Effects of oxalic acid and lime on the enchytraeid Cognettia sphagnetorum (VEJD) in mor humus

A two-factor orthogonal plan of experimental design was used to estimate a coupled influence of oxalic acid and lime on the enchytraeid Cognettia sphagnetorum in mor humus. Calcium carbonate (X ₁ ) in doses of 0, 300 and 600 mg per 10 g dry wt of mor humus and oxalic acid (X ₂ ) in doses of 0, 45 and 90 mg were added in accordance with the plan. Enchytraeid number (initial number — 50 per container) after three weeks of experiment was maximal at the medium calcium carbonate dose and absence of oxalic acid and minimal at the highest doses of the compounds. Influence of the compounds on the enchytraeid number (Y) is described by the second order equations: $$Y = 23.4 - 3.3X_1 - 6.8X_2 - 3.4X_1 X_2 - 7.7X_1 ^2 + 1.8X_2 ^2 {text{ (in coded form) and}}$$ $$Y = 24.4 - .051X_1 - .157X_2 - .00025X_1 X_2 - .000085X_1 ^2 + .0009X_2 ^2 {text{ (in natural form)}}$$ (in natural form). Negative effects of heavy liming can not be explained only by pH changes.