No-till farming may not offer the yield benefits once thought, an analysis of peer-reviewed studies on the topic led by the University of California, Davis has found.
Researchers found that no-till often leads to yield declines compared to conventional tillage systems, though it still shows promise for yield gains in dryland areas.
"The big challenge for agriculture is that we need to further increase yields but greatly reduce our environmental impacts," said Cameron Pittelkow, who co-authored the study as a postdoctoral scholar at UC Davis and is now on the faculty of the University of Illinois. "The common assumption that no-till is going to play a large role in the sustainable intensification of agriculture doesn't necessarily hold true, according to our research findings."
After assessing more than 5,000 side-by-side observations, the researchers concluded that on average no-till negatively impacts yields at the global scale, yet several opportunities exist for more closely matching or even exceeding conventional tillage yields.
For example, yield reductions were minimized when the principles of crop rotation and residue retention were also practiced, highlighting the importance of implementing all three conservation agriculture principles as part of an integrated management system rather than no-till alone.
Moreover, when adopted in dry climates in combination with the other two principles of conservation agriculture, no-till farming performed significantly better than conventional tillage, likely due to the higher retention of soil moisture.
Dryland ecosystems are home to 38% of the world's population, and millions of acres of land in arid regions of sub-Saharan Africa and South Asia have been identified as suitable for sustainable intensification.
Yet, the authors also caution that practicing no-till in dryland areas without the implementation of the other two principles of conservation agriculture – cover crops and crop rotation – decreases yields.
In regions with moist climates and sufficient precipitation, no-till farming actually resulted in yields that were on average 6% to 9% lower than with conventional tillage methods.
"No one has ever stated that there would be a significant decline like this," said Chris van Kessel, a professor of plant sciences at UC Davis and co-author of the study. "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."
The study, Productivity limits and potentials of the principles of conservation agriculture, was published online Oct. 22 in the journal Nature.