LLWR techniques for quantifying potential soil compaction consequences of crop

Authors: Benjamin, Joseph; Karlen, Douglas

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2013
Publication Date: 6/1/2014
Publication URL: https://handle.nal.usda.gov/10113/59348
Citation: Benjamin, J.G., Karlen, D.L. 2014. LLWR techniques for quantifying potential soil compaction consequences of crop. BioEnergy Research. 7:468-480.

Interpretive Summary: Harvesting crop residues for bioenergy or bio-product production may decrease soil organic matter, resulting in the degradation of soil physical properties and ultimately soil productivity. The Least Limiting Water Range can be used to evaluate improvement or degradation of soil physical properties in response to soil organic matter changes, but its use has generally been hampered by the extensive amount of data needed to identify the limiting factors for crop production. Our objective was to evaluate five methods to predict effects of changing soil organic matter on soil water holding capacity and two methods to determine effects of changing soil organic matter on soil strength. Predictions of water content as well as the soil strength – water content – bulk density relationship using the methods were compared with field data from two tillage experiments near Akron, CO that had a range of soil organic matter levels. Equations previously developed by da Silva and Kay gave the best estimates of the Least Limiting Water Range for the methods we evaluated. These equations were then used to illustrate Least Limiting Water Range changes in response to different soil and crop management practices on a Duroc loam near Sidney, NE. The results showed that soil physical properties were degraded by the loss of soil organic matter due to tillage and, possibly, soil erosion. Therefore, we recommend that crop residue removal rates be limited to rates that maintain or increase soil organic matter content to ensure soil physical conditions are not degraded.

Technical Abstract: Harvesting crop residues for bioenergy or bio-product production may decrease soil organic matter (SOM), resulting in the degradation of soil physical properties and ultimately soil productivity. Using the Least Limiting Water Range (LLWR) to evaluate improvement or degradation of soil physical properties in response to SOM changes has generally been hampered by the extensive amount of data needed to parameterize limiting factor models for crop production. Our objective was to evaluate five pedotransfer functions to determine their effectiveness in predicting soil water holding capacity in response to different SOM levels. Similarly, two other pedotransfer functions were evaluated to determine effects of SOM on cone index values. Predictions of field capacity and wilting point water content as well as the cone index – water content – bulk density relationship of soil strength using the pedotransfer functions were compared with field data from two tillage experiments near Akron, CO that had a range of SOM concentrations. Equations previously developed by da Silva and Kay gave the best estimates of LLWR for the pedotransfer functions we evaluated. These equations were then used to illustrate LLWR changes in response to different soil and crop management practices on a Duroc loam near Sidney, NE. The results showed that soil physical properties were degraded by the loss of SOM due to tillage and, possibly, soil erosion. Therefore, we recommend that crop residue removal rates be limited to rates that maintain or increase SOM content to ensure soil physical conditions are not degraded.