Crop irrigation comes in many forms; and where water is plentiful, flood irrigation still has a place. Yet producers using this approach are seeking improved efficiency, too. Chris Henry, associate professor and water management engineer, University of Arkansas, shared information on work he’s done with poly pipe irrigation to improve efficiency and returns in Mid-South rice.
Henry points out that rising demand to meet global food needs will come in tandem with the demand to cut water use. “We looked at what we would do to be sustainable,” he said. “Based on the need to cut water use, we would have to stop irrigating soybeans; we would have to cut our water use in half.” Henry spoke at the recent Irrigation Association annual meeting in Long Beach, Calif., and discussed irrigation in the South, but his conversation about poly pipe offers insight for any farmer looking at using that tool in a flood situation.
The Mid-South region of the country has plenty of rainfall, but there’s a timing issue. In the heat of midsummer, the rains stop. That hot weather can parch crops, so irrigation is required to achieve good yields. And there’s available surface and groundwater to supply thirsty crops.
Growers in the region have been turning to poly pipe to deliver water to fields, and that technology is getting more precise, too. A tool more farmers are adopting is the use of a computer aid to determine hole size along the length of the pipe.
Henry noted that in his work, the poly pipe supplier he uses has come up with a computer program to help. “You draw out your field, put in pipe size information, your flow rate, and the system measures the row length and proportions water flow,” he explained.
The system can adjust for elevation changes, too. The key is making sure hole sizes are right across the length of the pipe. “We’ve found that small increases in elevation can be a challenge,” he noted.
Punching holes in new pipe requires some precision. The system Henry uses, from Delta Plastics, is called Pipe Planner. Once the information is provided, the system kicks out a spreadsheet you use when putting holes in the pipe. “If the holes are too small, you can burst your pipe; and if the holes are too big, your distribution uniformity will be way off,” he explained.
Benefits of computers
How might this computer hole system work best? Consider a field where row length starts shorter at one end and continues to lengthen across the field. If hole size in the poly pipe was the same across the length, the short rows would be flooded out early, and water for longer rows would not be evenly distributed. With the computer plan, water from the smaller holes leading to shorter rows would slow the distribution of water. This creates a more even flow of water across odd-shaped fields.
Henry found in researching farmers that about 40% of farmers said they used computerized hole selection, while 58% said they didn’t. The rest didn’t know.
There is a payoff for using that approach for pipe. Henry found that in his irrigation water management trials, where there were matched fields, he compared water use for farmers doing what they always do and his approach with computerized hole placement and increased water use monitoring.
“In our work, everybody irrigated more than we did, with yields that were not statistically different between the fields,” Henry pointed out. “We were cutting water use by as much as 27% in those fields. Computerized hole selection fields cut water use 19%, and that’s significant.”
Henry said he was able to document 2.4 acre-inches of water savings in his irrigation water management fields using evapotranspiration (ET) and soil moisture sensors to manage water use. The rising requirement for water metering will drive farmers in flood areas to look for ways to better manage water use.
Perhaps it starts with how they punch holes in poly pipe.