URBANA, Ill. — While the economic and environmental benefits of no-till farming have been widely hailed, the practice alone won’t do much in the long run to boost global crop yields, a key production goal as the world’s population continues to climb.

That’s the gist behind an international study that examined more than 5,400 field examples from all regions of the world, as well as results from more than 600 yield studies going back at least 15 years. A total of 48 crops were included.

The meta-analysis was undertaken by a team of scientists and researchers from Zhejiang University in China, the University of California, Northern Arizona University, the Swiss Federal Institute of Technology, the USDA and the University of Illinois. U of I crop sciences researcher Cameron Pittelkow is a co-author of the report, which was first published in Nature and can be found online at www.nature .com

No-till farming, along with other conservation agriculture practices of regular crop rotation and crop residue retention, has been ballyhooed as being more kind on pocketbooks and the environment, yet Pittelkow and study colleagues came to a surprising conclusion: Yields in almost all cases are significantly less than in traditional tilling practices.

“This raises some important questions about whether conservation agriculture has the capacity to play a major role in the sustainable intensification of agriculture, as is commonly assumed,” Pittelkow said. “We found if one is implementing conservation agriculture, it is critical to also adopt the principles of crop rotation and residue retention to minimize yield reductions.”

According to the review, no-till farming without rotating crops and without the benefit of crop residue – used mostly for cattle feed – reduced yields overall by nearly 10 percent. With the benefit of rotation and crop residue, yields declined by just 2.5 percent.

“Our analysis indicates that the potential contribution of no-till to the sustainable intensification of agriculture is more limited than often assumed,” the report states.

One key exception was how well no-till did in drier climates, without irrigation but with the rotation of crops and the use of crop residues. Under those conditions – in parts of Africa and southern Asia – yields improved on average by about 7.3 percent.

While approximately one-third of the world’s population lives in those drier climes, the study notes no-till practices exist only on about 9 percent of the land farmed. Researchers billed the review as “the first global assessment of previous research findings to try and identify whether no-till has a yield advantage or disadvantage compared to conventional tillage practices.”

Study co-author Chris van Kessel, with UC-Davis, summed it up: “Our findings suggest that broad implementation of conservation agriculture may not be warranted in all areas, particularly where residue retention and crop rotation practices are hard to implement.”