Substances from corn roots influence wheat yields

Wheat field on the Agroscope trial site in Posieux FR. Image: Valentin Gfeller
Wheat field on the Agroscope trial site in Posieux FR. Image: Valentin Gfeller

Corn roots secrete certain substances that affect the quality of the soil. In certain fields, this effect increases the yield of wheat planted after corn in the same soil by more than 4%. This has been demonstrated by researchers at the University of Bern. Although the findings from several field experiments show that such effects are highly variable, they could nevertheless contribute in the long term to making the cultivation of cereals more sustainable without additional fertilizers or pesticides.

Plants produce a wealth of specialized chemical substances. Some of these are also released into the soil, influencing its quality. This in turn influences the next plant that grows in this soil. The extent to which the secreted substances can be used in agriculture to increase productivity is still poorly understood. Researchers at the Institute of Plant Sciences (IPS) at the University of Bern have now conducted field experiments on this subject. With their findings, which were published in the journal eLife , the researchers have demonstrated that chemical substances from the roots of the corn plant can increase the yield of the following wheat - and this under agriculturally realistic conditions.

How corn root substances influence wheat

It was known from earlier studies by researchers at the Institute of Plant Sciences (IPS) at the University of Bern that so-called benzoxazinoids - chemical substances that corn plants release through their roots - change the composition of microorganisms in the soil at the roots and thus influence the growth of subsequent plants in this soil. The present study now investigated whether such so-called plant-soil feedbacks also occur under agriculturally realistic conditions. ’Such field experiments are essential to test the transferability of basic research into practice and thus a possible agronomic benefit’ says Valentin Gfeller, who worked on the project as a PhD student at IPS and is now employed at the Research Institute of Organic Agriculture FiBL. In a two-year field experiment, two maize lines were first grown, only one of which released benzoxazinoids into the soil. Subsequently, three varieties of winter wheat were grown on the differently conditioned soils. Thus, it was shown that the release of benzoxazinoids resulted in improved emergence, increased tillering, increased growth and increased yield.

Fewer pests, same quality

In addition to increased yield, lower infestation by certain pests was noted. ’A 4% increase in yield doesn’t sound spectacular, but it is significant when you consider how difficult it is now to increase wheat yields without additional inputs,’ says Matthias Erb, professor of biotic interactions at the Institute of Plant Sciences, who led the study together with Klaus Schläppi of the University of Basel. ’Whether such effects really make a difference on a large scale in agricultural applications remains to be seen, however, as yield also depends on many other factors,’ Erb says. The study shows the potential of using specialized plant compounds to improve crop productivity through variety-specific crop rotations.

Thanks to collaborations within the Interfaculty Research Cooperation (IFK) ’One Health’ of the University of Bern (see box), it was also possible to investigate the quality of wheat at the level of individual chemical elements. Together with the Geographical Institute of the University of Bern and Agroscope, the federal competence center for agricultural research, it could be shown that the increase in yield by benzoxazinoids has no negative effect on the quality of wheat.

Plant substances survive in the soil

To better understand the underlying mechanism, the researchers conducted various soil and root analyses. Benzoxazinoid-producing plants accumulated these substances and their degradation products in soil close to the roots. In addition, in collaboration with the University of Basel, it was confirmed that benzoxazinoids affect the community of bacteria and fungi in and on the maize roots. However, the soil nutrients were not changed. The benoxazinoids also proved to be particularly long-lived in the soil. The extent to which wheat growth and overall yield are affected by the benzoxazinoids, either directly or indirectly through the microorganisms in the soil, will be studied in more detail.

Soil texture is crucial

To test the effects of different environmental factors, the research team, together with the University of Basel and Agroscope, conducted another two-year field experiment to see how these plant-soil feedbacks from benzoxazinoids behaved in a more heterogeneous field. The composition of soil chemistry and microorganisms in this field varied greatly. The researchers were able to show that the impact of benzoxazinoids on wheat growth and resistance depended on this varying composition. ’A better understanding of the effects of soil composition on plant-soil feedbacks is crucial for future use in sustainable agriculture,’ says Valentin Gfeller.