Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2007
Publication Date: 7/15/2007
Citation: Ahuja, L.R., Hatfield, J.L. 2007. Integrating Soil and Crop Research with System Models in the Midwest USA: Purpose and Overview of the Special Issue. Geoderma. Vol.140;3. pp 217-222. July 15, 2007. doi:10.1016/j.geoderma.2007.04.006. Interpretive Summary: The overall goal of this Special Issue was to illustrate the advantages of integrating field research data with whole-system models for better understanding, quantifying, and extending the experimental results for the effects of a variety of management practices on crop production and quality of drainage water. This is accomplished through a case study and analysis of a long-term database from the Northeast Research Center of the Iowa State University near Nashua, Iowa, USA, involving a series of focused and inter-related papers for different management proactices. This subject addresses the important stated objective of Geoderma: "For many years, Geoderma has helped to stimulate wide interdisciplinary cooperation and understanding among workers in the different fields of soil science by bringing together papers from the entire field of soil research rather than emphasizing any one sub-disciline. The Journal welcomes interdisciplinary work preferably focusing on occurrence and dynamic characterization in space and time of soils in the field."
Technical Abstract: The Nashua experimental site was one of the USDA Management Systems Evaluations (MSEA) sites in 1990s to evaluate agricultural systems and management effects on water quality and crop production in the Midwestern U.S. This site has been used to evaluate several different agricultural management practices and treatments. The experimental site consists of 36 one-acre plots established in 1977. Tile drains were installed on the site in 1979. The site has gone through three experimental periods from 1977-1993, from 1993-1998, and from 1998-2002. Intensive data collection was initiated in 1990. On the other hand, Nashua experimental site also has a complex landscape topography, which causes a highly variable tile flow from plot to plot. Each plot has a buffer tile line at its upper and lower boundaries (open ditch tiles), and one tile line in the middle (trenchless tile) to measure average tile flow out of the plot. However, the highly variable tile flow among plots indicates that the buffer tile lines may not completely isolate the lateral groundwater flow at the boundaries, and the flows to the middle tile and buffer tiles are not equal. This lateral groundwater flow is very difficult characterize and is thus a big unknown that may affect the results of simulations with a one-dimensional model. In addition, there was also a spatial variability in soil properties and the missing daily weather data were obtained from off-site measurements in nearby locations, both of which add to the complexity in model application. From 1977-1992, the main focus of the study was on tillage practices (moldboard plow, chisel plow, ridge-till, and no-till) and crop rotations (continuous corn, corn-soybean, soybean-corn). Only crop yield was measured from 1977 to 1989. Detailed data were collected in 1990-1993, including tile flow, nitrate and pesticide in tile flow, residual soil N content, biomass, yield, and N uptake. Pesticide (cyanazine, alachlor, atrazine, metribuzin) were also measured in soil and tile flow for certain periods of time, but not analyzed for this issue. From 1993-1998, the main focus of the study was on N management, which included options of liquid swine manure, differing N application rates of commercial fertilizer, and determination of rates based on late spring N test. Tillage was reduced from four to two practices (Chisel plow and no-till). Two pesticide application methods were studied (banding and broadcast). Data collection included tile flow, runoff, nitrate and pesticides (atrazine and metolachlor) in tile flow, nitrate and pesticides in soil, N uptake, yield, and biomass. From 1999-2003, the main focus of the study was on manure application rate, timing, and method. Manure application rates were based on N or P needs for corn and soybean. Application methods included incorporation, injection, and localized compaction and doming application. Manure was applied either in the fall or spring. Chisel plow and no-till management practices were continued. Crop rotations were continuous corn and corn-soybean. Each corn season received manure or/and UAN (Urea Ammonium Nitrate). Experimental measurements included tile flow, nitrate in tile flow, N and P in soil, N uptake, yield, and biomass. The results of these studies have been reported in many publications (Karlen et al., 1991, 1998, 2004; Weed et al., 1995, 1996; Kanwar et al., 1997, 1999, 2005; Bjorneberg et al., 1998; Singh and Kanwar, 1995a, 1995b; Singh et al., 1996; Azevedeo et al., 1997a, 1997b; Kumar et al., 1998a, 1998b, 1999, Bakhsh and Kanwar, 2001, 2004, 2005; Bakhsh et al., 1999, 2000, 2002, 2005). The publications senior-authored by Singh, Azevedeo, Kumar, and Bakhsh involved the use of models. However, these modeling studies used partial data (2-3 years in each paper) for selected treatments, plots, years, and outputs. On the other hand, the studies rep