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This study examined the residual effects of 4 or 5 years of previous cropping regimes, which included grasses, legumes and fallow, each with or without annual nitrogen (N) fertilization, at three locations in Alaska. At two locations, some previous management practices, especially fallow and in some cases N fertilization, resulted in increased yields of subsequent cereal crops. These effects disappeared by the second year of the study. Significant effects were not found at a third site. Soil bulk density, organic carbon (C) and N, and microbial biomass C and N were not affected by previous treatments. Soil wet aggregate stability, pH, and mineralizable C and N were significantly affected in at least one location by previous cropping or N fertilization. Effects of previous management had disappeared or were diminished by the autumn of the year following cessation of the treatment. These results indicate that effects due to past cropping history may be short lived in subarctic agricultural soils. [ABSTRACT FROM AUTHOR]

Forage crops and soil attributes were evaluated for 4 years at three sites in Alaska. Annual herbage yields usually exceeded 5 Mg ha[sup -1] on neutral soils at Fairbanks (64°52' W) and on moderately acidic soils at Point MacKenzie (61°24' N, 150°3' W). Strongly acidic, droughty soils at Delta Junction (63°55' N, 145°20' W) produced low yields for all crops. Soil pH decreased significantly over 4 years under N-fertilized grasses at Delta Junction and under alfalfa and N-fertilized barley at Fairbanks. Soil organic C and N and microbial biomass C showed no differences among treatments at the end of the study. Wet aggregate stability did not vary significantly among crops but was lower for fallow. The results of this study indicated a high potential for use of perennial forage legumes at some locations in Alaska. The lack of large differences in most soil parameters indicates slow responsiveness to management by some commonly used soilquality indicators under subarctic conditions. [ABSTRACT FROM AUTHOR]