Agronomist looks for balance between lower inputs and better yields

Frances Gould  |  10/24/2013 10:33:48 PM

Louisiana chefs who use the Jazzman rice variety developed by the LSU AgCenter attended the Rice Research Station Field Day July 1. Dr. Xueyan Sha, LSU AgCenter rice breeder, far left, and Dr. Steve Linscombe, AgCenter regional director and station director, seventh from the right, are pictured with the chefs.

What is the lowest seeding rate for Clearfield rice that a farmer can use to obtain optimum yield in a drill-seeded system?

That’s what LSU AgCenter agronomist Dr. Dustin Harrell is studying in a two-year project.

Harrell said using lower seeding rates requires more intense crop management. That means starting the season with an even stand, using the correct amount of fertilizer at the right time, maintaining proper soil moisture and staying on top of weed control.

To make all of the trials uniform, Harrell said he measures based on the amount of seed per square foot rather than the equivalence of pounds of seed per acre – because varieties differ in seed weight. He said the data on a variety basis can be extrapolated to pounds of seed per acre.

The LSU AgCenter currently recommends 60-90 pounds of seed per acre with a target plant population of 10-15 plants per square foot for drilled rice.

But Harrell said the preliminary information from 2010, which was the first year of the study, indicates optimum yield for most varieties was achieved when a minimum stand of 6-8 plants per square foot was obtained.

Seeding rates as low as 22 pounds per acre (CL131 and CL151) and 24 pounds per acre (CL181 and CL261) were needed to achieve the optimum stand. Other varieties needed 35 pounds per acre (CL111) and 39 pounds per acre (CL142).

In most cases, Harrell said, results from the first year of the study showed the conventional Clearfield varieties could be grown using seeding rates currently being used in commercial hybrid rice production. He did warn, however, that these results are only from one year of data using small-plot research, which was precision planted with a cone planter and intensely managed.

"We do not recommend producers use these low seeding rates," Harrell stressed. "But with similar research in future years, we might be able to lower our seeding rate recommendations."

Harrell said lower seeding rates result in increased tillers and more panicles on a per plant basis. Seeding rates less than 60 pounds per acre also delayed time to 50 percent heading by up to five days at the lowest seeding rate. A higher plant population usually results in taller plants with fewer tillers and an earlier maturity date.

The LSU AgCenter agronomist explained the study was conducted with the realization that farmers already have been reducing the amount of seed they use for Clearfield varieties and hybrids while still obtaining good yields.

Harrell also is looking into the seeding rates needed to achieve optimum   yields in the ratoon crop, which he said will probably not mirror the results of the first crop. And he said farmers likely to grow a second crop may want to continue with the 60-to- 90-pounds-per-acre seeding rate.

"A ratoon crop probably does better with more plants and fewer tillers," Harrell said. The time and effort required for the project are best demonstrated by the numbers. Nine seeding rates, ranging from 10 to 110 pounds per acre, were used with six Clearfield varieties (CL111, CL131, CL151, CL142, CL181 and CL261) using two different tillage systems (conventional and fall stale seedbed), all with four replications. All total, Harrell said, 432 plots were grown for this study alone.

Before harvest, plant height and lodging potential were measured.

In addition, after harvesting the rice, a considerable amount of work will have to be done that will require several additional months of tedious work. Yield components such as the number of panicles, the number of filled grains per panicle, panicle weight, average seed weight and milling quality all will be determined.

"That’s the value of having good research associates like Ron Regan, James Leonards and Jacob Fluitt," Harrell said.

All of the data will be available at the winter meetings held throughout the state’s rice-growing regions in January.  

Checkoff funds for this
project in 2010: $125,000

(This article was published in the 2011 Louisiana Rice Research Board Annual Report.)

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