Open day turns the spotlight on subirrigation

Practical test of sustainable fresh water supply system for agriculture

All eyes were on a test array for ‘underground irrigation’ at the Rusthoeve Test Farm in Zeeland on 7 and 8 July. Since the summer of last year, KWR and KnowH2O have been conducting practical trials with a sustainable freshwater supply system for agriculture. Farmers, water and soil specialists showed considerable interest and people see adjustable drainage with subirrigation as a useful way of anticipating extreme weather. In addition, local conditions also have to be taken into account.

At the Rusthoeve Test Farm (in Colijnsplaat, NL), KWR and KnowH2O are looking at whether and, if so, to what extent the system of controlled drainage with subirrigation can be used here to supply fresh water for agriculture. The aim of subirrigation is to provide growers with possible irrigation alternatives. In order to establish a dialogue with the end users, KWR researcher Janine de Wit explained how the system works to interested farmers and experts from the water and soil sector. Obviously, the primary focus is on the results. This project was made possible by a subsidy from the Province of Zeeland.

Higher crop yield

‘We saw clear effects in 2020,’ says De Wit. ‘During the dry summer of that year, subirrigation allowed us establish a higher groundwater level,  improving moisture management for the crop. Crop yields were higher with subirrigation than in areas where no water was brought in.’

Controlled drainage with subirrigation

Visitors to the open day at the Rusthoeve Test Farm see controlled drainage in combination with subirrigation as a convenient way of anticipating wet and dry weather extremes, De Wit concludes from the reactions. A number of them are already trying it out. ‘They asked how the system could be used more efficiently and what the long-term effects would be. Those are precisely the questions we are working on now. It is good to see that people understand how urgent this issue is and that they are taking the appropriate action. There’s a real sense that controlled drainage with subirrigation can help agriculture.’

Resilience to climate change

De Wit acknowledges that the underground irrigation approach is no silver bullet. ‘Certain preconditions have to be met, such as the condition of the soil. And obviously, there has to be enough water available for subirrigation. That also became clear from the discussions during the open day. But that’s okay, we’re still learning a lot. Not just in the clay soil of Zeeland but also, for example, in Dutch sandy soils. Similar systems are being used there and studied in the KLIMAP project. Ultimately, the aim of our research is to make our country resilient to the effects of climate change across the board.’

Visitors to the open day were driven past the test facility on an open cart in line with corona regulations.