MSU research sheds light on row-rice yields

• By Bobby Golden and Dan Roach •

Producing rice in a “rowed-up” manner as other row crops such as corn, soybean and cotton, was a foreign concept just a couple of years ago. Row rice or furrow-irrigated rice was initially investigated by Mississippi State University researchers as an alternative to conventional flooded rice production in the 1980s.

Some of you may recall Drs. Joe Street and 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 began in Mississippi.

This was long before the introduction of the “new” rice herbicides 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.

Small-lot trials

In 2016, the MSU Irrigation team, due to 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. A summary of his research is presented below.

Atwill investigated both a conventional and the Clearfield herbicide system using three rice cultivars: CL151, Rex and XL745 (RiceTec). 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 while maintaining flood water on the bottom side of the plots, 4 inches below the soil surface, 8 inches below the soil surface, 12 inches below the soil surface, and 16”= inches below the soil surface.

pani pipe

Water levels were monitored with a Pani pipe — photos courtesy Mississippi State University

Water levels in each paddy were monitored using a Pani pipe and irrigations were triggered at each respective threshold. While individual herbicide treatments preformed well in Atwill’s trial, additional scouting may be required for broadleaf weed with implementing row rice.

Nitrogen management was also investigated using the different rice cultivars and irrigation treatments. The results suggest that when nitrogen is applied using a three-way spilt of 50/25/25, highest yields were achieved. The other treatments — 100 percent pre flood, two thirds/one third split and 25/25/25/25 — all resulted in the similar yield. All fertilizer (NBPT treated) applications were applied to wet soils except for 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 side of the plots to receded to 4 inches below the soil surface while maintaining flood water on the bottom side 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.

Data from on-farm trials help MSU researchers understand some of the yield perimeters associated with furrow-irrigated rice. If you ask experienced furrow-irrigated rice producers, one thing is clear. They recognize only a small, if any, yield reduction.

Digging deeper

MSU researchers, recognizing the significant yield reduction observed in small plot data compared to producer experience, began looking deeper into the on farm data for answers.

The two year furrow-irrigated rice small plot data suggest that a continuous flood irrigation and an optimized AWD (allowing the flood to recede to 4 inches below the soil surface while maintaining flood water on the bottom side of the plots) irrigation yield substantially better than allowing the soil to become dry.

When you think about what actually happens on the farm, each field of furrow-irrigated rice is actually three sub fields. As demonstrated by the example, the top one third is the driest, the middle is similar to the optimized AWD treatments (soupy wet but never dry) and the bottom one third resembles a continuous irrigated field.

row rice field yieldsThis yield map is from a furrow-irrigated field divided by a levee in the center of the field, making essentially two individual fields. Water was held by the levee as well as the flash board riser.

When you break down the yield in each sub section, the top of the field, the driest, yields were reduced by 12 percent. The center part of the field, the optimized AWD section (part that remains soupy) yields were reduced by 7 percent. The section on the bottom side of the field with a continuous flood yielded the highest.

The take-home from this analysis is: furrow-irrigated fields where producers keep the field moist and are holding a continuous flood on the bottom one third of the field can expect a yield reduction in the 8-10 bushel range. Producers where the grade of the field will not allow holding a continuous flood on the bottom side of the field can expect substantial yield losses in the 20-bushel range.

row rice vs conventional floodHere is the adjacent conventional levee yield map compared to the row rice field. In this comparison, the whole field average of the row rice field was equal to the conventional levee field. The adjacent conventional levee field was on 0.2 grade with levees every 100 feet, contributing to a lower field average. Fields with grades great than 0.2 can be a good fit for row rice.

Dr. Bobby Golden is an agronomist at the MSU Delta Research and Extension Center in Stoneville. He may be reached at BGolden@drec.msstate.edu. Dan Roach is an Extension research associate at the DREC. The article originally appeared on the Mississippi Crop Situation website.