|Pikul Jr, Joseph|
Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2005
Publication Date: 12/1/2005
Citation: Wienhold, B.J., Pikul Jr, J.L., Liebig, M.A., Mikha, M.M., Varvel, G.E., Andrews, S.S., Doran, J.W. 2005. Cropping system effects on soil quality in the great plains: synthesis from a regional project. Renewable Agriculture and Food System 21:49-59. Interpretive Summary: Soils provide nutrients and physical support for plants, store and purify water, and effect air quality. How soils are managed determines how well soils perform their functions. A regional study was conducted to compare soil function using common management practices to those when alternative practices are used. This comparison was accomplished using two new assessment tools. These tools aid in interpreting measured physical, chemical, and biological soil properties to determine if management induced changes are improving or degrading soil functions. Both tools were effective in detecting changes in soil properties that effected crop production and environmental quality. From this study we conclude that soil properties need to be measured over several years to meaningfully compare among management practices; that the assessment tools compared will be useful for users that do not have extensive education or experience in interpreting soils data; and that management systems with reduced tillage, reduced periods of fallow, and diverse crop rotations improve soil function throughout the Great Plains.
Technical Abstract: Soils perform a number of essential functions affecting management goals. Soil functions were assessed by measuring physical, chemical, and biological properties in a regional assessment of conventional (CON) and alternative (ALT) management practices at eight sites within the Great Plains. The results, reported in accompanying papers provide excellent data for assessing how management practices collectively affect agronomic and environmental soil functions that benefit both farmers and society. Our objective was to use the regional data as input for two new assessment tools to evaluate their potential and sensitivity for detecting differences (aggradation or degradation) in management systems. The Soil Management Assessment Framework (SMAF) and the AgroEcosystem Performance Assessment Tool (AEPAT) were used to score individual soil properties at each location relative to expected conditions based on inherent soil forming factors and to compute index values that provide an overall assessment of the agronomic and environmental impact of the CON and ALT practices. SMAF index values were positively correlated with grain yield (an agronomic function) and total organic matter (an agronomic and environmental function). They were negatively correlated with soil nitrate concentration at harvest (an indicator of environmental function). There was general agreement between the two assessment tools when used to compare management practices. Users can measure a small number of soil properties and use one of these tools to easily assess the effectiveness of soil management practices. Higher scores in either tool identify more environmentally and agronomically sustainable management. Temporal variability in measured indicators makes dynamic assessments of management practices essential. Water-filled pore space, aggregate stability, particulate organic matter, and microbial biomass were sensitive to management and should be included in studies aimed at improving soil management. Reductions in both tillage and fallow combined with crop rotation has resulted in improved soil function (e.g. nutrient cycling, organic C content, and productivity) throughout the Great Plains.