Breeding nutrient-efficient maize varieties: Good maize yield despite less fertiliser – how does that work?

December 14, 2017, Reading time: 3 minutes

Germany has restricted the permissible amount of nitrogen in many fields with the new Fertiliser Ordinance. In many places only little fertiliser may be used. Nevertheless, farmers want to continue to generate good yields, for example with maize. To support them, KWS breeds maize varieties, which absorb nitrogen from the soil more efficiently and can therefore cope with somewhat less nitrogen. This is one of the contributions plant breeding makes to sustainable agriculture.

One of the reasons for recasting the regulation: From the perspective of legislators, the nitrate concentration in groundwater is often too high. The authorities believe that agriculture contributes to this. If nitrate is not absorbed by plants, it can be washed out in the rain. This is the case, for example, if too much is fertilised or at the wrong time. Therefore, in future, the amount of nitrogen should be adjusted as accurately as possible to the needs of the plants, and kept as low as possible. In other countries, legislators dictate this. In addition, the Fertiliser Ordinance obliges German farmers to produce an exact nutrient balance for their fields.

Useful consequence of genetic variation

"It means that maximising the efficient use of nitrogen by plants plays an even greater role than before," states maize breeder Thomas Presterl from KWS. But how do you keep the yield stable, when many fields will receive less nitrogen in the future? "Of course, no plant can manage without a certain amount of nitrogen, it is one of the most important plant nutrients," says Presterl. "But our research has shown that some maize plants absorb nitrogen more efficiently than others. This is the result of natural genetic variation," explains his colleague Roland Peter, also an expert in maize breeding at the independent plant breeding company.

As a result, nitrogen-efficient varieties show superior performance with a low supply of nitrogen, compared to other varieties. Nitrogen-efficient varieties still have a decent yield even under deficiency conditions: "A variety should use the plant-available nitrogen in the soil as efficiently as possible from the beginning of growth, before it is shifted into deeper layers or released into the air. The most important requirement is that maize varieties with limited fertilisation do not suddenly drop sharply in their yield, but maintain a high level of performance," explains Presterl. Yield security is one of KWS’ priority breeding objectives.

KWS breeders and researchers examine such maize plants, explains Peter: "For example, we grow them in fields with very little nitrogen and look to see which maize plants cope best under these conditions." One reason is, for example, that plants with a particularly widely branched and dense root system have more contact with the soil and therefore can absorb a little more nitrogen, explains Presterl. His colleagues investigate the natural genetic make-up of plants. It turns out that the desired property of nitrogen efficiency, although in many cases hereditary, is not the sole determinant.

A long-term task

In addition: Agriculture is always part of and within nature. Therefore, field conditions differ from year to year. Of course, this also applies to the nutrient uptake of maize and all other plants. This in itself is a long-term task: Breeding a new variety takes around ten years. It requires not only scientific expertise, but also entrepreneurial freedom and independence. KWS has had both of these for more than 160 years.

The company has been involved in the breeding of nitrogen-efficient maize for several years. Therefore, many of the current varieties already have good nutrient uptake, among other things, due to their good root system. Which, and how many, hereditary factors interact with each other and in which ways, is not yet known in detail - this still means a lot of work for researchers at KWS. To achieve this goal, the company also invests around 17 percent of its sales in research and development. The aim is always to increase the genetic diversity of crop plants in order to provide farmers with the best quality varieties.

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Thilo Resenhoeft
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