It’s OK to let the rice flood down

• By Drew Gholson and Dan Roach •

Alternate wetting and drying is a water-saving technology that farmers can use to reduce the amount of irrigation water used in rice fields without any yield penalty.

In AWD, farmers allow the flood water to recede to a “muddy” state before re-flooding the field. The number of days of non-flooded soil between irrigations can vary from one day to more than five days, depending on soil type, weather and crop growth stage. This process lowers the total time pumping in addition to capturing rainfall.

Since 2014, the Mississippi State University irrigation team has implemented 18 farmer on-farm AWD irrigation trials. Each farmer agreed to irrigate his field conventionally through levee gates, via multiple inlet, and an additional multiple inlet field using  AWD.

The farmer initiated irrigation on the conventional and multiple inlet fields, while the MSU researcher scheduled irrigation on the multiple inlet AWD field. The MSU researcher allowed the field to drain to a muddy state using a Pani pipe to assist his observations before making the decision to irrigate.

Having the Pani pipe installed in the field allowed the researcher to monitor the water level to 4 inches below the soil surface. Weather forecasts were also used in the decision making process. The conventional and multiple inlet fields held “at capacity” or a 4-inch flood permitted rainfall to become runoff. Using AWD allowed for the capture of rainfall.

Results from the 2014-2016 trails are summarized below. Included are the yield and water use data for each grower location as well as an average of all data. The fields irrigated with conventional levee gates had an average water use of 34.3 acre-inches.

AWD results

The use of multiple inlet reduced water use by 5.6 acre-inches with an average of 28.7 acre-inches used. Through the use of AWD, we were able to further reduce water use by an average of 10.9 acre-inches over the conventional fields.

This resulted in an average water savings of $30 per acre over the conventional irrigated field. Our on-farm data indicates that multiple-inlet AWD maintains yield potential of conventionally irrigated systems while significantly reducing water use.

These results should give farmers to confidence in “taking it down” and the water saving best management practices that farmers can implement on their individual farms. If you would like to discuss AWD or need assistance, Dr. Gholson can be reached at 979-255-7018.

Dr. Drew Gholson is an irrigation specialist at the MSU Delta Research and Extension Center and the Mississippi River Valley Alluvial Aquifer Water Center. He may be reached at drew.gholson@msstate.edu. Dan Roach is an MSU Extension associate.