Microbial biomass as a fraction of potentially mineralizable nitrogen in soils from long-term field experiments
1988 (English)In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 20, no 4, 447-452 p.Article in journal (Refereed) Published
Aerobic long-term incubations (40-wk) were employed to measure the potentially mineralizable nitrogen (N0) in five 30-yr old cropping systems. The cropping systems consisted of: (1) bare fallow; (2) cropping with no additions; (3) cropping with 80 kg N ha-1 y-1 as Ca(NO3)2; (4) cropping with 80 kg N ha-1 yr-1 as Ca(NO3)2 plus 1800kg C ha-1 yr-1 as straw; and (5) cropping with 80 kg N ha-1 yr-1 plus 1800 kg C ha-1 yr-1 as farmyard manure. The amounts of N mineralized during the 40-wk incubations were between 93 and 168 μg g-1 (302-543 kg N ha-1 down to 25cm depth) with the lowest value for the fallow and the highest for the farmyard manure treatment. Microbial biomass-C and -N were measured on four occasions during the incubations. The biomass-C showed a rapid decrease to week 4 (to 36% of the initial mass), a slower decrease to week 9 (to 23% of initial mass) and a very slow decline to the final determination at the end of the incubation (to 8% of initial mass). The biomass-N displayed a similar pattern. Two related models were employed to describe the kinetics of N-mineralization during incubation: (1) a two-component first-order; and (2) a simplified special case of the two-component model. In all cases except the straw-amended soil, the simplified two-component model offered the best description of the curves of accumulated mineral-N. The available fraction, Na, of soil organic-N had mineralization rate constants similar to those for mineralization of microbial biomass.
Place, publisher, year, edition, pages
Elsevier, 1988. Vol. 20, no 4, 447-452 p.
IdentifiersURN: urn:nbn:se:oru:diva-52232DOI: 10.1016/0038-0717(88)90056-9ISI: A1988Q193800005ScopusID: 2-s2.0-45549117613OAI: oai:DiVA.org:oru-52232DiVA: diva2:971155