|Karlen, Douglas - Doug|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2004
Publication Date: 6/3/2005
Citation: Kanwar, R.S., Cruse, R., Ghaffarzadeh, M., Bakhsh, A., Karlen, D.L., Bailey, T. 2005. Corn-soybean and alternative cropping systems effects on NO3-N leaching losses in subsurface drainage water. Applied Engineering in Agriculture. 21(2):181-188. Interpretive Summary: Continuous corn or a two-year corn/soybean rotation have become the dominant Midwestern cropping systems, primarily because of economics and government programs, but from an environmental viewpoint these systems may not be the best. Our six-year study showed that non-traditional, narrow strip intercropping of corn, soybean, and oat or an extended rotation with three years of alfalfa followed by corn, soybean and oat significantly reduced the flow weighted average nitrate nitrogen concentration in the subsurface drainage water compared to the two-year corn-soybean rotation. Strip-intercropping also increased corn grain yields by five percent and reduced nitrate nitrogen leaching losses by six percent. The results demonstrate that diversifying crop rotations could reduce nitrate nitrogen leaching and perhaps lead to more sustainable farming systems, but markets and new uses for the alfalfa and oat will have to be developed to make the system economically viable. The primary beneficiaries of this research will be public and private nutrient management planners and persons involved with developing new agricultural policies that strive to balance productivity and environmental protection.
Technical Abstract: Alternative cropping systems can improve resource use efficiency, increase corn grain yield, and help in reducing negative impacts on the environment. A 6-year (1993 to 1998) field study was conducted at the Iowa State University's Northeastern Research Center near Nashua, Iowa, to evaluate the effects of non-traditional cropping systems (strip inter cropping (STR)-corn (Zea mays L.)/soybean (Glycine max L.)/oats (Avina sativa L.); alfalfa rotation (ROT)-3-year (1993 to 1995) alfalfa (Medicago sativa L.) followed by corn in 1996, soybean in 1997, and oats in 1998) and traditional cropping system (corn after soybean (CS) and soybean after corn (SC) on the flow weighted average nitrate-nitrogen (NO3-N) concentrations and NO3-N leaching losses with subsurface drainage water. The soils at the research site are loamy with 3 to 4% organic matter and are underlain by a subsurface drainage system. The data collected from four experimental treatments were analyzed as an unbalanced incomplete block design using F-test and T-test among treatments and within treatments, respectively. When averaged across 6 years, non-traditional cropping systems reduced flow weighted average NO3-N concentrations in subsurface drain water significantly (P<0.05) in comparison with traditional cropping system (6.5 vs. 11.2 mg L-1). Similarly the strip inter cropping system increased corn grain yields by 5% (9.03 vs. 8.6 Mg ha-1) and reduced NO3-N leaching losses by 6% (12.6 vs. 13.5 kg-N ha-1) and showed no difference in soybean yields when compared with traditional cropping system. Results of the study indicate that strip inter cropping and alfalfa rotation systems have the potential to reduce NO3-N leaching into the shallow groundwater system and possibly can become one of the better sustainable farming systems in Midwestern agriculture.