Annual crop yield variability under alternative management systems

Smith, R.G., F.D. Menalled, K.L. Gross, and G.P. Robertson

Presented at the ASM at Estes Park (2006-09-01 to 2012-09-23 )

Although it is often suggested that crop yields in conventionally managed agricultural systems are less stable from year to year than those in organic and reduced-input systems, there have been few studies that have directly examined this issue. The goal of this study was to determine the effect of agricultural management systems on the annual variability of crop yields over a 14 year period in a long-term cropping systems experiment at the W. K. Kellogg Biological Station LTER in Michigan. Crops were corn, soybean, and winter wheat grown in a three-year rotation under conventional (CT), no-till (NT), low-input (LI), and organic (ORG) management. Crop yields were measured each year, and crop yield variability was estimated using the coefficient of variation calculated separately for each crop phase of the rotation from 1993 to 2004. Mean yields for each crop phase were similar in CT, NT, and LI, and of higher magnitude than in ORG. There was a strong rotation phase by management system interaction on crop yield variability. Crop yield variability was lowest in CT and NT winter wheat and highest in ORG soybean. Results of this study suggest that, despite previous observations, crop yields in organic management systems are not always more stable than those in conventional systems. No-till and reduced input management systems perform comparably to conventional systems over the longer-term, both in terms of yields and annual yield variability.

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