Cropping systems in the Northern Corn Belt have been changing over time in response to several interacting biophysical and social factors. The current system, which is predominantly based on the corn-soybean crop rotation, conventional tillage, and chemical inputs, may not be sustainable in the long run. In addition, farmers in large parts of the Corn Belt are challenged to cope with yield variation over time (temporal variation) in the presence of soil variation within fields (spatial variation), knowing that temporal variation has a cyclical nature, is usually larger than spatial variation, and therefore has considerable impact on crop yields at the field, farm and national levels.
Cropping systems in large parts of the Corn Belt became more specialized during the last ~50 years; this trend is likely to disrupt many ecosystem functions, alter their capacity to provide a range of goods and services, and render them more susceptible to degradation over time. Therefore, long-term cropping systems research, in conjunction with the use of innovative experimental design and powerful statistical analyses procedures, were adopted to develop and verify alternative crop rotations and management practices that are capable of effectively reducing long-term yield variation.
Scientists at the USDA-Agricultural Research Service (ARS)-North Central Soil Conservation Research Laboratory in Morris, Minnesota, established a field experiment in 2002 at the Swan Lake Research Farm. The first part of this long-term study (2002-2005) evaluated the impact of current and alternative management practices and several phases of diversified crop rotation options on crop rotation yield and its temporal variation in the presence of soil spatial variation under conventional and organic cropping systems. Results from the study were published in the May-June issue of Agronomy Journal.
A combination of reductionist and whole system research approaches was employed to develop statistical models, reduce and visualize complex interrelationships between several soil physical, chemical, and biological variables, phases of crop rotations, management practices, and inputs in conventional and organic cropping systems’ databases.
Descriptive and measureable indicators have been developed to help identify and interpret possible causes of variation in total yield and its temporal variation in conventional and organic cropping systems. A classification scheme of cropping systems, crop rotations, and management practices was developed to help identify appropriate combinations of these factors that would result in large and stable yields. The scheme can be used as a guideline to identify stability in crop production, to plan the use of appropriate management practices for a given cropping system or crop rotation, and to maximize the chances of obtaining the largest and most stable yield over time.
Results of the study are useful in identifying causes of yield variation under certain soil conditions and management practices, and will help researchers, crop consultants, and farmers optimize input use, maximize the ability to detect true responses to management factors, determine trends and understand changes in yield over time, and assess long-term sustainability of alternative cropping systems.
Research is ongoing at the USDA-ARS-North Central Soil Conservation Research Laboratory, Morris, MN to investigate and model the impact of projected climate change on temporal variation of crop yields in an effort to help farmers make the right management decision at the right time and to be able to predict and control this variation.
source : soils.org
<>
