are many reasons for this, among them the development of effective fertilizers and pesticides, government poli-In the USA, the corn (Zea mays L.)-soybean [Glycine max (L.) cies, and favorable economics. Interest in developingMerr.] rotation depends on high levels of external inputs. Few research data exist comparing conventional production practices with practices alternatives to the present agricultural system has arisen involving reduced external inputs and expanded rotations. Two trials from a number of environmental, economic, and social initiated in 1989 near Lamberton, MN, evaluated a 2-yr corn-soybean issues, including heightened concern over water quality, rotation and a 4-yr corn-soybean-oat (Avena sativa L.)/alfalfa (Medincreased reliance on government subsidies, and a conicago sativa L.)-alfalfa rotation under four management strategies. tinued decline in rural populations. The four management strategies were zero (ZI), low (LI), high (HI), Agricultural productivity gains since the 1950s reand organic (OI) inputs. One trial (V1) was on land with a history sulted from the development of farming systems that of no fertilizer and pesticide usage. The other trial (V2) was on land rely heavily on external inputs of energy and chemicals with a history of conventional fertilizer and pesticide usage. From to replace management and on-farm resources (Oberle, 1993 through 1999, average corn yield in the 2-yr HI strategy was 1994). Continuous rotation of corn and soybean cannot 8.96 Mg ha Ϫ1 in V1 and 8.72 Mg ha Ϫ1 in V2. Corn yield in the 4-yr HI strategy was 4% less than in the 2-yr HI strategy in V1, whereas be sustained without substantial additions of fertilizer in V2, the yields were not different. Soybean yield in the 2-yr HI and pesticides (Heichel, 1978; Pimentel et al., 1978). A strategy was 2.90 Mg ha Ϫ1 in V1 and 2.74 Mg ha Ϫ1 in V2. Soybean number of research studies have been conducted comyield in the 4-yr compared with the 2-yr HI strategy was 3% greaterparing conventional corn-soybean production systems in V1 and 6% greater in V2. These results suggest soybean was more with low-input and organic production systems, includresponsive than corn to the expanded rotation length in the HI strating those by Chase and Duffy (1991) and Karlen et al. (1995) in Iowa, Munn et al. (1998) in Ohio, Liebhardt strategy was 9% less in V1 and 7% less in V2 while soybean yield in et al. (1989) in Pennsylvania, Smolik and Dobbs (1991) the 4-yr OI strategy compared with the 2-yr HI strategy was 19% less and Smolik et al. (1995) in South Dakota, and Posner in V1 and 16% less in V2. These results suggest that yield of organically et al. (1995) and Mallory et al. (1998) in Wisconsin. produced soybean was reduced to a greater extent than that of organically produced corn relative to conventional production practices. By egy. Corn yield in the 4-yr OI strategy compared with the 2-yr HIThe economics of organic grain and soybean production comparing yields of the 2-and 4-yr rotations for each management from several stud...

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In spite of concerns, Minnesota‘s dominant cropping system is the corn–soybean rotation using synthetic pesticides and chemically processed fertilizers. Using experimental data from 1990–99, this study compared the profitability of organic versus conventional strategies. Net return (NR) was calculated from actual yields, operations, inputs, prices and organic premiums. Yields and costs were lower for the 4-year organic strategy. With premiums, the 4-year organic strategy had NRs significantly higher than conventional strategies; without premiums, the NRs were statistically equal (P = 0.05). Thus, the 4-year organic strategy was not less profitable nor its NR more variable than the conventional strategies in this study.

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Dyes are often used as tracers of water and solute flow in soil. However, there has been little published research on the effects of flow velocity on the relative movement of dye and wetting fronts. Recently, the FD&C Blue no. 1 dye has been used as a tracer of preferential water flow paths in soils, and has attractive properties suggesting it will be used increasingly in the future. The objective of this study was to characterize the effects of flow velocity on the adsorption characteristics of the FD&C Blue no. 1. We performed a series of laboratory experiments on the characterization of the equilibrium adsorption isotherm as well as the effect of flow velocity on adsorption characteristics of the FD&C Blue no. 1 in three horizons of Verndale sandy loam (coarse‐loamy over sandy, mixed, frigid Udic Argiboroll). Batch equilibration (24 h) measurements resulted in linearized Freundlich distribution coefficients (Kd) of 4.33, 23.95, and 4.59 L kg−1 for the Ap, Bt, and C horizons, respectively. Neither organic C nor clay content differences accounted for the variation between horizons. Leaching experiments with a 1 g L−1 dye solution and repacked soil columns containing either Ap, Bt, or C horizon material showed that the dye was retarded relative to the wetting front, and that the extent of retardation was inversely related to the time period during which dye solution was applied. Therefore, this dye (and perhaps others) should not be used to make inferences about the movement of water or other solutes until the effect of the application rate is evaluated for the flow conditions in the system(s) of interest.