Adaptation to salinization for high-value cash crop agricultrue

The Climate change and salinization program for the northern Netherlands focused on the current and future impacts of salinization on high-value cash crop agriculture. A series of groundwater studies provided an insight into the role of tile drainage in salinization. Amongst others, research was performed into the ways tile drains contribute to the accumulation of salts in the topsoil.

The main conclusion of the studies is that the effects of drainage are twofold. On the one hand, tile drainage can prevent salinization when it functions as a barrier between fresh and saline groundwater in the rootzone. On the other hand, drainage can lead to the upward movement of the fresh-salt groundwater interface when pulling upward preferential flows. In addition, when the drains run dry saline water might end up in the rootzone by capillary rise. The described processes were measured during extensive field campaigns and modelled in a later stage.

During the studies it was found that scaling had a large impact on the research outcomes. For accurately calculating salt loads and concentrations in a polder, special attention had to be paid to scales. The optimal scales for collecting data and for simulating salinization processes were established through tests in a pilot polder. Along with other modelling tools, Sobek was used.

In a previous research, salinization risk maps were developed based upon a 5000 mg/l threshold. Because a 1000 mg/l threshold is much more informative for the agricultural sector, reviewed maps were generated based on this value. The differences between the maps indicate whether additional agricultural areas are, in light of the new boundary conditions, thought to be threatened by salinization. The 1000 mg/l threshold value adds detail to the results and provides new insights concerning agricultural productivity losses.

The described conclusions are a solid basis for research into the effectivity of small scale  interventions aimed to address agricultural productivity losses caused by droughts and salinization. Interventions directed at salinity problems and droughts do not only complement, but also reinforce each other. An integrated approach results in solid and cost-effective interventions.