RELATIONSHIP BETWEEN NEUTRAL SUGARS AND THE DEGREE OF HUMIFICATION INANDISOLS

We investigated the relationship between the amounts of neutral sugar carbon (NSC) and total carbon content (TC) or the degree of humificati on of soil organic matter (SOM) using 14 Andisols in Japan. The amount s of 7 kinds of NSC, TC content and the degree of humification of humi c acids expressed as RF values were determined. Positive linear correl ations were observed between the amount of every kind of NSC and TC. E specially the amount of mannose carbon which was likely to be adsorbed on the mineral components in soil and is considered to be mainly of m icrobial origin was highly correlated with TC (r=0.912*). However the correlation of cellulose-type glucose-C which was assumed to be mainl y of plant origin was less significant (r=0.603) compared with other kinds of NSC. The proportion of total NSC (TNSC) in TC was negatively correlated with RF values (r=-0.623). Furthermore the proportion of T NSC in humic acid carbon was also negatively correlated with RF values (r=-0.891*). In a conclusion, our study showed that; 1) Neutral suga rs accumulate along with the increase in the accumulation of SOM. Howe ver the relationship seems to be influenced by different rates of accu mulative characteristics in each sugar. 2) The lower the proportion of neutral sugars in SOM, the higher the degree of humification. On the other hand, we could not determine whether plant material origin or mi crobial product origin was more responsible for the phenomenon obserbe d.