MicTooriianisnis and Soil Conscrxation 



327 



biological pioccdurrs was liiiiitccl in scope and had little ai^plication 

 to practical agricnltnrc. • 



Microorganisms and Soil (x:)nservation 



The role of microorganisms in improxing the physical condition 

 of the soil. notal)l\ soil aggregation, has recently received consider- 



100 



90 - 



-5 80 



o 



Co 

 "D 



§ 60 

 o 



^ 50 



c 



^ 40 



a; 



Z 30 



a 

 o 



S 20 



10 







Plamfield sand 

 Spencer silt loam 

 Superior red clay 



r 



Aspergillus Penicillium Alternaria Fusartum StemphyUum Uporolnchum 



Mold species 

 Fig. 129. Influence of .specific fungi on aggregation of three soils treated with 

 alfalfa (from Gilmour, Allen, Truog). 



able attention. The strnctiire of the soil is greatly affected by the 

 m\'celium of fnngi and the slimy cells of bacteria, as well as by their 

 metabolic products. The effect of these consists in binding the loose 

 soil particles into water-stable aggregates. Various microorganisms 

 vary greatly in this respect. Whereas some bacteria have very little 

 effect, certain fungi, by means of their long hyphae, entangle the soil 

 particles into stable aggregates. The slimy substances, of a hemi- 

 cellulose or polyuronide nature, produced by various bacteria are 

 also highly effective in this respect. 



Addition of organic materials to the soil, notably glucose, starch, 

 straw, clover, and stable manures, favors greatly the state of aggre- 

 gation by favoring development of various groups of microorganisms. 



