Abstract
Studies were conducted to evaluate the relationships among different active N pools of organic matter in soils at two long-term crop** systems in Iowa. Results indicated that multi-crop** systems, particularly meadow-based systems, enhanced bioactivities of soils. Mono-crop** 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).
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Received: 18 October 1999
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Deng, S., Moore, J. & Tabatabai, M. Characterization of active nitrogen pools in soils under different crop** systems. Biol Fertil Soils 32, 302–309 (2000). https://doi.org/10.1007/s003740000252
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DOI: https://doi.org/10.1007/s003740000252