Extractability of microbial 14C and 15N following addition of variable rates of labelled glucose and (NH4)2SO4 to soil
Extractability of microbial 14C and 15N following addition of variable rates of labelled glucose and (NH4)2SO4 to soil
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DOI：
10.1016/0038-0717(90)90019-v
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发表时间：
1990
影响因子：
9.7
通讯作者：
E. Bremer;C. Kessel
中科院分区：
文献类型：
--
作者：
E. Bremer;C. Kessel
The objective of this study was to investigate the effect of variable rates of substrate addition and length of incubation period onin situestimates of the proportion of microbial C and N released by a chloroform-fumigation-extraction method. A Bradwell silty loam soil containingca340 μg microbial C g−1soil was amended with [14C(U)]glucose and [15N](NH4):SO4at 30 and 2. 300 and 2, and 300 and 20μg of C and N. respectively, g−1soil. The following measurements were taken at 0.25, 0.5. 1. 3 and 7 days after the addition of substrates: respired14C, mineral15N, total15N and increase in extractable14C and15N upon fumigation.14C-efficiency, defined as the proportion of14C in the microbial biomass relative to the total amount of14C removed from the soil solution, was >70% in all treatments at 0.25 and 0.5 days and in the treatment receiving the lowest rate of glucose at all sampling times. The proportion of microbial14released by fumigation-extraction was >40% when the efficiency was >70%. but was 34% when the efficiency was lower. In the treatment receiving the low rate of glucose microbial N accounted forca50% of added15N, of which >40% was released by fumigation-extraction; in the treatments receiving the high rate of glucose microbial N accounted for an average of 81% of added15N, of with only 24% was released by fumigation-extraction at 3 and 7 days after the addition of substrates. Based on these observations, it was concluded that at low rates of glucose addition microbial14C and15N remained present among cytoplasmic constituents and little if any was utilized in biosynthesis; sufficient glucose to stimulate microbiul growth and a sufficient period of incubation would be required to obtain reliable estimates of the proportion of microbial C and N released upon fumigation-extraction.
