Effect of pH and calcium content of soil on earthworm cast production in the laboratory

Abstract

The relative importance of pH and Ca content of soil in determining cast production by Allolobophora caliginosa (Savigny) was evaluated by a mini-frame technique using soil to which increasing amounts of four inorganic Ca salts were added. Whereas soil pH increased with the addition of increasing amounts of CaCO 3 and Ca(OH) 2, it remained constant with increasing amounts of CaSO 4 and Ca(NO 3) 2. Over the range of values studied, cast production increased with increasing pH and Ca level but did not increase with increasing Ca when soil pH was constant. Decreases in cast production were obtained above pH 7.3 with CaCO 3 and above 6.7 with Ca(OH) 2. Separate studies suggested that a high osmotic pressure of the soil solution resulting from the addition of high levels of soluble Ca(NO 3) 2 was responsible for the dramatic decrease in cast production obtained with this salt. The present study has provided useful methods for related studies of the effect of a range of fertilizer materials on earthworm activity.