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CROPPING SYSTEMS

Organic and Conventional Production Systems in the Wisconsin Integrated Cropping Systems Trials: I. Productivity 1990–2002

^a Dep. of Agronomy, Univ. of Wisconsin, 1575 Linden Dr., Madison, WI 53706
^b AGSTAT, 6394 Grandview Rd., Verona, WI 53593. Major funding provided by the W.K. Kellogg Foundation's Integrated Food and Farming Systems program and federal appropriation from the Agricultural Research Service (ARS) Integrated Farming Systems program

^* Corresponding author (jlposner{at}wisc.edu).

During the last half-century, agriculture in the upper U.S. Midwest has changed from limited-input, integrated grain–livestock systems to primarily high-input specialized livestock or grain systems. This trend has spawned a debate regarding which cropping systems are more sustainable and led to the question: can diverse, low-input cropping systems (organic systems) be as productive as conventional systems? To answer this question, we compared six cropping systems ranging from diverse, organic systems to less diverse conventional systems conducted at two sites in southern Wisconsin. The results of 13 yr at one location and 8 yr at the other showed that: (i) organic forage crops can yield both as much dry matter as their conventional counterparts and with quality sufficient to produce as much milk; and (ii) organic corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and winter wheat (Triticum aestivum L.) can produce 90% as well as their conventionally managed counterparts. The average yields for corn and soybean, however, masked a dichotomy in productivity. Combining Wisconsin Integrated Cropping Systems Trial (WICST) data with other published reports revealed that in 34% of the site-years, weed control was such a problem, mostly due to wet spring weather reducing the effectiveness of mechanical weed control techniques, that the relative yields of low-input corn and soybean were only 74% of conventional systems. However, in the other 66% of the cases, where mechanical weed control was effective, the relative yield of the low-input crops was 99% of conventional systems. Our findings indicate that diverse, low-input cropping systems can be as productive per unit of land as conventional systems.

Abbreviations: GDD, growing degree days • NIRS, near infrared spectrophotometry • REML, restricted maximum likelihood • RFV, relative feed value • WICST, Wisconsin Integrated Cropping Systems Trial

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Received for publication February 9, 2007.