42 HARNESSING THE EARTHWORM 



soil to the acre each year, and they thrive especially well in moder- 

 ately acid to moderately alkaline soils. One of the many indica- 

 tions of potentially productive soils is the presence of well- 

 nourished earthworms. 



From the Journal of Forestry, Vol. 37, No. 1, we quote the 

 following from the article on "Forest Soil in Relation to Silvi- 

 culture," by Svend O. Heiberg, Associate Professor of Silvicul- 

 ture, New York State College of Forestry. The quotation refers 

 to one main type of forest soil, "mull," or "crumbmull" : 



In the mull, the organic matter is intimately mixed with the 

 upper few inches of the mineral soil. In its best form it is 

 crumbly, friable, and porous. It resembles a well-cultivated gar- 

 den. The mixing is done by the soil fauna, especially by the 

 earthworms which continually dig and cultivate and eat both the 

 vegetable matter and the mineral soil. The excreta are placed 

 upon the soil surface; in fact, the entire humus layer of coarse 

 mull constists of earthworm excreta. In good forest mull between 

 one and two million earthworms are found per acre, weighing 

 about 800 pounds; their castings may amount to 15 tons per acre 

 per year. There is no doubt that earthworms are the most bene- 

 ficial animals in forestry. The cultivation of the soil and plough- 

 ing under of manure which farmers and gardeners find to be of 

 great importance for the soil productivity is done "free" by the 

 earthworms if they are furnished with a suitable environment . . . 

 With respect to productivity, this humus type (coarse mull) is 

 undoubtedly the highest and its ability to absorb moisture and 

 chus prevent surface run-off and erosion is high. One liter of 

 water poured on a 100 square centimeters surface of coarse mull 

 which corresponds to about four inches of rain may be ab- 

 sorbed in less than 15 seconds, while on the same soil where the 

 coarse mull has not developed it may require two or three hours 

 to seep in. 



MASS-PRODUCTION OF TOPSOIL 

 ON FARM LAND 



To show just what the earthworm can accomplish in soil- 

 building when given a proper chance, we must select a spot in the 

 world where nature has provided a favorable environment, with 



