Crop Yield and Soil Characteristics Following Various Cropping Regimes in Alaska

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.