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EJP-Soil First call: SoilsalAdapt Preadapting soil biology for increased tolerance to elevated salinities due to climate change

Alternative title: EJP-Soil – SoilsalAdapt. Forhåndstilpasning av jordbiologien for å øke dens toleranse for klimadrevet økning i saltinnhold

Awarded: NOK 3.8 mill.

Salinity is an important cause of the deterioration of agricultural land in dry areas, as well as areas threatened by climate-driven sea level rise, where crop reduction is a common consequence. If soil as an ecosystem can "learn" to tolerate saline irrigation through the gradual adaptation of soil organisms, this means that farmers can prepare their soil to remain fertile despite having to resort to the use of saline water for irrigation at times. Farmers will then be able to deal with an ever-increasing problem of salinization of arable land. Little is known about how soil organisms react to increased salinity. Research nevertheless shows that soil organisms from saline soil are more tolerant of salt than those from non-saline soil. Based on this, the project will test how the adaptability of soil organisms works when exposed to different salt water concentrations in soil, as well as measure and predict effects on different scales. The Norwegian partner in the project is NMBU at the Faculty of Environmental Science and Nature Management. In 2023, we carried out a successful trial of growing grass in soil that had previously been irrigated with salt water in a pot trial in England. We have received 3 soil types with increasing salt water treatment. It has proven to be difficult, but we have found a possible solution to the problem and we will continue beyond 2024. The aim is to be able to measure the interaction of soil microorganisms with plant roots at different degrees of salt stress. After the end of the experiment, soil samples are taken at an increasing distance from the plant roots, and this will give an answer as to whether plants and microorganisms in interaction increase the tolerance for salt. In 2024, we will also measure their potential ability to drive denitrification. It will give us answers to whether tolerance impairs the ability to operate important ecological functions.

Saltwater contamination is a major contributor to soil degradation in arid areas. In temperate coastal areas dry periods force freshwater level closer to the saline water. The ground water will become increasingly brackish. Growers are faced with either: 1) irrigating with much more expensive treated tap water; or 2) not irrigating which significantly increases the chance of crop failure. Growers are increasingly forced to use the part-saline ground water for irrigation in summer, but the short- and long-term effects are poorly understood. Soil organisms are key to soil fertility, but very little is known about how they respond to increased salinity. Previous work show that saline irrigation affects soil communities, and that soil organisms from saline soils are more tolerant to salt than those from non-saline soils. We will tests whether Darwinian selection processes can ‘push’ soil biological communities to become increasingly tolerant of saline conditions by adaptation. We will test a range of saline concentrations, measure and predict the various impacts of this approach at three scales. At the micro-scale the NO partner will focus on the effects on the rhizosphere. The UK partner will look at medium-scale pot to whole field-scale changes in total soil biodiversity and function by R&DNA sequencing and compare the fertility of soils of various history of saline concentrations in the UK and Portugal. We will also measure any cost of saline irrigation and adaption and how long any effects last. Lastly, the landscape-scale impacts of increased salinity will be modelled by the PT partner, to predict the European and global extent of the issue, and identify the management practices to counter salinization and conserve the soil functions. If soils can ‘learn’ to tolerate saline irrigation through more gradual biological adaptation, growers may condition soils to remain fertile despite the use of saline irrigation and manage this increasingly pressing issue.

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