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CROPPING SYSTEMS

Agronomic and Economic Performance Characteristics of Conventional and Low-External-Input Cropping Systems in the Central Corn Belt

^a Dep. of Agronomy, Agronomy Hall, Iowa State Univ., Ames, IA, 50011
^b Dep. Hortofruticultura, Botánica y Jardinería, Univ. de Lleida, Av. Alcalde Rovira Roure 191, 25198 Lleida, Spain
^c Iowa State University Extension, 720 7th Avenue SW, Tripoli, IA, 50676
^d Dep. of Land Resources and Environmental Sci., Leon Johnson Hall, Montana State Univ., Bozeman, MT, 59717
^e USDA-ARS Invasive Weed Management Unit, 1102 S. Goodwin Ave., Urbana, IL, 61801
^f Dep. of Statistics, Snedecor Hall, Iowa State Univ., Ames, IA, 50011. Funding for this work was provided by the USDA National Research Initiative (Projects 2002-35320-12175 and 2006-35320-16548), the Leopold Center for Sustainable Agriculture (Project 2004-E6), and the Iowa State University Agronomy Endowment

^* Corresponding author (mliebman{at}iastate.edu).

We conducted a 9-ha field experiment near Boone, IA, to test the hypothesis that yield, weed suppression, and profit characteristics of low-external-input (LEI) cropping systems can match or exceed those of conventional systems. Over a 4-yr period, we compared a conventionally managed 2-yr rotation system {corn (Zea mays L.)/soybean [Glycine max (L.) Merr.]} with two LEI systems: a 3-yr corn/soybean/small grain + red clover (Trifolium pratense L.) rotation, and a 4-yr corn/soybean/small grain + alfalfa (Medicago sativa L.)/alfalfa rotation. Synthetic N fertilizer use was 59 and 74% lower in the 3- and 4-yr systems, respectively, than in the 2-yr system; similarly, herbicide use was reduced 76 and 82% in the 3- and 4-yr systems. Corn and soybean yields were as high or higher in the LEI systems as in the conventional system, and weed biomass in corn and soybean was low (4.2 g m^–2) in all systems. Experimentally supplemented giant foxtail (Setaria faberi Herrm.) seed densities in the surface 20 cm of soil declined in all systems; supplemented velvetleaf (Abutilon theophrasti Medik.) seed densities declined in the 2- and 4-yr systems and remained unchanged in the 3-yr system. Without subsidy payments, net returns were highest for the 4-yr system ($540 ha^–1 yr^–1), lowest for the 3-yr system ($475 ha^–1 yr^–1), and intermediate for the 2-yr system ($504 ha^–1 yr^–1). With subsidies, differences among systems in net returns were smaller, as subsidies favored the 2-yr system, but rank order of the systems was maintained.

Abbreviations: LEI, low-external-input

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Received for publication June 22, 2007.

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