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Microbial biomass and microbial C:N ratio in bulk soil and buried bags for evaluating in situ net N mineralization in agricultural soils
Author(s) -
Friedel Jürgen K.,
Gabel Doris
Publication year - 2001
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200112)164:6<673::aid-jpln673>3.0.co;2-r
Subject(s) - mineralization (soil science) , soil water , plough , incubation , agronomy , biomass (ecology) , environmental science , grassland , chemistry , environmental chemistry , soil science , biology , biochemistry
The in situ net nitrogen mineralization (N net ) was estimated in five agricultural soils under different durations of organic farming by incubating soil samples in buried bags. Simultaneously, soil microbial C and N was determined in buried bags and in bulk soil under winter wheat and after harvest. The aim was to check for variations in soil microbial biomass contents and microbial C:N ratios during the incubation period, and their importance for N net rates. Microbial C and N contents were highest in soils that had been organically farmed for 41 years, whereas N net rates were highest in a short‐term organically managed soil that had been under grassland use until 36 years ago. The mean coefficient of variation in the bulk soil for microbial C estimates ranged from 5 to 12 %. Microbial N contents were similar inside buried bags and in the bulk soil at the end of the incubation periods. Under winter wheat during the incubation period until harvest, microbial C contents and microbial C:N ratios (in 10—27 cm depth only) decreased more strongly inside buried bags than in the bulk soil. Following harvest of winter wheat and ploughing, microbial biomass increased while in situ N net decreased, presumably due to N immobilization. The N net rates were not correlated with microbial N contents or changes in microbial N contents inside buried bags. At the end of the vegetation period of winter wheat, N net rates were negatively correlated with microbial C:N ratios. Because these ratios concurrently decreased more inside buried bags than in the bulk soil, the N net estimates of the buried bag method may differ from the N net rates in the bulk soil at that time.