Elisa Shackelton: Time to test your soil


— As we all are getting eager to be outside again gardening and working in the yard, it would be wise to get a soil test done before you do any new plantings in order to maximize your success rate as well as your investment in seeds or plants, water and time - and perhaps to also decrease your level of frustration when plants don't do as well as you'd hoped because of poor soil preparation.

The Colorado State University Soil, Water and Plant Testing Laboratory analyzes soil, plant, water and manure for farmers, homeowners and researchers. The results of soil, water and manure analyses form the basis for fertilizer recommendations and reclamation of salt- and sodium-affected soils. In the home garden setting, soil testing is valuable to establish a baseline on soil limitations related to pH, salt levels and the need for phosphate and potash fertilizers. A standard soil test typically includes the following: texture, organic matter, pH, lime, soluble salts, nutrients, nitrate nitrogen, phosphorus, potassium, micronutrients such as copper, iron, manganese and zinc. Additional tests could be run for special needs such as lead content or sodium problems.

Got good tilth?

Another factor that affects a healthy landscape or garden is the tilth of the soil. The term tilth refers to the soil's general suitability to support plant growth or, more specifically, to support root growth. Tilth is technically defined as "the physical condition of the soil as related to its ease of tillage, fitness of seedbed, and impedance to seedling emergence and root penetration." A soil with good tilth has large pore spaces for adequate air infiltration and water movement. It also holds a reasonable supply of water and nutrients.

Managing soil tilth

• The major limitation of sandy soil is its low capacity to hold water and nutrients. Plants growing on sandy soils don't use more water; they just have to be irrigated more frequently and with smaller quantities. The best management practice for sandy soils is routine applications of organic matter. Organic matter holds at least 10 times more water and nutrients than sand. Sandy soils with high organic matter content (up to 5 percent) make an ideal soil.

• The limitations of clay soils arise from a lack of large pore spaces, restricting water and air movement. Soils easily waterlog when water can't move through the soil profile. The best management practice for clay soils is routine application of organic matter and attention to fostering the activity of soil microorganisms and earthworms. As soil microorganisms decompose the organic matter, the tiny soil particles bind together into large clumps, increasing large pore space. This improvement takes place over a period of years, so a single, large application of organic matter won't do the trick.

• On clay soils, also take extra care to minimize soil compaction. Soil compaction reduces the large pore space, restricting air and water movement through the soil, thus limiting root growth. An easy way to reduce garden soil compaction is to establish designated walkways.


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