A recent report from USDA’s Agricultural Research Service has some interesting insights on the benefits of crop rotations, but researchers caution the “long view” is needed to fully capitalize on such improvements.
Many growers know crop rotations can rebuild soil health, fight pests and diseases, and spread-out season-to-season risks from markets, political mandates and weather. Still, widespread adoption of increasingly-diverse rotations generally gets stalled by short-term (but economically important) views on commodity prices of one or two specific crops included in that rotation.
Years of research are favoring increasing diversity in existing crop rotations, however, particularly when looking at long-term returns in the face of seemingly growing instability in all the variables facing growers today.
ARS agroecologists recently compiled data from 20 long-term experiments spanning 60-years comparing outcomes of different crop rotations across North America. Their aim was to assess changes in outcomes under different growing conditions for individual crops like corn or soybeans in various rotations.
They also examined outcomes of complete rotations (multi-year performance of a given rotation) as a whole – not cherry-picking performance of individual cash crops. The hope was to quantify the benefits and trade-offs of crop rotations.
The recent ARS abstract indicates outcomes tended to be better for individual crops when grown in more diverse crop rotations grown across all growing conditions – with outcomes of long-term use of complete rotations dependent upon which crops were in the rotation. A confusing statement for certain, but the bottom line seems to be “the more crops in rotation, the better, over the long term.”
“This shows the composition of crop rotations was a bigger factor than individual crop performance,” the authors say, adding diverse rotations improved outcomes of complete rotation cycles under poor growing conditions, which shows how diverse rotations can reduce risk of crop loss in changing climatic conditions.
“To our knowledge, no long-term, multi-site studies have attempted to understand the effect of changing the rotation on the performance of the complete rotation and its component crops simultaneously,” says Kathrine Muller, ARS Ecologist.
Muller explains while many farmers face hurdles diversifying their crop rotations because doing so requires more management and possibly acquiring new equipment, the benefits of such diversification can reduce the amount of fertilizer or pesticides needed to maintain productivity.
“Though effective, more diverse rotations may take years to show results, however,” she adds.
Muller says the report comes from a collaboration of universities and agricultural entities called the DRIVES Network (Diverse Rotations Improve Valuable Ecosystem Services) and that effort is ongoing as the results of more long-term experiments are added to the project. Researchers will be looking at the overall effects of drought, and slow-moving variables such as changes in soil characteristics.
