HYDROLOGIC AND ENVIRONMENTAL IMPACTS OF CONSERVATION PRACTICES IN OKLAHOMA AGRICULTURAL WATERSHEDS
Location: Great Plains Agroclimate and Natural Resources Research Unit
Title: Application of DRAINMOD-Ks-STMAX to predict deep chiseling effects on a drained southern alluvial soil
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 2007
Publication Date: February 1, 2008
Citation: Moriasi, D.N., Fouss, J.L., Hall, S.G., Kornecki, T.S. 2008. Application of DRAINMOD-Ks-STMAX to predict deep chiseling effects on a drained southern alluvial soil. Applied Engineering in Agriculture. 24(3):1-10.
Interpretive Summary: Tillage operations such as deep chiseling can increase infiltration and therefore reduce soil erosion, potentially enhancing growth by reducing excess water in the root zone and reducing nutrient losses through the reduction of runoff to surface waters. In the past, DRAINMOD, a water management model, was not able to simulate the effects of deep chiseling on infiltration and runoff. However, DRAINMOD has been modified in the recent past to incorporate deep chiseling algorithms. The objectives of this study were 1) to test the ability of the modified model to predict the impact of deep chiseling on surface and near surface hydrology and 2) to use the modified model as a tool to determine the frequency and timing of deep chiseling. Based on the model outputs on a southern alluvial soil, deep chiseling increased predicted infiltration by 6% to 9%, increased drainage below the ground surface by 2%, and reduced runoff by 19% to 20%. It was determined from the simulation results that the effects of deep chiseling on hydrology decreased with increasing cumulative rainfall since deep chiseling date. For high rainfall states like Louisiana, with average annual rainfall often exceeding 150 cm, this translates to deep chiseling once every year whereas in drier states deep chiseling can be done once every two to three years depending on the amount of rainfall. It is also recommended that farmers deep chisel just prior to planting time to obtain maximum benefits from deep chiseling. The modified DRAINMOD model has potential to be used as tool to quantify the impacts of deep chiseling on hydrology. In addition, model results can be used by extension agents and researchers to advise farmers on the frequency and timing of deep chiseling in order to reap maximum benefits.
Deep chiseling in heavy soils can help increase infiltration and hence reduce erosion, potentially enhancing growth by reducing excess water in the root zone and reducing nutrient losses through the reduction of runoff to surface waters. This study was conducted to test the use of DRAINMOD-Ks-STMAX, a modified form of the water management model, DRAINMOD, 1) to predict the effects of deep chiseling on hydrology for a sub-surface drained plot and 2) as a tool to determine the frequency and timing of deep chiseling. Data from a sub-surface drained plot at Ben Hur Research site near Baton Rouge, LA, were used. Simulation results indicated that deep chiseling a Commerce silt loam, a southern alluvial soil, increased cumulative infiltration (CI) and cumulative sub-surface drainage (CSD) by 9.4% and 2.1%, respectively, and reduced cumulative surface runoff (CRO) by19.7% between September 28, 1995 and November 21, 1996. Between November 22, 1996 and November 22, 1997, it increased CI and CSD by 5.7% and 10.8%, respectively, and reduced CRO by 19.2%. Vertical saturated hydraulic conductivity (Ks) had decreased by 99%, from a maximum initial value immediately after deep chiseling, by the time 150 cm of rain had fallen (approximately 12 months) since deep chiseling. For high rainfall states like Louisiana, with average annual rainfall often exceeding 150 cm, this translates to deep chiseling once every year whereas in drier states deep chiseling can be done once every two to three years depending on the amount of rainfall. Depending on the cumulative amount of rainfall during planting, producers can lose 85% or more of the maximum deep chiseling benefits due to reduced Ks. Because of great rainfall variability in Louisiana and other southern states, it is advisable for farmers to deep chisel their fields just prior to the planting season. Results of this plot modeling study indicate that DRAINMOD-Ks-STMAX can be used to simulate the effects of deep chiseling in poorly drained soils with subsurface drainage and as a tool to advise farmers on the frequency and timing of deep chiseling. However, the model needs to be tested on a field-scale, for longer time periods, and under different climatic conditions and soil types before it can be recommended for general application for the purposes listed above.