|Exner, D - IOWA STATE UNIVERSITY|
|Delate, K - IOWA STATE UNIVERSITY|
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 2003
Publication Date: November 6, 2003
Citation: EXNER, D.N., DELATE, K., KARLEN, D.L. SOIL FERTILITY PARADIGMS -- CATION RATIO AND SUFFICIENCY -- COMPARED ON-FARM AND ON-STATION. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. 2003. CD-ROM. MADISON, WI. Technical Abstract: The cation ratio (CR) and sufficiency level of available nutrients (SLAN) are very different approaches for managing soil fertility. Most agronomists consider the evidence, including work by Von Liebig, Mitscherlich, Sprengel, and Macy, to favor SLAN. A strongly held minority opinion based on Bear, Albrecht, and others holds that crops grow best when the proportion of nutrients on the soil cation exchange conforms to a preferred ratio (CR). With no dialog between these viewpoints, farmer decisions with important economic consequences may be ill-informed. We conducted side-by-side comparisons to evaluate the short-term agronomic and economic outcomes of the two approaches. For three years in fixed plots on two university and six private farms, we compared CR and SLAN. Amendments were based on the two interpretations of annual soil tests. Grain yield and quality, leaf and soil mineral analysis, aggregate stability, particulate organic matter, weed biomass, and costs were evaluated. Few clear agronomic trends emerged using univariate and principal components analysis, suggesting that on similar highly fertile Mollisols, short-term differences in yield, soil quality indicators, and weed pressure between the CR and SLAN approaches may be minimal. The most striking treatment difference was in net profit; input costs averaged $10.42 U.S. per acre ($25.74/ha) more for CR than SLAN.