The degree of acidity or alkalinity of the soil mass expressed in pH values or in words as follows:

          - extremely acid, below 4.5;

          - very strongly acid, 4.5-5.0;

          - strongly acid, 5.1-5.5;

          - medium acid, 5.6-6.0;

          - slightly acid, 6.1-6.5;

          - neutral, 6.6-7.3 (strictly 7.0);

          - mildly alkaline, 7.4-8.0;

          - strongly -alkaline, 8.l-9.0;

          - very strongly alkaline, over 9.1.