Effect of difference in fumigation period on the accumulation of ninhydrin-reactive compounds in Japanese Andosols

Abstract

Since ninhydrin-reactive nitrogen (NRN) reacts with a small fraction of the total amount of soluble organic N such as α-amino compounds (amino acids peptides, and proteins) and also ammonium, it is an appropriate reagent for the determination of soil microbial biomass. Further studies on the ninhydrin-based assays are, however, required to elucidate the mechanism of NRN autolysis in different soils. In the present study, we investigated the relationships between biomass N (BN) and NRN after 24 h and 240 h of CHCl3 fumigation in a range of Japanese Andosol Soils. Our results showed that 240 h fumigation provided 1.9 times more NRN (n = 11), which mostly consisted of NH4 +-N. The relationships: BN = 4.31 × NRN and BN = 2.01 × NRN are considered to be appropriate for 24 h and 240 h fumigations, respectively.