• By Vicky Boyd,
More than 250 rice producers, consultants and allied ag industry representatives packed tour trailers during the University of Arkansas’ recent rice field day at the Rice Research and Extension Center near Stuttgart.
Departing from the Rice Expo format, which included brief research center tours as well as activities for urban residents, this year’s rice field day focused more on the latest research and industry hot issues.
For example, Chris Henry, a water management engineer, discussed his work with fertilization of row rice, also known as furrow-irrigated rice. The practice, which involves planting rice in beds and furrow irrigating it much like corn or soybeans, may require a different fertility regime.
With conventionally flooded rice, the University of Arkansas recommends applying the bulk of nitrogen up front, then using a GreenSeeker handheld midseason to determine whether top dressing is necessary.
Because the furrow irrigation may move nitrogen or may increase volatilization, the system may require additional or differently timed nitrogen.
Henry also is studying conventionally tilled compared to no-till row rice plots as well as applying nitrogen as UAN through the irrigation water.
Grassiest crop in years
This season is the grassiest that even long-time growers and consultants can remember. University of Arkansas weed science professor Jason Norsworthy blamed it on dry, hot spring conditions, which complicated getting pre-emerge herbicides activated. Once growers got behind on grass control, they had a difficult time gaining the upper hand.
Barnyardgrass was the biggest culprit, with some growers spending more than $150 per acre on herbicides to try to control the weed.
“And they still have some weedy fields,” he said. “This is probably the grassiest crop of rice I’ve seen in Arkansas in many, many years.
“In hindsight, I think we pulled away from coming back in early enough with early post (products) to try to overlap residuals.”
Norsworthy said he doesn’t think growers are using enough Prowl or Bolero herbicides, the only two products to which barnyardgrass is not yet resistant.
He also is working with colleagues to determine the factors behind control issues and crop injury associated with the new herbicide from Corteva, Loyant with Rinskor active.
“Medium-grain definitely has some sensitivity,” Norsworthy said. “Overall I think hybrids are slightly more sensitive than medium grain, and we can pick up some delays in heading as a result of the injury we have developed on rice.”
Tips on using the GreenSeeker
An increasing number of growers and consultants this season used the GreenSeeker handheld to determine whether their crop has enough midseason nitrogen or needs an additional top dressing.
Trent Roberts, an associate professor of soil fertility/soil testing, said the NDVI readings produced by the handheld are different from those generated from NDVI (normalized difference vegetation index) maps produced from satellite or aerial imagery.
The GreenSeeker produces its own light source. A sensor within the unit measures the amount of a specific lightwave spectrum that is reflected off the rice. Environmental conditions won’t affect the readings, and the handheld can be used on sunny or cloudy days or at different times during the day without affecting results.
NDVI maps from aerial imaging use near-infrared cameras to measure the amount of specific light wavelenths reflected by the crop. So clouds or time of day can affect the results.
Although the GreenSeeker readings are not affected by light sources, they can be affected by dew on the leaves, Roberts said. Heavy dews will absorb more light, skewing the results.
Thin stands also can affect the results, prompting readings that more nitrogen is needed when it may not be the case.
Don’t bug me
Newer varieties and hybrids that tiller more may produce higher yields but they also create tiring conditions for scouting fields for rice stink bug.
Aaron Cato, a graduate student in entomology, has been working to revise rice stink bug sweep methods to ensure more uniform results while reducing the energy needed to scout a field.
“Everybody sweeps differently,” he said.
Instead of digging deep into the canopy as you would in soybeans for stink bugs, Cato said the sweep net should be held at head level.
Sweeping too low in the rice canopy causes the stink bug to fly, resulting in a lower-than-actual count.
You don’t need to make a 180-degree circle with each sweep either. Instead about a 6-foot sweep is fine.
The head of the net should be tilted slightly back so when you hit the head, the pest falls into the net. In addition, take one to two steps between each sweep so you’re not sampling the same rice plants.
In each field, the university recommends 10 sets of sweeps at 10 different locations in the field. These should be 50 to 100 feet in the field and not on the edge, where stink bug numbers may be higher.
Current University of Arkansas recommendations call for treatment if you pick up 5 or more stink bugs per 10 sweeps during the first two weeks of heading until milk or the beginning of soft dough stage. Heading is defined when 75 percent of the plants have headed across the field.
After the first two weeks, then the threshold increases to 10 rice stink bugs per 10 sweeps.
Cato also cautioned against tankmixing a rice stink bug treatment with a fungicide spray if you haven’t yet reached stink bug thresholds. He pointed to Texas and Louisiana, where rice stink bugs have developed resistance to pyrethroids, the go-to treatment for the pest.