how to solve local gardening dilemmas better than the staff at locally-owned nurseries. When quizzed about late fall soil prep, Encinal Nursery owner Greg Dupuich and Jeff Bridge, General Manager of Ploughshares Nursery gave the same immediate response: “green manure.”
In layman terms, that means broadcasting mustard seeds or planting fava beans that will grow over the winter and be tilled into the soil a month or so before spring planting. Both Bridge and Dupuich also emphasized the importance of adding humus for soil structure and beneficial microbes such as mycorrhizal fungi to support the living network in garden soil.
Keys to soil success
Know your soil composition: Have it tested, or learn to test it with do-it-yourself, at-home methods. A pH soil meter that inserts into the soil via a prong can be very helpful (and, like its sister, the moisture meter, actually fun to use). Neutral, and therefore ideal, soil pH is 7.0; many garden vegetables like tomatoes prefer a pH of 6.5 to 7.0. If your soil is too acidic or too alkaline, certain nutrients cease to be bio available to growing plants, so adding the wrong amendments could bring on poor results if the soil’s pH level is a mystery. In any case, home-made compost, which by nature is pH neutral, can be the most economical soil booster, and can benefit any garden year-round.
Nitrogen, phosphorus and potassium (NPK): Be careful not to add too much nitrogen to the soil at this time of year. The phosphorus ratio should be as high or higher in relation to nitrogen, with potassium secondary (an example of one brand of bone meal is labelled as 1-15-0). Adding phosphorus in the form of soft rock phosphate (if the soil pH is lower than 5.5) or bone meal will spur rapid, strong root formation when tomato or vegetable starts are finally planted.
Soil quality
The ideal soil structure consists of 25% air, 25% water, 5% organic matter, and 45% mineral matter. Humus can help bulk up soil structure and allow enough air to be present in the soil; chicken manure is an excellent alternative to commercial humus. Commercial humus and chicken manure can be found in 2 cu. ft. bags at the nursery; both contribute small amounts of NPK to the soil as well as beneficial soil microbes.
Calcium is an especially necessary micro nutrient and leaches readily out of sandy soil. Agricultural Lime (dolomite) is a natural source of calcium and magnesium — both of which are in short supply in Alameda’s dirt. Use it to boost tomato plant health in slightly acidic soil.
Ground Oyster Shell (calcium carbonate), is an organic product that also raises soil pH; it provides a steady release of nutrients long-term, but may take a year or two before it is fully bio available. Gypsum (calcium sulfate) more quickly releases calcium ions into the soil than calcium carbonate does, and does not raise soil pH. Many home gardeners save up eggshells to grind in a blender and add back into the garden when planting tomatoes; adding eggshells in late fall gives them time to break down for more efficient utilization come spring planting than waiting to sprinkle them in during planting time.
Complete organic fertilizers offer an easy alternative and can be used in place of two or more amendments or planting a cover crop.
Choose one or more amendment options to put to work right away. Perhaps adding a form of calcium to the patch before planting fava beans (be sure to keep them watered if the rains don’t come) sounds best. Or digging in a complete fertilizer, adding bagged humus or chicken manure to the patch along with bone meal. Work any of these amendments in to a depth of 6 inches.
Local nurseries
Encinal Nursery carries the E.B. Stone organic line of fertilizers and amendments, fava bean seeds, and mustard seeds and is located at 2057 Encinal Ave. Call (510) 522-8616 for information. The nursery is open 10 a.m. to 5 p.m. daily and closed on holidays.
Ploughshares Nursery sells G&B Organic Amendments and fava bean seeds and is located at 2701 Main St. Call (510) 755-1102 for information. Ploughshares is open Wednesday through Sunday 10 a.m. to 5 p.m. They will be closed Dec. 18 and from Dec. 24 to Jan. 2, 2021.