A SMART irrigation sensor that gives plants only as much to drink as they
need can increase tomato yields by more than 40 per cent. The sensor has been
developed by Yehoshua Sharon and Ben-ami Bravdo at the Hebrew University of
Jerusalem鈥檚 faculty of agriculture in Rehovot, Israel.
The researchers say that their system not only increases the yield of crops,
but it also dramatically reduces water usage鈥攂y up to 60 per cent for some
crops.
At the heart of the system is an electronic sensor that clips onto a plant
leaf and measures its thickness to an accuracy of 1 micrometre. 鈥淎 leaf鈥檚
thickness is dependent on the amount of water in a plant,鈥� says Sharon. 鈥淎
healthy leaf is 60 per cent water.鈥� A thin leaf is a sure sign that the plant is
suffering stress because it is thirsty, and stress is bad for yields.
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The sensor consists of two plates, one fixed and the other spring-loaded,
which together grip the leaf. The moving plate is connected to a small
potentiometer that regulates the voltage in an electrical circuit. As the leaf鈥檚
thickness changes, the plate moves, causing a change in the voltage. This signal
is fed to a processor that adjusts the plant鈥檚 water supply.
Unlike conventional irrigation systems, which water crops periodically, the
Israeli system waters the plants continuously, but adjusts the flow to the
plants鈥� needs. 鈥淭he idea is to give the plant the proper amount of water at the
correct time, according to what the plant requires,鈥� says Sharon.
Field studies show the system increases the yields of several crops while
reducing consumption of water. Yields of grapefruit increased by 15 per cent
while needing 40 per cent less water. For peppers the yield rose 5 per cent
while water usage fell by 60 per cent. Tomato plants yielded 40 per cent more
fruit while consuming 35 per cent less water.
鈥淚t is an interesting idea,鈥� says John Sadler, a soil scientist at the US
government鈥檚 Agricultural Research Service in Florence, South Carolina. 鈥淥ther
researchers have measured stress by measuring a plant鈥檚 temperature or stem
thickness. But I haven鈥檛 heard of anyone doing irrigation at such a refined
level,鈥� he says.
But Sadler is a little surprised by the figures for water savings. 鈥淭hey
would depend on the technique you鈥檙e comparing these results with,鈥� he says.
Sharon says the savings are based on comparisons with the Israeli government鈥檚
recommendations for irrigating crops.
He admits that the system has to be very reliable if it is to be effective.
鈥淏ecause the plants are watered continuously they are more susceptible to sudden
changes in water supply,鈥� he says. 鈥淭his means our system has to operate very
谤别濒颈补产濒测.鈥�
The researchers have founded a company called LeafSen to sell the new
irrigation system, and they hope to start marketing it within the next few
months.
