Saturday, April 26, 2014
Gardening, whether flowers or vegetables is probably one of the most rewarding experiences I’ve encountered. At first it can be a little intimidating. There are a lot of factors to consider, but gardening becomes easier to understand through experience. Problem solving garden issues one year enables recognition and corrective actions the next. Most gardeners go through this learning process and it’s actually fun to discover new things. Understanding soil will get your first gardening experience off to a good start; after all, soil is the foundation for any successful garden.
The most common issue I see are problems with soil pH. Depending on whom you ask pH stands for either “power of Hydrogen” or “potential Hydrogen.” It’s just one of those technical scientific controversies not pertinent to our needs right now. It is enough to know that pH represents the balance of acidity and alkalinity. It is that balance that determines the availability of nutrients.
You can find pH charts online that will show a typical range from 0 to 14, with 7 being neutral – an equal balance of acid and alkaline. Most garden plants thrive in the 6.0 to 7.5 range because that is the place where most of the nutrients a plant needs are easily dissolved and available for uptake. I personally prefer my soil to not go beyond 7.0 for a little wiggle room. I have clay soils which are naturally 7.0-7.5 in places and I found out by experience that I can easily exceed that balance by what I apply to my soils.
When soil is too acid (less than 7) or alkaline (more than 7) certain nutrients are more strongly bonded to the soil. For instance, when pH exceeds 7.5, iron, manganese, and phosphorus are less available, while below pH 6.0, nutrients, such as nitrogen, phosphorus, and potassium, are less available.
That is why before planting it is critical to know the soil pH of your garden. Turning the soil, adding compost, nutrients, and top dressings can all have an effect on soil pH. When looking at a pH chart you can see the band for nitrogen begins to thin after 7.0. The wider the band on the chart the more available nutrients are. It is also critical to know the pH of your compost before applying.
There are aids available at garden stores that can give a rough idea of your soil pH. The Master Gardeners can also test for soil pH during clinics. You can call OSU Extension at 541-296-5494 to find out their clinic schedule.
Soils high in organic matter are teaming with a whole host of macro and microscopic critters critical to nutrient cycling. Soils low in organic matter will not. Why? There isn’t any food for them. Dry soils even less. The best known soil critters are worms. Worms feed on large organic matter and release nutrients as they travel through the soil. Their burrows also contribute to better soil drainage. Worm castings and other arthropod leavings are in turn broken down into tinier particles by smaller soil microbes, theirs by even smaller. It is this process that creates the nutrient cycle from animal to plant.
Soil that is freshly broken activates a frenzied release of tied up nutrients the first year. Once the organics are used up they must be replenished. This is why a lot of new gardeners can experience great success the first time they garden.
Other important soil inhabitants are fungi. Fungi are involved in making nutrients available that the plant might not be able to otherwise get. In return the fungi get sugars from the plants roots. Mycorrhizae fungus is highly beneficial to forest species and create huge underground networks between trees. The pro is that there is a continual passage of nutrients; the con is that a disease of one tree can be more readily spread to others by this same network. Glomalin, a water-soluble protein produced by mycorrhizae, glues particles within the soil together and has a stabilizing effect on soil aggregates.
Soil disturbances, such as tilling and spading have detrimental effects on soil critters and fungi. Besides killing them, burrows and feeding pathways are destroyed, and soil aggregates are broken up. Once the initial ground breaking and garden prep has occurred, it is best to forgo any future tillage and spading and just keep adding organic material to the top of the soil throughout the year. This will keep moisture in, keep the soil critters fed, and help prevent rain compaction. Organisms feeding on the compost will carry nutrients deep into the soil where they will be available for uptake by plants. Also, not all compost is created equal so there may be a need for additional nitrogen applications.
In closing, remember – pH, soil microbes, fungus, and compost for healthy garden soils.
Shilah Olson is with the Wasco County Soil and Water Conservation District.
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