Characterization of active nitrogen pools in soils under different cropping systems |
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| Authors: | S P Deng J M Moore M A Tabatabai |
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| Institution: | (1) Department of Agronomy, Iowa State University, Ames, IA 50011–1010, USA e-mail: malit@iastate.edu Fax: +1-515-2943163, US |
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| Abstract: | Studies were conducted to evaluate the relationships among different active N pools of organic matter in soils at two long-term
cropping systems in Iowa. Results indicated that multi-cropping systems, particularly meadow-based systems, enhanced bioactivities
of soils. Mono-cropping systems, particularly soybean, reduced soil microbial biomass and enzyme activities. The mineralizable
N pool (potential N mineralization;N
o) was more sensitive to changes in the size of the microbial biomass N (Nmic) than to changes in organic N. One unit change in organic N did not lead to substantial changes in N
o, but 1 unit change in Nmic resulted in three or more units change in N
o. The active N pools and turnover rate were more sensitive to changes in organic C than to changes in microbial biomass C
(Cmic). A unit change in organic C resulted in 10.6 units change in N
o, but a unit change in Cmic resulted in only 0.8 unit change in N
o. Cmic or Nmic are better indexes than organic C or N for the estimation of N
o or N availability, because biomass values are more highly correlated with cumulative N mineralized during 24 weeks of incubation,
with r values ranging from 0.57 (P<0.001) to 0.88 (P<0.001).
Received: 18 October 1999 |
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| Keywords: | Biomass carbon Biomass nitrogen Cropping systems Nitrogen mineralization constants Active nitrogen pools |
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