Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/25/2013
Publication Date: 3/4/2013
Publication URL: http://handle.nal.usda.gov/10113/56975
Citation: Benjamin, J.G., Nielsen, D.C., Vigil, M.F., Mikha, M.M., Calderon, F.J. 2013. A comparison of two models to evaluate soil physical property effects on corn (Zea mays, L.)root growth. Agronomy Journal. 105:713-720. Interpretive Summary: Models are used to integrate the complexities of the soil-plant-atmosphere continuum. Soil physical properties interact with the plant through the effects on the plant root system. Two models were compared in this study: a model currently incorporated in several complex soil-plant-atmosphere models (here called the Jones model), and a new model called the Least Limiting Water Range (LLWR). A wide range of soil conditions were created with a tillage-irrigation-crop rotation field study at the Central Great Plains Research Station at Akron, Colorado. Bulk density and water content measurements were made during the growing season and root samples from a corn crop were made at three time intervals. Using linear regressions of root surface area density with the cumulative root growth suitability showed the criteria for soil physical limitations identified by the LLWR model resulted in positive, linear relationships between the variables at nearly all times and depths. Regressions using the Jones criteria often showed a negative correlation between soil physical condition and root surface area, and the correlation coefficients were much smaller. It is recommended that soil physical restrictions as identified by the LLWR model be incorporated in larger, more complex models to better simulate the interaction between soil conditions and plant growth.
Technical Abstract: There is a need to understand the complex interactions among soil physical properties, root growth and development, and plant response to changing physical conditions to provide optimum soil management for crop production. Two models of evaluating soil physical condition effects on root growth were compared. The first model, herein called the Jones model, is a submodel for root growth limitations used by several complex soil-plant-atmosphere models. The second model uses soil physical limitations as identified by the Least Limiting Water Range (LLWR). Root surface area density (Rsa) and bulk density was determined at the V6, V12, and R1 growth stages of corn. Water contents through the growing season were determined twice per week with a neutron probe. The cumulative predicted relative root growth suitability (PRGS) was determined using soil physical limitations to root growth defined by each model. Regressions of the Rsa with PRGS using the LLWR criteria for soil physical limitations nearly always resulted in a linear, positive slope, indicating more root surface area with better soil conditions. Regressions of the Rsa with PRGS using the Jones criteria for soil physical limitations nearly always resulted in a linear, negative slope, indicating less root surface area with better soil conditions. Linking restrictive soil criteria as identified by the LLWR model to a more comprehensive model of total plant and root growth and comparing root response to soil conditions using the Jones criteria for restrictive conditions may help in our understanding of the soil-plant-atmosphere continuum.