Microorganisms and Soil Conservation 



329 



added; this suggests the probabihty that other cementing substances, 

 such as chiy and hunuis, play essential rolffs in this process, as shown 

 recently by S^^'ab\'. 



The inoculation of soil with fungi, such as Trichoderma Ugnorum, 

 to improve soil structure has been recommended. Such inoculation 

 is effecti\e, howcNcr, only when accompanied by addition of freshly 

 decomposable organic matter to the soil. 



Table 73. AtiCiUi-ujATiNc; Ei^'fect of MicitooiuiANisMs upon Various Silt and Clay 



Fractions of Collington Sandy Loam with Complex Organic Materials as 



Energy Sources (from Martin and Waksman) 



* All organic materials used in 2 per cent concentration. 

 t Ag = Percentage aggregation. 



Gilmour, Allen, and Truog concluded that inoculated soils to 

 which no organic materials had been added underwent only a slight 

 to moderate degree of aggregation. On the other hand, the addition 

 of oat straw and alfalfa decreased considerably the percentages of 

 unbound silt and clay in the soils studied. When no fungi were 

 present, there were lesser decreases in the unbound fractions. In 

 the presence of alfalfa and fungi, there was a marked reduction in 

 the susceptibilities of the soils to erosion. The effectiveness of fungi 

 in the aggregation process was related to the ejffectiveness of the in- 

 dividual organisms, the type of organic matter, and the physical 

 composition of the soil. 



