TECHNICAL DISCUSSION 157 



Stockli (10) studied the effect of earthworms on the soil in 

 ten different places including garden, meadow, and forest soils. 

 He found great variations in their activity from place to place 

 and from season to season. Temperature and moisture were all 

 important; geological origin of the soil was of no consequence. 

 In comparison with the undisturbed soil, the casts and the linings 

 of the tunnels had, in general, higher pH and loss-on-ignition 

 values, higher content of humus soluble in 30 per cent EbCb, and 

 higher bacterial count. 



Using a noncalcareous loamy clay, not ordinarily occupied 

 by worms, with which were mixed 1 part calcareous sandy soil 

 to 9 parts of the loamy clay, and finely cut leaves and stems of 

 Lactuca sativa, Puh (6) introduced earthworms. (Pkeretima buc- 

 culenta) and left them for two months. At the end of this time 

 the casts covered virtually the whole surface. Her analyses of 

 the soil and of the worm casts at the end of this period were as 

 follows : 



Parent Worm 



Soil Casts 



pH (noncalcareous loamy clay) 6.2 6.8 



pH (noncalcareous loamy clay, with calcareous 



sand) 6.4 6.7 



8.5 7.4 



pH (calcareous loamy clays) 7.8 7.5 



8.0 7.2 



Base capacity per 100 gm m.e. 21.0 



Exchangeable calcium (CaO) per 100 gm..m.*. 17.8 17.8 



Available phosphorus p. p.m. 37.3 



Available potassium p. p.m. 193.0 294.0 



Ammonia nitrogen p. p.m. 33.0 49.0 



CaO P*r cent 1.95 2.37 



Total nitrogen per cent 0.054 0.151 



Organic matter percent 1.20 1.52 



Lindquist (4) reports that earthworms increase nitrate pro- 

 duction not only by mixing humus with mineral soil and stimu- 

 lating bacterial activity but also through the decomposition of 

 their own bodies. 



