Inspirational ideas: Making rice cultivation resistant to soil salinisation

Spanish Ebro Delta acts as testing lab to make rice cultivation resistant to soil salinisation 

The rice fields in the Spanish Ebro Delta produce 90,000 tonnes of rice every year. But the future of this rice is threatened by soil salinisation, caused by rising sea levels and erosion of the Delta. Besides, the apple snail, a tropical pest introduced in the area, is ravaging rice crops by eating and uprooting young plants. A local Operational Group is testing how rice dry seeding can reduce the apple snail population and how this affects soil salinity.  

The Operational Group is coordinated by PRODELTA and includes several partners working with farmers and irrigators. The Catalan Institute of Agrifood Research and Technology (IRTA) conducts the research. “Dry seeding consists of seeding the rice in moist soil uncovered by water. This stops the snails entering the fields and damaging the young plants. Snails overwinter in the soil, but when the soil is kept dry, they can’t bury themselves. So in spring there are no snails left to damage the young rice plants. However, when there is no layer of fresh water covering the fields, sea water is more likely to enter the soil”, says farmer Miguel Tomàs Ferré. He is involved in the Operational Group. “Once the rice seedlings have grown tall enough to withstand the snail attacks, the fields are inundated intermittently, until the rice plants have reached their full height. The rice fields are continuously monitored to check the soil salinity during this process. The yields of rice grown under this system of dry seeding and intermittent irrigation during the early growth stages were compared with rice grown traditionally.” 

“We found that flooding the fields intermittently reduces the apple snail population and there is no negative effect on soil salinisation. Besides, we can keep the soil dry between 22 and 24 days before harvesting, but this depends on the rice variety and the type of soil. We also found that on sandy soils the yield was slightly less. On clay soil the yield increased by 3% with intermittent flooding. We will use these results in the future, since this system is the only one we can use in the lands affected by the invasion of the apple snail. Therefore, it is the only strategy if we want to keep producing rice”. 

Albert Pons is one the farmers that started dry seeding since 2015. He tells: “In relation to the control of the apple snail, we got 100% of control over the population. Four years ago, there was 40% less yield with dry seeding in comparison to traditional seeding. But, thanks to testing irrigation, fertilising, fertiliser fractioning techniques and adaptation of rice varieties to this system we achieved the same production as in a traditional system. Besides, it also helped a lot being part of a Catalan union that gathers 70% of the farmers here. The technicians of this union make a lot of tests in cooperation with the IRTA. So they proposed them the techniques that we as farmers are using for the dry seeding. Thanks to this symbiosis, I could fine tune the dry seeding technique in such a way, that no production is lost anymore in comparison to traditional practices”.

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