Organic and Conventional Production Systems in the Wisconsin Integrated Cropping Systems Trial: III. Yield Trends

The Wisconsin Integrated Cropping Systems Trial (WICST) at Arlington, WI, compared five production philosophies in place of fixed treatments, which can be problematic, during 1990 to 2012. Corn (Zea mays L.) was the test crop common to the five cropping systems. All five cropping systems produced positive, average corn yield trends ranging from 0.1 to 0.2 Mg ha(-1) yr(-1). The overall rates in three conventional systems exceeded those in two organic systems; but the systems nearly equalized when better technology was introduced in the organic systems. Genetic engineering did not accelerate yield improvements. Hence the difference between conventional and organic systems has been largely due to the available technology, not agroecological factors. The yield advantage for corn following alfalfa (Medicago sativa L.) vs. continuous corn (the rotation effect) was 1.47 +/- 0.38 Mg ha(-1) with no linear or quadratic trends and with the largest values occurring in years with stresses that hindered corn development. Although all five cropping systems produced positive yield trends across two decades, that did not prove they were sustainable over the longer term. There was no clear advantage for either organic or conventional systems in regard to sustainability so the selection process should tailor the cropping system to the individual farm. The resulting picture is a dynamic agriculture with each cropping system encountering and solving challenges. Furthermore, it shows the benefits of long-term, cropping systems trials in providing base line data, monitoring time-trends, evaluating new technology, and examining sustainability issues.