|ROBERTSON, G. PHILIP|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2007
Publication Date: 11/1/2007
Citation: Smith, R.G., Menalled, F.D., Robertson, G. 2007. Yield and Temporal Yield Variability Under Conventional and Alternative Management Systems. Agronomy Journal.99:1629-1634.
Interpretive Summary: The goal of this study was to assess average and year-to-year variation in yields of corn, soybean, and winter wheat grown in rotation under four different crop management systems: conventional, no-till, low-input, and organic. The study was conducted in SW Michigan at the W.K. Kellogg Biological Station Long-Term Ecological Research site. The crop yield data was collected over a 14 year period and showed that over that time yields were similar in the conventional, no-till, and low-input systems and were higher than those in the organic system. Over all, yield variability was lowest in the conventional and no-till systems, intermediate in the low-input system, and highest in the organic system. Results of this study suggest that, in terms of yields and year-to-year yield variability, no-till and reduced-input management systems are a viable alternative to conventional management in SW Michigan. Additional research will be required to improve the longer-term performance of the organic management system assessed in this study.
Technical Abstract: Year to year variation in yield is an inherit risk associated with crop production and many growers rely on intensive mechanical or chemical inputs to secure crop yields in the face of fluctuating environmental conditions. However, as interest in alternative approaches to crop management which are less dependent on external inputs grows, determining the degree to which management systems can impact the temporal variability of yields will help inform the development of sustainable agroecosystems. This study assessed average crop yields and temporal yield variability over a 14 year period in four agricultural management systems that are part of a long-term cropping systems experiment at the W. K. Kellogg Biological Station LTER (Long Term Ecological Research) site in SW Michigan. The four systems studied follow a corn (Zea Mays L.), soybean (Glycine max (L.) Merr.), and winter wheat (Triticum aestivum L.) three-year rotation under conventional (CT), no-till (NT), low-input (LI), or 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 in the rotation from 1993 to 2004. Averaged over the study period, yields in the CT and NT systems were similar across all phases of the rotation and of higher magnitude than the LI system only in the winter wheat phase of the rotation. Compared to the other three management systems, yields in the ORG system were lower in the corn and winter wheat phases of the rotation. However, yields in the soybean phase were similar across the four studied systems. Temporal yield variability differed among management systems and rotation phases and was highest in the ORG system. Compared to the CT system, yield variability was lower in the LI (corn phase) and NT (soybean phase) and similar in the NT (corn and winter wheat phases) systems. Results of this study suggest that long-term crop yield and temporal yield variability under alternative management systems such as no-till and low-input can be comparable to that in conventional systems. However, temporal yield variability can be relatively high in organic cropping systems.