Submitted to: International Journal on Subsurface Sensing Technologies & Applications
Publication Type: Proceedings
Publication Acceptance Date: 6/2/2004
Publication Date: 6/21/2004
Citation: Gish, T.J., Daughtry, C.S.T., Walthall, C.L., Kung. K. 2004. Qualifying impact of hydrology on corn grain yield using ground-penetrating radar. In: Proceedings 10th International Conference on Ground-penetrating Radar, June 21-24, 2004, Delft, The Netherlands. 2:493-496. Interpretive Summary: Understanding factors controlling within field crop production variability is essential for the development of environmentally friendly and economically viable agricultural production systems. Hydrology plays a leading role in crop production and soil ecology as soil moisture influences yield and the behavior of agricultural chemicals. Although surface topography and subsurface soil layering have an impact on the temporal and spatial nature of soil moisture, its subsequent impact on yield patterns has not been quantified. Quantifying the impact of hydrology on corn grain yield was investigated at the Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) program using primarily ground-penetrating radar (GPR). Results show that discrete subsurface water flow pathways exist under the soil surface. When these GPR-identified flow pathways come within 2 m of the soil surface they have a dramatic impact on crop growth and yield. For example, during growing seasons with below or average rainfall, these flow pathways have a beneficial impact on yield. However, when rainfall is abundant, soil moisture conditions are too wet and yields near these GPR-identified subsurface flow pathways decline. This research indicates that GPR may be an effective tool for quantifying the impact of hydrology on crop production.
Technical Abstract: Understanding hydrologic processes is fundamental for characterizing agricultural chemical behavior and crop production at the field and watershed scales. Unfortunately, crop production patterns and hydrologic processes exhibit significant spatial and temporal variability. The concept of soil moisture response zones has been proposed and found to be an effective means for identifying areas within a field that are hydrologically similar. Soil moisture response zones were determined using normalized spatial yield patterns from divergent climatic conditions on a small watershed at the USDA-ARS Agricultural Research Center, Beltsville, Maryland USA. Subsurface hydrology was determined by identifying subsurface convergent flow pathway locations using ground-penetrating radar (GPR), digital elevation maps (DEM) and a GIS. Frequent volumetric soil moisture measurements confirmed the existence of discrete preferential funnel flow processes occurring near the GPR-identified preferential flow pathways. Although the spatial variability of corn (Zea mays L.) grain yield generated coefficients of variation > 114% during a drought, yield were strongly effected by their proximity to GPR-identified subsurface flow pathways. Corn grain yields and the soil moisture response index decreased as the horizontal distance from the GPR-identified subsurface flow pathways increased during a drought. During a growing season where precipitation was abundant, this quantitative relationship was reversed. This research suggests that GPR is an effective tool for quantifying the impact hydrology on crop production.