Looking for a New Way to Farm Rice
Home to roughly half of the U.S. rice crop, Arkansas depends on its fields for food and jobs. But rice agriculture comes with some potentially harmful, yet solvable, environmental consequences. The crop uses large amounts of water in flooding the fields during hot summers conducive to evaporation, generating unsustainable withdrawals from the region’s great aquifers. The swampy conditions generated by flooded rice paddies also activate methane-creating microbes. Worldwide, rice production is responsible for 10 percent of the anthropogenic contribution of methane into the atmosphere. Since methane is 25 to30 percent more heat-trapping than carbon dioxide, reducing its emissions to the atmosphere is of great importance.
Benjamin Runkle and his research team are working on this problem. This summer, Runkle, an assistant professor of biological and agricultural engineering, and his students will spend several days in the field in eastern Arkansas, where they have set up instruments to measure water use, soil and water chemistry and methane production.
This is the first of a series of field notes submitted by Runkle and his research team.
Visiting a research field site is a commitment to a day filled with challenges, accomplishments, and surprises. My research group – numbering six for the summer – wakes up early for the three and a half hour drive to eastern Arkansas, home of our research instrumentation on a rice farm.
My research focuses on water-saving strategies that rice farmers can use to reduce water use and disrupt methane production. Rather than continuously flooding the field, the farmers can use a technique called “alternate wetting and drying” which allows the flood to fully evaporate or run off before the next application of water. This method has been shown to cut methane production in half, while increasing water use efficiency by over 50 percent, so it offers considerable advantages.
In our field visits we perform a number of tasks. Since we’re a young group – I started my position at the University of Arkansas in August 2014 – a lot of our tasks involve installing new monitoring instruments. We place meteorological sensors on a tripod at the field’s edge, soil sensors within the paddy’s clay, and water quality sensors within the flooded waters. These are all connected to dataloggers that record measurements of field conditions at rates ranging from 20 times per second (for quickly changing meteorological terms) to every half hour (for slow-changing soil conditions). Together we aim to generate a stronger understanding of the links between farm water use, soil and water biogeochemistry, and methane production. This integration of different components will help models predict how different fields respond to changing environmental conditions – both in irrigation decision-making and in changes to weather and climate patterns.
Setting up instrumentation can be fun and exciting – each device is a challenge to overcome! How does this one log, how is it wired? Where can we put it so that it doesn’t interfere with one of the other sensors or with the farm’s operations? When we get to the field we’ll often discover some small problem with one of the sensors already in place – perhaps a bird dropped a gift onto it; perhaps a wire became loose in the last storm. So our day is full of moments of installing, fixing, tinkering, and also downloading from a logger the fruits of our past work. This data is then critically examined back in the office to prepare questions and tinkering ideas for the next week’s field trip.