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Alternative cropping systems can improve resource use efficiency, increase corn grain yield, and help in reducing negative impacts on the environment. A 6-yr (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 (Avena sativa L.)]; alfalfa rotation (ROT)-3-yr (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...
A GLEAMS (ver. 2.10) model was calibrated and validated using three years (1990–1992) of field–measured data to simulate tillage effects on nitrate–nitrogen (NO3–N) and herbicide losses with subsurface drain “tile” water beneath a continuous corn production system. The model was calibrated for chisel plow systems using 1991 field data and was validated against field data of two years (1990 and 1992) for chisel plow and three years (1990–1992) for moldboard plow (MB), ridge till (RT), and no–till (NT) systems. The model simulations were made with a single run using data on measured tile flows; nitrate–nitrogen (NO3–N), atrazine, and alachlor losses with tile flows; N–uptake; and other biomass parameters for the period...
Long-term applications of organic or inorganic sources of N to croplands can increase the leaching potential of nitrate–nitrogen (NO3–N) for soils underlain by subsurface drainage “tile” network. A field study was conducted for 6 years (1993–1998) to determine the effects of liquid swine manure and urea ammonium nitrate (UAN) solution fertilizer applications on NO3–N concentrations and NO3–N losses with subsurface drainage water under continuous corn (Zea maize L.) and corn after soybean (Glycine max. L.) production systems. The field data collected at Iowa State University's northeastern research center near Nashua, Iowa, under six N-management treatments and each replicated three times, were analyzed as a randomized...
Increasing global population in the world is putting enormous pressure on available water resources and preservation of water quality. Therefore, sound policies with good incentives are needed to implement water conservation and pollution control practices, especially in areas of the world where major water bodies are already showing signs of degradation. To develop sustainable agricultural production practices, long-term studies were initiated in 1988 at Iowa State University to determine the effects of different tillage, crop rotation, and nutrient (fertilizer and manure) management systems on water use, crop yields, and nitrate–nitrogen (NO3-N) leaching losses to groundwater with the goal of mitigating environmental...
This study was designed to evaluate the improved version of the Root Zone Water Quality Model (RZWQM) using 6 yr (1992–1997) of field-measured data from a field within Walnut Creek watershed located in central Iowa. Measured data included subsurface drainage flows, NO3–N concentrations and loads in subsurface drainage water, and corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields. The dominant soil within this field was Webster (fine-loamy, mixed, superactive, mesic Typic Endoaquolls) and cropping system was corn–soybean rotation. The model was calibrated with 1992 data and was validated with 1993 to 1997 data. Simulations of subsurface drainage flow closely matched observed data showing model efficiency...
Adoption of precision agriculture requires delineation of the stable management zones so that site-specific management practices can be applied to improve crop productivity and environmental quality. A quantitative approach was developed to delineate the zones by using the map overlay capability of Geographic Information System (GIS) for the soil type, topography and crop yield data layers based on field data from 1996 through 1999. The study was conducted on a 22-ha tile drained corn (Zea mays L.)-soybean (Glycine max L.) rotation field, located near Story City, Iowa. The integration of data layers showed that low yield zones were consistent from year to year and were affected by the interaction of soil type and...