In the Bah! Humbug! post, I explained why there is not any information gain by doing a water-based extraction and comparing those nutrient concentrations with results from a conventional soil test. To do a paste extraction and call those the "available" nutrients is redundant; the technical term for a soil test is a soil nutrient analysis, which gives us a nutrient availability index.

There seems to be a misapprehension that nutrients in the soil can be present but not available. But that question of availability is exactly what soil tests do. They measure how many nutrients are extracted, one compares those results to guideline levels, and determines if the nutrient is required as fertilizer or not. All the information one needs to determine if availability is at an adequate level is already included in the conventional soil test. 

These explain further.

• The unambiguity of nutrient availability indices
• Bah! Humbug! Why the concept of "exchangeable" vs. "available" nutrients is a fallacy
• "If you want to use soil test results to develop a fertilizer program, use a different extractant"
• "Available" calcium, soil pH, and fearmongering
• A fertilizer miscellany: cost, phosphite, and nutritionism
• Calcium deficiency in turfgrass, an imaginary problem?