Conventional flood and optimized AWD produced highest yields after two-year Mississippi State University trial.
By Bobby Golden
Producing rice in a “rowed-up” manner as other row crops such as corn, soybeans and cotton was a foreign concept just a few years ago. Row rice or furrow-irrigated rice was initially investigated by Mississippi State University researchers in the 1980s as an alternative to conventional flooded rice production.
Some of you may recall Dr. Joe Street and Dr. Ted Miller worked with Clarksdale’s Leon Bramlett to explore the agronomics of furrow-irrigated rice.
Bramlett wanted an alternate crop to raise on his traditional cotton farm. The idea of furrow-irrigated rice was begun in Mississippi. This was long before the introduction of new rice herbicides, such as Facet, Command, Newpath and Clearpath, and issues with weed control ultimately led to the abandonment of the concept.
Today, there is tremendous interest in growing furrow-irrigated rice compared to growing rice in a typical flooded environment.
In 2016, the MSU Irrigation Team, prompted by producer demand, started investigating furrow-irrigated rice. Graduate student Lee Atwill has completed two years of small-plot research at the Delta Research and Extension Center in Stoneville.
Putting row rice to the test
Atwill investigated both conventional and Clearfield herbicide systems using three rice cultivars — CL151, Rex and XL745. Six different rice irrigation treatments were also included:
• A continuous flood
• An optimized AWD (alternate wetting and drying) treatment allowing the flood to recede to 4 inches below the soil surface on the top while maintaining flood water on the bottom of the plots
• AWD but allowing the flood throughout the plot to recede 4 inches below the soil surface
• AWD but allowing the flood throughout the plot to recede 8 inches below the soil surface
• AWD but allowing the flood throughout the plot to recede 12 inches below the soil surface and
• AWD but allowing the flood throughout the plot to recede 16 inches below the soil surface.
Water levels in each paddy were monitored using a Pani pipe, and irrigations were triggered at each respective threshold.
Although individual herbicide treatments performed well in Atwill’s trial, additional scouting may be required for broadleaf weeds with row rice.
Nitrogen use investigated, too
Nitrogen management was also investigated using the different rice cultivars and irrigation treatments. The results suggest that high yields were achieved when nitrogen was applied using a three-way spilt of 50/25/25.
The other treatments of 100 percent pre-flood, two thirds/one third split, and a four-way split of 25 percent/25 percent/25 percent/25 percent all resulted in similar yield. All fertilizer was NBPT treated, and applications were made to wet soils with the exception of the initial pre-flood treatments.
Rice yields among irrigation treatments resulted in the continuous flood and optimized AWD treatments producing similar results.
All other irrigation plots were statistically similar, resulting in a 20-bushel yield decrease compared to continuous flood and optimized AWD. It should be noted that the optimized AWD allowed the water on the top of the plots to recede to 4 inches below the soil surface while maintaining flood water on the bottom of the plots.
The other row-rice irrigation treatments differ in that the entire plot was allowed to dry equally from top to bottom. These small-plot trial “worst-case” scenarios help explain the yield variation we have seen in the on-farm trial work.
Dr. Bobby Golden is an Extension agronomist at the Delta Research and Extension Center in Stoneville, Mississippi. He may be reached at firstname.lastname@example.org.