Crops will protect nitrogen against loss

Crops need less nitrogen if they have more ammonium around their roots. Plant breeders are therefore working on crops that release substances from their roots that counteract the transformation of ammonium into nitrate. The first wheat varieties with these natural nitrification inhibitors are expected on the market in five years.

Plant breeders are developing crops that actively counteract nitrogen losses. Roots of these crops release substances that reduce the transformation of ammonium into nitrate. These compounds – they are called nitrification inhibitors – inhibit the soil organisms that are responsible for this transformation process. Ammonium is less sensitive to leaching than nitrate. Soil bacteria can also transform nitrate into nitrous oxide, a powerful greenhouse gas. Whether crops themselves benefit from a high ammonium content in the soil has not yet been sufficiently investigated, according to an analysis by the popular science magazine Plant nutrition courier. There are indications, however, that fertilisation with ammonium stimulates the formation of nitrification inhibitors in the roots of some grasses.

For decades, scientists have been looking for ways to improve nitrogen use by crops. This could reduce nitrogen application rates and reduce losses to the environment. One of the possible measures is the addition of synthetic nitrification inhibitors to fertilisers. Biologists have discovered grasses that produce natural variants of nitrification inhibitors in their roots. Plant breeders from the International Maize and Wheat Improvement Center (CIMMYT) have transferred this trait to wheat. The first wheat varieties with these nitrification inhibitors are expected on the market in five years. Research into maize and rice with these inhibitors in the roots is in full swing. Nitrification inhibitors have also been found in roots of perennial ryegrass, but the amount is too small for a noticeable effect under practical conditions. Ribwort plantain does contain large amounts of a natural nitrification inhibitor. Researchers are studying whether ribwort plantain can improve the nitrogen balance of grassland. Ribwort plantain in fodder mixtures improves the nitrogen balance in cattle and sheep, New Zealand research has shown. Seed companies in New Zealand have grown varieties of ribwort plantain suitable for inclusion in pasture mixtures.