Wetenschap - 18 februari 2016

Phosphate input on grassland must rise substantially (outside the Netherlands)

tekst:
Albert Sikkema

The soil fertility of grassland in the world is declining, because grassland is receiving too little fertilizers. To keep the grass cultivation for the production of milk and meat at the same level, the phosphate input needs to double the coming years.

This was stated by researchers from Wageningen, Utrecht, the Netherlands Environmental Assessment Agency and the FAO in the scientific journal Nature Communications. Global improvements in grassland management could see grasslands taking on a more important role in food production, according to researchers, including professor Martin van Ittersum of the Plant Production Systems Group.

The Netherlands and other parts of Northwest Europe have troubles with a phosphate surplus, which means that farmers apply too much fertilizer on grass and arable land. But by far the largest part of the three billion hectares of grassland worldwide receives no or little fertilizers. That is why the phosphor in the soil, which is absorbed by the grass, is not supplemented. Much grassland is exhausted.

To be able to continue to produce enough grass for the current livestock in the world, especially the phosphate input needs to be increased, the researchers calculated. With a duplication of the phosphate input on grassland, the current production of grass and arable land remains at the same level. But if we want to intensify the grass production with 80 percent to produce more milk and meat for the growing world population, the phosphate input would have to be increased by a factor of four.

A better and higher production of grassland can additionally ensure that cows and goats will need less grain, the researchers state, so that more grain become available for human consumption.

Globally, grassland makes up two-thirds of the agricultural land. The largest part of this area is not systematically grazed or mowed. Also, they are generally not fertilized. The grass absorbs nutrients such as phosphor from the soil. After the grass is eaten by cattle, the phosphor ends up in the stomach of the grazer. The phosphor leaves the body of the animal through the manure, but only half of the manure ends up on the grassland – the other half is used for vegetables and agriculture. In this manner the grassland is slowly exhausted.


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