If you read the previous post on plant/soil progression you may be wondering why it matters. Well to start we can use it as a quick, visual assessment of where we need to begin our work to revitalize our chosen plot.
Begin by carefully examining your plot visually. Note and try to identify some of the most common plants and insects. Try to uproot a few plants to see if there are worms, or subterranean insects as well. With a little knowledge and experience the plants and insects can tell you a lot about the soil you're starting with. For example weeds like plantain weed (the herb not the banana-like fruit),usually indicate a compacted and hard soil lacking in organic matter and microbial diversity. Dandelion, and thistles will often indicate a soil with low nutrients and minerals and a lack of organic matter. Ants like dry well drained soils, their presence in large numbers indicates a lack of water holding capability and organic matter.
With this knowledge in hand we can begin some early planning and taking preliminary actions. Starting to collect organic matter to compost, gathering straw or wood chips for a deep mulching, planning irrigation systems if needed...
At this point I tend to look at a soil nutrient test with a preference for a mehlich 3 test. We aren't really looking here for total nutrients or minerals but ratios of nutrients. And the CEC (carion exchange capacity). CEC Is a measure of how many nutrients a soil is capable of holding onto. Properly reading these tests and assessing ratios is well betond the scope of a blog post. I recommend The Intelligent Gardener: Growing Nutrient Dense Food as an excellent book to read.
I do like the idea of doing a biological assessment but not yet. My preference is to begin by balancing nutrient imbalances then adding my compost and mulch and keeping it moist for a few weeks. Mulch, compost and organic matter all bring with them microbiology, doing the test too soon tends to give a skewed result, whereas allowing them to reproduce and grow a while first tends to give a little truer assessment. Unless you're well trained in microscopy have your soil and/or composts tested by a reputable lab. For our USA readers I recommend Microbes In My Soil as a reputable lab with reasonable pricing.
Planting cover crops will help boost biology, plants feed microbes with root exudates, microorganisms begin retrieving nutrients for plants. Legumes (peas, beans and clover as examples) as cover crops add plant available nitrogen to the soil, they for relationships with bacteria that take nitrogen from the air and make it available to plants in the soil. Nitrogen is a major nutrient needed for healthy growth and lush green leaves.
Using visual cues and combining them with scientific testing with the knowledge to use both is a sure fire path to organic growing success.