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The dirt on dirt Materials such as finished compost, left, and raw organic material, right, can help make the Rogue Valley?s soil better for growing plants, says Denny Morelli, a soils specialist with the Jackson County Extension Service. Mail Tribune / Bob Pennell Mail Tribune Bob Pennell Saturday Apr 17, 2004 at 2:00 AM Feb 16, 2011 at 9:49 AM JOHN DARLING,for the Mail Tribune Caring for Southern Oregon's many types of soil isn't as simple as many gardeners believe Rogue Valley soils have been called a lot of names ' exotic, challenging and just plain tricky You don't just stick seeds in and water them. You have to study and master the dirt here, using strategies developed by the masters. For starters, the Rogue Valley has two distinct types of soil, said professor Rich Roseburg of Southern Oregon Extension Service ' porous, granitic soils on the west side and sticky, difficult-to-work-with basaltic clays to the east. You'll also find some sandy soils, the best in the area, in creek bottoms. The granitics don't hold much water, so they take more irrigation. They also tend to lack potassium and phosphorous, so they like manure, which should be amended into soil over a decade. The clays are rich with potassium and phosphorous but like to be made workable with compost, he said. In building soil, you first have to realize the truth is that old saying, Feed the soil, not the plants, said Master Gardener Denny Morelli, a soil health and compost specialist and instructor at the Extension Service. For plants to thrive in your soil, it needs lots of organic matter to feed soil organisms ' bacteria, fungi, protozoa, earthworms ' because they are the only things responsible for converting raw nutrients into plant-available forms, said Morelli, who conducts soils research on his Sardine Creek farm east of Gold Hill. These are particularly hungry soils, he said. Soil organisms hold moisture and nutrients, which they time-release, he said, and they build channels supplying plant roots with air. The first step toward determining what your soil needs is testing its content. Testing kits are available at many garden stores, and the county Extension Service also tests soil. Nitrogen, potassium and phosphorous are the basic elements necessary for absorption of nutrients. Carbon dioxide levels, measured in some tests, tell you the degree of organic decomposition in your soil as it progresses toward stable and desirable humus, which emits little CO2. The pH (potential hydrogen) test determines the amount of nutrients in your soil that are actually available to plants because in this area they absorb nutrients only if soil is in the 6.5 to 7 pH range, Morelli said. Most are in that range naturally. Amendments that increase nitrogen content include bloodmeal, stock manure, soybean meal and bat guano. Kelp is good for increasing dirt's potassium level. Phosphorous-hungry dirt likes colloidal phosphate. If a lot of CO2 is being emitted, you can accelerate the decomposition of organics in your garden by adding manure, which is rich in nitrogen. The pH can be raised (made more alkaline) by adding lime, but lowering pH is difficult, like trying to take the salt out of soup, Morelli said. However, adding small amounts of acidic ingredients like sulphur, alum, oak leaves, pine needles or tree moss will help. The care and handling of soil is as important as what you amend it with ' and this means proper mulching, use of raised beds and tilling our delicate soils with care, if at all, he said. Raised beds provide a contained habitat in which to concentrate the energy and nutrients you're putting into the soil and feeding to the organisms in it. Mulch with compost (the best, as it is already decomposed and contains the most nutrients), alfalfa hay (lots of nitrogen), straw or shavings, but not grass hay, which is crammed with weed seeds. Mulching helps retain moisture, which tends to get scorched out of Rogue Valley soils by extreme summer heat and wind. It lessens winter drowning (and compacting) of soils, shields against frost and provides nutrients. Morelli's 18 years of soils research on Sardine Creek (We could hardly get anything to grow when we got here) has led him to challenge some long-held gardener myths, chief among them that tilling is good for soil because it loosens things up and mixes in amendments. It's not good for soil, he said. Tilling actually harms soil by collapsing (air) channels and compacting the dirt. It breaks up aggregates, the tiny clumps that hold nutrients and moisture for timed release. It breaks up soil crust, kills earthworms and mixes in weed seeds sitting on the surface. Tilling, he said, is good when you establish new gardening areas and want to mix in amendments at the start. After that, amend with compost-mulch. Another myth is that plots should lay fallow, Morelli maintained. It has to be fed by growing a cover crop like legumes, rye or buckwheat ' and also mulched or it will dry out. Mary Danca of Ashland has put Morelli's principles to work in her clayey Ashland soil, to which she adds compost. The soil here isn't as bad as people say, Danca said, but then I'm following all the rules, composting my green kitchen waste with worms to break it down and gently mixing it in without tilling the soil. You don't want to upset the soil and upset the natural order of things. That's the key. The peas, beans and lettuce are already coming up real nicely.Soil should be tested The first step in building healthy soil is to get it tested, and at least two tests are available in the Rogue Valley. Gardeners can drop off a soil sample at the Jackson County Extension Service office and have dirt tested for pH balance and nitrogen, phosphorous and potassium content for & 36;15. Soil samples are sent to Josephine County for testing. Master Gardeners also will offer the service at the Master Gardener Spring Fair April 24 and 25 at the Jackson County Exposition Park in Central Point. The spring fair test can be done while gardeners wait. Gardeners can get the same soil contents tested, plus tests for carbon dioxide and ammonium, at their homes by calling Denny Morelli, a soil health and compost specialist for the Extension Service, at 855-7416 (e-mail [email protected]). The cost of the on-site tests is & 36;45.