Why scientists look to the soil when rain stops falling

Wageningen University & Research is opening this academic year by putting the water-food connection on the map. This is really important, believes Arjen Budding, Sustainable Water Management programme leader. “Last year, the United Nations organised the first water conference in 50 years. At that conference, only two of the one hundred and eighty side events addressed the relationship between food and water.” Yet climate change is affecting rainfall all over the world, making some regions drier and others much wetter. “That has an impact on food production.”

A good example are the regions around the Mediterranean, where rainfall is decreasing and temperatures are rising. For agriculture that relies heavily on rain, such as olive groves, this is obviously a problem. Some farmers quite naturally switch to irrigation. “But that’s a short-term solution, because even that water has to come from somewhere,” Budding explains. “Instead you should check the soil the olive trees grow in. Healthy soil acts like a sponge and retains a lot of water. That means you can do more with the rain that does fall.”

Healthy soil retains water

Budding spent many years working with the Dutch Water Boards. “Traditionally, the principle was: water level follows function. In other words, we assign a function to the land and provide the water level to match.” According to Budding, this idea of social engineering is not only practiced in the Netherlands. Mediterranean olive, wine and almond farmers also try to bend nature to their will by increasing irrigation.

In Castilla La Mancha, a Spanish region the size of the Netherlands, Wageningen Environmental Research is working with local farmers and government agencies to investigate how growers can adapt to decreasing rainfall. “Our advice is to ensure healthy soil. Here's the thing: soil with lots of life and organic matter is more porous and therefore holds more water. Farmers in Castilla can profit from that.”

To move towards healthier soil, Spanish farmers need to plough less. Although ploughing counteracts weeds, it also exposes soil life to the hot sun, causing it to die. “Instead, we recommend using cover crops under the trees, for example. These also combat weeds while their roots prevent wind erosion.”

Sustainable use of water

“With respect to water and food, we need to reverse the traditional principle. Function should follow water level, not the other way around,” Budding argues. “That basically means we are going through a water transition. Natural systems - also water cycles - will form the basis for our food production. Working with the soil is an important part of that.” Budding explains that cultivation systems need to be adapted accordingly, like in Spain, or even change completely. “Farmers then switch to other crops, for example, which are more resilient to drought.”

To support that transition with research, Budding and colleagues took the initiative to connect the water researchers from Wageningen University & Research: Water@WUR. “Sustainable water management is important to continue producing enough food in the future. For this, we don’t just need technical innovations, or fundamental research, but also political experts and sociologists. In Castilla, for example, not all farmers simply switch to the proposed solutions. Some farmers aren’t convinced by scientific studies. Other strategies are needed to generate interest, support and trust at a regional level.”