Chemicals derived from maize roots have an impact on wheat yield.

 

Maize roots release compounds that have an impact on soil quality. In certain farms, this impact enhances wheat yields planted after maize in the same soil by more than 4%. This was demonstrated by University of Bern researchers. While the results of multiple field trials demonstrate that these effects are very unpredictable, they may nonetheless assist to make grain agriculture more sustainable in the long run, without the need for extra fertilizers or pesticides.

Plants create a plethora of unique compounds. Some of these are absorbed by the soil and have an impact on its quality. This, in turn, has an impact on the next plant that grows in the soil. So yet, little study has been conducted on the extent to which excreted chemicals can be employed to boost agricultural output.

However, researchers from the University of Bern's Institute of Plant Sciences (IPS) have recently undertaken field studies in this region. The researchers' findings, published in the scientific journal eLife, show that specialized metabolites from the roots of the maize plant may improve the yields of later planted wheat under agriculturally realistic conditions.

How maize root chemicals affect wheat:

Previous research conducted by researchers at the University of Bern's Institute of Plant Sciences (IPS) revealed that so-called benzoxazinoids—natural chemicals released by maize plants through their roots—change the composition of microorganisms in the soil on the roots and thus influence the growth of subsequent plants that grow in the soil. The current study looked at whether such plant-soil feedbacks occur under genuine farming circumstances.

"Such field experiments are essential to test the transferability of basic research into practise and thus assess the potential agronomic benefit," says Valentin Gfeller, a doctorate student at IPS who now works at the Research Institute of Organic Agriculture FiBL. Initially, two lines of maize were planted in a two-year field experiment, with only one of them releasing benzoxazinoids into the soil. Three winter wheat cultivars were then cultivated on the various soil conditions.

On this basis, it was feasible to show that benzoxazinoids excretion promotes germination and boosts tillering, growth, and crop production.

Fewer pests, same quality:

In addition to higher crop yield, decreased levels of insect infestation were reported. "A yield increase of 4% may not sound spectacular, but it is still significant given how difficult it has become to increase wheat yields without additional inputs," said Matthias Erb, Professor for Biotic Interactions at the Institute of Plant Sciences and co-author of the study with Klaus Schläppi of the University of Basel.

"Whether effects of this kind actually make a significant difference for overall agricultural productivity and sustainability remains to be seen, however, as yield also depends on many other factors," Erb says. The research shows that employing specialised plant chemicals to boost agricultural output through variety-specific rotations has the potential to be beneficial.

It was also able to evaluate the quality of the wheat at the level of individual chemical constituents within the scope of the "One Health" Interfaculty Research Cooperation (IRC) at the University of Bern (see box). It was feasible to establish, in collaboration with the University of Bern's Institute of Geography and Agroscope, the Swiss centre of excellence for agricultural research, that the increase in harvest caused by benzoxazinoids had no detrimental influence on wheat grain quality.

Plant chemicals persist in the soil:

To further understand the underlying process, the researchers performed soil and root analyses. These compounds and their breakdown products were deposited in the soil around the roots of benzoxazinoid-producing plants.

Furthermore, it was demonstrated in partnership with the University of Basel that benzoxazinoids alter the population of bacteria and fungus in and on maize roots. However, no changes were made to the soil nutrients. Benzoxazinoids were also shown to be quite persistent in soil. The extent to which benzoxazinoids impact wheat development and yield directly or indirectly via soil microorganisms will be investigated further.

Soil properties are important:

The study team undertook another two-year field experiment with the University of Basel and Agroscope to examine how these plant-soil feedbacks from benzoxazinoids function in a more diverse environment. The soil chemistry and microorganism composition in the field in question differed greatly. The researchers were able to demonstrate that the effect of benzoxazinoids on wheat development and resistance is dependent on the composition.

"A better understanding of the effects of soil properties on plant-soil feedbacks is crucial in terms of future use in sustainable agriculture," says Valentin Gfeller.