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A low cost, low power soil moisture sensor

Researchers at the Indian Institute of Science, Bangalore in collaboration with IIT Bombay, have come up with a low cost, low power soil moisture sensor that can accurately determine the water content of soil.

Soil moisture plays a critical role in maintaining the overall balance of the Earth. It directly influences long-term climatic conditions like hydrological process and drought development. On much shorter time scales, it acts as a carrier of nutrients to plant's roots, and helps sustain life on Earth. In fact, in 2010, soil moisture was recognised as an Essential Climate Variable.

Almost half of India's workforce depend on agriculture and allied services like forestry and fishery. These sectors account for 13.7% of India's GDP, and have made India one of the largest exporter of farming products. Since the farm output is directly linked to moisture content in the soil, an easy to use soil moisture sensor is an essential tool for a country like India.

The most popular way of finding soil moisture is to measure its ability to store heat. The sensors based on the “heat pulse”have two challenges: being expensive and consuming a lot of power. The IISc–IIT Bombay research team has developed a soil moisture sensor that is both cheap and requires little power to run. Powered by a solar cell array, the sensor works for three days, non-stop.

"This was achieved with proper materials selection, geometry of the heater probe, and signal conditioning and amplification, and of course through a lot of hard work by my students, Nikhil Jorapur and Adhithi Raman”, says Prof G K Anathasuresh, Professor of Mechanical Engineering, Indian Institute of Science, Bangalore. He noted that electronic integration and interfacing with a small solar array was done by a partnering team from IIT-Bombay, led by Prof. Maryam Bhagini.

The researchers calibrated the sensor against white clay, whose properties are well known and documented, and tested it on red soil, commonly found in South India. The sensor can test different kinds of soil and accurately measure moisture content up to 30%, which is the above the saturation limit for most soils.

The new sensor designed by the team is currently undergoing field trials. It promises to be more affordable to our poor farmers and introduces 'smart farming' with the use of latest technology.

Author information:

G.K. Ananthasuresh is a Professor at the Department of Mechanical Engineering, Indian Institute of Science, Bangalore, and Nikhil Jorapur is his student. Maryam Shojaei Baghini is a Professor in the Department of Electrical Engineering, Indian Institute of Technology- Bombay, Mumbai. Shahbaz Sarik and Jobish John are at IIT-Bombay, Mumbai. Vinay S. Palaparthy is at the Centre for Research in Nanotechnology and Science, Indian Institute of Technology-Bombay, Mumbai.

Contact: suresh@mecheng.iisc.ernet.in. Telephone: +91 (80) 2293 2334.

Link to paper: http://www.sciencedirect.com/science/article/pii/S0924424715300479

G.K