|Carpenter Boggs, Lynne|
|Pikul Jr, Joseph|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/4/1999
Publication Date: N/A
Technical Abstract: Continuous corn (Zea mays) (CC), corn-soybean (Glycine max) (CS), and corn-soybean-wheat/alfalfa (Medicago sativa)-alfalfa (CSWA) crop rotations have been maintained in 0N (no additional N), LN (114 kg N ha**-1), and HN (181 kg N ha**-1) treatments at Brookings, SD since 1990. Total microbial biomass and activity in spring soil samples were not significantly affected by rotation. However, microbial biomass and activity were highest in 0N and lowest in HN plots. During 189 d in a soil temperature-mimicking incubator, soil from CSWA plots mineralized 216 kg N ha**-1, 37% more N than CS and 51% more N than CC. Soils in 0N treatment mineralized 10% more N than soils that had received mineral fertilizers in the previous eight years. Spring nitrate content was generally a good predictor of N mineralization, but underestimated mineralization potential in 0N soils. Rotation with alfalfa had the expected effect of increasing mineralized N, but did not significantly affect general microbial parameters. Mineral N fertilization decreased and/or 0N treatment increased microbial parameters and N mineralization in all rotations.