No-till farming yields are low, and the conservation strategy faces a crisis

Compared with conventional tillage systems, no-till often leads to lower output. However, no-till has still shown yield gains in dry regions.

No-till farming, a key strategy based on conservation agriculture, can prevent conventional tillage from damaging the soil, yet it may not offer hope for boosting crop yields in most parts of the world. This conclusion comes from a new large-scale meta-analysis report by an international team at the University of California, Davis.

As a core principle of conservation agriculture, no-till has been working to promote the sustainable satisfaction of global food demand worldwide. However, after accounting for the results of 610 peer-reviewed studies, researchers found that compared with conventional tillage systems, no-till often leads to lower output. However, no-till has still shown yield gains in dry regions. This landmark study was published online in the journal Nature.

“A major challenge in agriculture is that we need to further increase production while also greatly reducing environmental impact,” said Cameron Pittelkow. While a postdoctoral scholar at UC Davis, he co-authored this research report and is now a faculty member at the University of Illinois.

“According to our findings, the common assumption that no-till will play a major role in sustainable, intensive agriculture does not necessarily truly hold,” he said.

Conservation agriculture is practiced on 1.25 million hectares of land worldwide, almost as large as the total cultivated land area of the United States. The three guiding principles of conservation agriculture are: minimize soil disturbance (also called no-till farming), protect the soil through cover crops or crop residues, and rotate crops.

The goal of conservation agriculture is to improve long-term productivity, increase profitable output and ensure food security, which is especially important under the threat of climate change. Because conservation agriculture avoids tillage, it is less time-consuming and can be more cost-effective than conventional tillage methods. However, in recent years, some disagreements have emerged about the impact of no-till farming methods on yields.

“This study was an arduous task, and it is also very likely the largest meta-analysis done in agriculture,” said another co-author, Bruce Linquist, a cooperative extension specialist at UC Davis.

After evaluating more than 5,000 parallel observational records, the researchers concluded that, on average, no-till farming has a negative impact on yields globally, although there are also several opportunities where yields come extremely close to or even exceed conventional tillage yields.

For example, when yield reductions are minimized, the principles of practicing crop rotation and retaining residues should be followed. Emphasizing the implementation of the principles of conservation agriculture is part of three integrated management systems, rather than practicing only no-till farming.

In addition, compared with the combined form of the other two principles of conservation agriculture under dry climates, no-till farming clearly performs better than conventional tillage, which may be due to higher soil moisture content.

Globally, 38% of people live in dryland ecosystems. Millions of acres of land in sub-Saharan Africa and dry regions of Asia have been identified as suitable for intensive development. However, the researchers also warned that no-till can be implemented in dryland areas to increase yields, but the other two principles of conservation agriculture cannot be absent.

In humid climates with sufficient precipitation, no-till farming actually produces on average 6%-9% less than conventional tillage.

“No one has ever verified that such a similar obvious decline would occur,” said Chris van Kessel. He is a professor of plant sciences at UC Davis and a co-author of the research report. “Our findings show that the widespread implementation of conservation agriculture may not be guaranteed in all regions, especially in regions where crop rotation and residue retention are difficult to satisfy.”