Inauguration of Gerard Velthof: Unification of fertilizer, nitrogen and climate policy

Gerard Velthof studied soil science and soil fertility in the 1980s and spent most of his career at WUR. As an expert in soil, nutrients, emissions and leaching, he gathers scientific knowledge to inform government policies. Since 2000, he has also held this position in the Commissie van Deskundigen Meststoffenwet (CDM) at the Ministry of Agriculture, Nature and Food Quality. “My topic is extremely timely now that the derogation must be gradually abolished in line with European legislation. However, the debate on manure is not new: it has always been there.”

Amid all the debates and social unrest in the agricultural sector, Velthof focuses on knowledge in the long term. As a professor in the Soil Biology department group, he intends to continue and expand in-depth soil research in the coming years. These are not limited to manure: it will also focus on other environmental issues such as global warming.

Prevention of nitrous oxide emissions

The release of nitrous oxide from soil is a topic about which we still know too little. Nitrous oxide (N₂O) is a nitrogen compound released by agricultural land and is a major greenhouse gas. “I want to know more about when it will be released and how much it costs. You can then compare different conditions, whether there is a lot, little or no fertilizer, animal manure or artificial fertilizers, and whether it has rained a lot or been dry for a long time. This all makes a difference.

The problem with nitrous oxide is that it can counteract measures to combat global warming. This threat occurs, for example, in the case of peat bogs. Raising the groundwater level in peat bogs is intended to counteract carbon dioxide emissions resulting from the decomposition of dry peat. “However, wet peat actually releases nitrous oxide, a greenhouse gas that is more powerful than carbon dioxide,” notes Velthof. “We therefore want to measure and calculate the optimal groundwater level to counteract global warming.” Carbon storage in sandy and clay soils also releases nitrous oxide. “From a climate perspective, storing carbon in soil seems like a good solution, but we need to know where the balance is between storage and emissions.”

Knowing the soil for future policy

Using new measurement techniques, Velthof will better map the processes of nitrogen, carbon and phosphorus compounds in soil and emissions to air and water. This knowledge also ultimately helps formulate policies to combat emissions and leaching. It won’t make the job of decision-makers any easier, but it will hopefully make things more efficient. “With more basic knowledge, we can prevent agents from acting on each other. For example, injecting manure into the soil creates less ammonia but more nitrous oxide. You can take extra measures to prevent this from happening,” he explains.

Velthof admits that environmental problems in agriculture are significant, especially the problem with excrement. “In two years, the fertilizer surplus will be huge. All kinds of technical solutions can be imagined, but they are not completely quick to implement and only partially solve the problem. Restricting cattle breeding is necessary to comply with European law. That would be my advice, but the final decision rests with the politicians.