Submitted to: Minnesota Academy of Science Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/1996
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Nitrogen (N) is the major limiting factor in most crop production. Microorganisms in soil can produce nitrate-N (NO3-N) and this capacity is affected by certain soil and climatic conditions. Accurate prediction of NO3-N production in soil would improve N use efficiency and decrease the amount of excess N-fertilizer added to crops, thus minimizing groundwater pollution due to excess N-fertilizer and reducing costs for crop producers The Cordes model predicts natural soil NO3-N formation by use of air temperature, soil pH, soil clay content, soil organic matter, and rainfall data. It accurately predicts NO3-N formation in many cases, but under very wet conditions, agreement between observed and predicted concentrations of NO3-N are much poorer. In these cases, infiltrated rainfall leaches a portion of the NO3-N into the subsoil with the excess rainfall. A leaching function which partitioned rainfall between infiltrated water and surface runoff water was incorporated in the Cordes model. Incorporation of a leaching function produced closer agreement between predicted and observed field results. Field values of the change in soil NO3-N were obtained from five farms in West Central and Southwestern Minnesota. Mean values of observed changes in NO3-N ranged from 0.37 to 5.83 ug g**-1; mean predicted changes ranged from 2.21 to 7.43 ug g**-1 without leaching and from 2.02 to 6.43 ug g**-1 with leaching. The model predicts leaching of about 10 to 15% of the NO3-N produced. The revised model produces a more accurate prediction of NO3-N formation under a wider range of climatic conditions.