Background

Irrigation water is a key factor in the production of rice and water quality has a major impact on crop yield as a result of tolerance of rice to factors such as dissolved salts. Due to increased water use in coastal areas, the sea intrudes the water table and seawater floods nearby fields during storms in the Mediterranean area. The result is increased water salinity, which reduces yield in rice crops and increases soil salinity.

Rice is one of the most sensitive crops to salinity. Rice is sensitive to salinity, particularly during the early seedling and pollination stages. Salinity stress during these periods may reduce rice growth and/or yield. Yield reductions have been observed when the Electrical Conductivity (EC) of irrigation water was higher than 1.9 dS/m.8 An EC of about 2.6 dS/m reduced the yield to 90 % with respect to 2.0 dS/m, and EC about 4.8 dS/m reduced yield by an additional 50 %.

Nowadays, water condition is for the most part assessed by visual inspection of the crops and, when excess water salinity is suspected, fields are irrigated by flooding them. In areas such the Ebro Delta where water salinity is endemic, rice paddies are continuously irrigated with freshwater to reduce water salinity. This is a remedial solution that requires enormous volumes of water and considerable energy is required to pump water from drainage channels into the sea, whereby drainage channels are deeper than the water table to drain salty water from it and from the paddies.

There is thus a real need to provide European rice producers with an effective tool for measuring the salinity in their water supplies in order to enable them to effectively manage and protect their rice cultivations, while at the same time safeguard water supplies and the environment.

Water salinity can be accurately determined by measuring its electrical conductivity (EC). Measuring EC at the water inlet and outlets of the cultivated areas can help in monitoring the “washing” effect of irrigation. Measuring EC at different depths in drainage channels can help in managing water salinity in larger areas. Measuring EC of reused water is particularly important as the suitability of a given water source depends on the current salinity of the pond to be irrigated. To these ends, the proposed project will develop a wireless sensor network (SMART-PADDY) comprised of low-cost EC measurement nodes and an autonomous power supply based on energy harvesting, that will be capable of transmitting readings in real- time to a central server. This data will enable cultivators to effectively manage and protect of their paddy fields and greatly reduce flood water consumption.