Contribution of bacterial cell nitrogen to soil humic fractions

Abstract

Fulvic acid Humic acid tion Serratia marcescens KEY WORDSHumoprotein 15N_bacteria lcells Organic matter fractiona-SUMMARY Living cells of Serratia marcescens, uniformly labelled with ~ 5N, were added to samples of maple (Acer saccharum) and black spruce (Picea mariana) forest soils. After different periods of incubation from zero time to 100 days, the soils were subjected to alkali-acid and phenol extraction to provide humic acid, fulvic acid, humin and 'humoprotein' fractions. Significant amounts of the cell nitrogen were recovered in the humic and fulvic acids immediately after addition. After incubation, less cell nitrogen appeared in the humic acid and more in the fulvic acid. The amount of cell nitrogen recovered in the humin fraction increased with incubation. Roughly 5 to 10 per cent of the added cell nitrogen was found as amino acid nitrogen from humoprotein in a phenol extract of the humic acid. The data are consistent with the occurrence of co-precipitation of biologically labile biomass nitrogen compounds with humic polymers during the alkaline extraction procedure involved in the humic-fulvic fractionation.

How are soil use and management reflected by soil organic matter characteristics: a spectroscopic approach

“…An additional explanation could be the enrichment of N-rich microbial metabolites in the silt and clay fractions. Such N-rich metabolites are known to be rapidly included in soil humic fractions (Knowles & Barro, 1981). In the Ultuna long-term experiment, microbial biomass was greater in silt-and clay-sized fractions than in the fine-sand fraction.…”

Hydrolyzable Organic Forms of Nitrogen in some Rice Soil Profiles as Affected by Organic Matter Application

“…Aside from deeper soil horizon, N in soil is mainly organic in nature, hence normally only a small portion of total N is present in an inorganic form (4,24,30,32). The organic forms of soil N occur in various stages of humification and decomposition, and are closely related to the microbial activity (2,5,17,18,25,(33)(34)(35). This in turn contributes to the net release of N from the organic reserve as mineral N (l0, 13,16,19,20).…”