Soil Quality measures the Electrical Conductivity (EC) of soil and growing media.
At a given temperature, the EC of any growing media is relative to the amount of nutrients - an increase in nutrient produces an increase in Soil Electrical Conductivity. Temperature is a factor that which affects the EC level. The higher the temperature the higher the EC. Most EC agricultural standards are given at 25°C. As a rule of thumb, the EC of water increases by 2 to 3% for each increase of 1°C.
To capture nutrients in the growing media, a plant needs water so minerals can be dissolved in water and be available as nutrients to the plant. In a dry growing medium a plant will not be able to grow and capture any nutrients. EC is also affected by the soil moisture: when the soil is dry, the EC greatly drops even if there are minerals available.
Comparison of Nutrient level in time or between different samples should be done based on the same moisture level and temperature.