Rice Farming

What goes around, comes around, even in rice planting systems.

Drill-seeding was a common practice during the early years of California rice production. Without synthetic herbicides, however, barnyardgrass infestations grew so severe that many growers had to find a new way to plant or risk going out of business. That led to water-seeding, which now is the standard practice.

But once again, weed-control concerns have growers and researchers taking a second look at drill-seeding.
“In the late 1990s, pesticide restrictions on rice were becoming stricter,” says Eric Tenhunfeld of Tenhunfeld Ag-Ventures Inc. in Woodland, Calif. “Our operation was looking for new alternatives. In about 2000, we began drilling dry seed and irrigating to establish the stand.

We had discovered there were several chemicals registered for drill-seeded rice that were more environmentally friendly and much more cost-effective.”

Herbicide resistance has been another key concern, says Dr. Albert J. Fischer, associate professor of weed ecophysiology in rice systems at the University of California, Davis. “Water-seeding has over the years selected for a specific set of weeds that are particularly adapted to this anaerobic system,” he says.

These include watergrasses (Echinochloa phylolopogon and E. oryzoides), ricefield bulrush (Schoenoplectus mucronatus), smallflower umbrellasedge (Cyperus difformis), California arrowhead (Saggittaria montevidensis) and redstem (Ammannia spp).

“These weeds have developed resistance to many herbicides,” Fischer says. “The watergrasses are really susceptible only to propanil, and the broadleaf and sedge weeds have evolved resistance to bensulfuron methyl (Londax). Resistant biotypes of these weeds are distributed throughout the rice growing areas of California.”

Rice farmers should not expect new chemistry to be available any time soon.

“The registration of new compounds with modes of action different to what is currently available that would be able to control resistant watergrasses, probably our most serious weeds, has virtually come to a halt,” Fischer says. “Molinate (Ordram) applied into the water shortly after seeding was the pillar for watergrass control in water-seeded rice. This herbicide will be phased out within the next five years due to regulatory restrictions and fails to control the widely dispersed resistant watergrass biotypes.”

Viable alternative?
Most effective new foliar herbicides require that the water be lowered or completely drained to achieve foliar contact with small emerging weeds, which is why drill-seeding is attracting renewed interest.

“Essentially there are two advantages,” Fischer says. “First of all, changing from an anaerobic to an aerobic seedbed provides a crop-establishment environment that is less favorable to the early establishment of the aquatic weeds that predominate after many years of water-seeding. This results in a shift in weed populations that may facilitate the control of the resistant weed biotypes.

“Secondly, dry- or drill-seeded rice would allow for the use of herbicides that cannot be used in water-seeded rice, such as pendimethalin (Prowl) or glyphosate (Roundup) in conjunction with a stale-seedbed technique. These herbicides can control resistant weed biotypes.”

These compounds require a different approach, he says.

“Certain herbicides that can be applied into the water early in the season have water-holding restrictions, and fields cannot be drained for about a month after herbicide application to prevent river water contamination,” he says. “Often, farms need to drain earlier than that to facilitate rice establishment under cold, windy or stressful conditions, and the required water holding period interferes with this practice.

“Dry or drill-seeding rice would allow the use of different chemicals to control resistant weed biotypes; these herbicides cannot be used in water-seeded rice.”

Real world experience
Of course, there are tradeoffs to every advantage, as Tenhunfeld discovered.

“We have experimented with drill-seeded rice for four years,” he says. “Our first experience was in about the early 1980s. The purpose was to attempt to grow rice without pesticides. We planted the rice 2 inches deep, and the weeds begin in the top 1 inch; thus, weeds could be cultivated out prior to seedling emergence. They would to a given degree, but the value added didn’t develop at the time.”

The results were mixed
“On occasions, we were able to achieve a good stand with excellent weed control,” he says. “But in most cases, stands were erratic. Weed control was good with few exceptions. With the decline in the ability to obtain consistent stands and yields, we could not continue to afford the economic difference in the two methods.”

Researchers are looking at ways to work out the bugs. Fischer and Extension agronomist Jim Hill are launching a four-year study at the Rice Experiment Station in Biggs, Calif. They will compare five systems—water-seeding, drill-seeding and combinations of those two with stale seedbed conditions.

“This aims at finding alternatives that would provide some of the relevant benefits of crop rotations in a crop that can seldom be rotated,” Fischer says. “We will be monitoring the effect of these alternatives on weed seedling recruitment and soil seedbank. Concomitantly, we will develop fertilization schemes and herbicide management suitable for these systems. This activity will be paralleled by on-farm experimentation and demonstration.”

Both Eric Tenhunfeld and Fischer encourage growers to evaluate direct-seeding in their own conditions, even if only for a year or two to get a handle on resistant species.

“I have not totally ruled out using this method,” Tenhunfeld says. “One should consider the ability to manage water in each field and isolate flooding to specific locations within a field.”

Also consider accessibility to quick flooding and drainage, soil type, pesticide regulations and the cost of water, rent and inputs, he says. Fischer reminds farmers to do their homework.

“First of all, become very acquainted with the techniques for doing so, seeking to adapt a procedure that is suitable to your soil type and irrigation conditions,” he says. “Secondly, modify the fertilization scheme to conform to that of dry- or drill-seeded rice. Then adapt your irrigation system to flush irrigated rice for emergence and establishment until a permanent flood can be established.

“Follow recommendation for herbicide use in such systems. Be prepared to face a stronger pressure of weeds like sprangletop, barnyardgrass and, in some cases, smallflower umbrellasedge.”

Also be on the lookout for new problems.

“Although red rice has not yet become a problem in California, largely due to the water-seeding system and the use of certified seed, this weed may find favorable conditions in a continuous dry-seeding system,“ Fischer says.

Perhaps the best advice is to move ahead slowly, keeping in mind that California farmers have made drill-seeding work before.

For questions or comments about this article, contact Rice Farming editor Vicky Boyd at (209) 571-0414 or vlboyd@att.net.

What goes around, comes around Old drill-seeding practice may help growers control new herbicide-resistant weeds
By Alan Goforth
What goes around, comes around, even in rice planting systems. Drill-seeding was a common practice during the early years of California rice production. Without synthetic herbicides, however, barnyardgrass infestations grew so severe that many growers had to find a new way to plant or risk going out of business. That led to water-seeding, which now is the standard practice. But once again, weed-control concerns have growers and researchers taking a second look at drill-seeding. “In the late 1990s, pesticide restrictions on rice were becoming stricter,” says Eric Tenhunfeld of Tenhunfeld Ag-Ventures Inc. in Woodland, Calif. “Our operation was looking for new alternatives. In about 2000, we began drilling dry seed and irrigating to establish the stand. We had discovered there were several chemicals registered for drill-seeded rice that were more environmentally friendly and much more cost-effective.” Herbicide resistance has been another key concern, says Dr. Albert J. Fischer, associate professor of weed ecophysiology in rice systems at the University of California, Davis. “Water-seeding has over the years selected for a specific set of weeds that are particularly adapted to this anaerobic system,” he says. These include watergrasses (Echinochloa phylolopogon and E. oryzoides), ricefield bulrush (Schoenoplectus mucronatus), smallflower umbrellasedge (Cyperus difformis), California arrowhead (Saggittaria montevidensis) and redstem (Ammannia spp). “These weeds have developed resistance to many herbicides,” Fischer says. “The watergrasses are really susceptible only to propanil, and the broadleaf and sedge weeds have evolved resistance to bensulfuron methyl (Londax). Resistant biotypes of these weeds are distributed throughout the rice growing areas of California.” Rice farmers should not expect new chemistry to be available any time soon. “The registration of new compounds with modes of action different to what is currently available that would be able to control resistant watergrasses, probably our most serious weeds, has virtually come to a halt,” Fischer says. “Molinate (Ordram) applied into the water shortly after seeding was the pillar for watergrass control in water-seeded rice. This herbicide will be phased out within the next five years due to regulatory restrictions and fails to control the widely dispersed resistant watergrass biotypes.” Viable alternative? Most effective new foliar herbicides require that the water be lowered or completely drained to achieve foliar contact with small emerging weeds, which is why drill-seeding is attracting renewed interest. “Essentially there are two advantages,” Fischer says. “First of all, changing from an anaerobic to an aerobic seedbed provides a crop-establishment environment that is less favorable to the early establishment of the aquatic weeds that predominate after many years of water-seeding. This results in a shift in weed populations that may facilitate the control of the resistant weed biotypes. “Secondly, dry- or drill-seeded rice would allow for the use of herbicides that cannot be used in water-seeded rice, such as pendimethalin (Prowl) or glyphosate (Roundup) in conjunction with a stale-seedbed technique. These herbicides can control resistant weed biotypes.” These compounds require a different approach, he says. “Certain herbicides that can be applied into the water early in the season have water-holding restrictions, and fields cannot be drained for about a month after herbicide application to prevent river water contamination,” he says. “Often, farms need to drain earlier than that to facilitate rice establishment under cold, windy or stressful conditions, and the required water holding period interferes with this practice. “Dry or drill-seeding rice would allow the use of different chemicals to control resistant weed biotypes; these herbicides cannot be used in water-seeded rice.” Real world experience Of course, there are tradeoffs to every advantage, as Tenhunfeld discovered. “We have experimented with drill-seeded rice for four years,” he says. “Our first experience was in about the early 1980s. The purpose was to attempt to grow rice without pesticides. We planted the rice 2 inches deep, and the weeds begin in the top 1 inch; thus, weeds could be cultivated out prior to seedling emergence. They would to a given degree, but the value added didn’t develop at the time.” The results were mixed “On occasions, we were able to achieve a good stand with excellent weed control,” he says. “But in most cases, stands were erratic. Weed control was good with few exceptions. With the decline in the ability to obtain consistent stands and yields, we could not continue to afford the economic difference in the two methods.” Researchers are looking at ways to work out the bugs. Fischer and Extension agronomist Jim Hill are launching a four-year study at the Rice Experiment Station in Biggs, Calif. They will compare five systems—water-seeding, drill-seeding and combinations of those two with stale seedbed conditions. “This aims at finding alternatives that would provide some of the relevant benefits of crop rotations in a crop that can seldom be rotated,” Fischer says. “We will be monitoring the effect of these alternatives on weed seedling recruitment and soil seedbank. Concomitantly, we will develop fertilization schemes and herbicide management suitable for these systems. This activity will be paralleled by on-farm experimentation and demonstration.” Both Eric Tenhunfeld and Fischer encourage growers to evaluate direct-seeding in their own conditions, even if only for a year or two to get a handle on resistant species. “I have not totally ruled out using this method,” Tenhunfeld says. “One should consider the ability to manage water in each field and isolate flooding to specific locations within a field.” Also consider accessibility to quick flooding and drainage, soil type, pesticide regulations and the cost of water, rent and inputs, he says. Fischer reminds farmers to do their homework. “First of all, become very acquainted with the techniques for doing so, seeking to adapt a procedure that is suitable to your soil type and irrigation conditions,” he says. “Secondly, modify the fertilization scheme to conform to that of dry- or drill-seeded rice. Then adapt your irrigation system to flush irrigated rice for emergence and establishment until a permanent flood can be established. “Follow recommendation for herbicide use in such systems. Be prepared to face a stronger pressure of weeds like sprangletop, barnyardgrass and, in some cases, smallflower umbrellasedge.” Also be on the lookout for new problems. “Although red rice has not yet become a problem in California, largely due to the water-seeding system and the use of certified seed, this weed may find favorable conditions in a continuous dry-seeding system,“ Fischer says. Perhaps the best advice is to move ahead slowly, keeping in mind that California farmers have made drill-seeding work before. For questions or comments about this article, contact Rice Farming editor Vicky Boyd at (209) 571-0414 or vlboyd@att.net.
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