Nutrient considerations for diversified cropping systems in the northern Great Plains

The impacts of recent changes in cropping systems in the northern Great Plains on nutrient dynamics are described in this review paper. Cropping intensity and diversity are increasing in the Great Plains because reduced tillage systems have improved water conservation and, subsequently, crop yields. Higher annualized crop yields increase nutrient removal which must be balanced by increased nutrient inputs to ensure optimal crop yield and quality. while avoiding soil depletion. Furthermore, diversification of crops alters the pattern and degree of nutrient removal and influences microbiological activity and soil quality. Although cropping intensification and diversification will influence most plant nutrients, N and P are the nutrients most commonly deficient for crop production in the Great Plains and most likely to be affected by management practices. Cropping intensification increases crop residue return to the soil, which in turn increases the soil organic C pool. This can lead to higher soil organic matter levels and a greater potential for nutrient cycling, an effect that will increase with time. Cropping systems that include legumes have the potential for contributing N to following crops and may moderate NO3 levels in the soil to avoid potential for NO3 leaching. Phosphorus availability may be influenced by depletion or accumulation of P, based on past cropping and fertilizer management. In addition, preceding crop may influence P availability through residue effects and impacts on vesicular-arbus-cular mycorrhizae activity. Synchrony of nutrient supply with crop demand is essential in order to ensure optimum crop yield and quality while avoiding negative environmental impacts.