The idea for seed-specific chemical placement of fungicides came from UT plant pathologist Melvin Newman, a scientist at the West Tennessee Experiment Station in Jackson.
Newman was concerned because in-furrow fungicides are often the first input left off cotton production programs when Tennessee growers are forced to cut costs. This happens even though the state’s disease losses are among the highest in the Cotton Belt.
Newman asked agricultural engineers at UT to determine the feasibility of an intermittent in-furrow applicator that could apply a liquid spray in the seed furrow in a 1-inch to 3-inch band rather than in a continuous band.
There are several factors which could make the technology feasible for Tennessee growers, according to UT research assistant John Hancock. Hancock demonstrated a prototype of the device during the Milan No-Till Field Day.
“Currently in-furrow fungicides are applied in a continuous band along the seed furrow,” he said. “The potential for savings are quite significant if fungicides are not sprayed in the part of the furrow between seeds.”
Material applied between seeds “really isn’t needed and doesn’t have a benefit,” Hancock noted. “Soil fungicides create a protection zone around the seed. As long as the seed grows through soil that has been treated, it will be protected.”
In addition, “The recent introduction of transgenic seeds, while a big benefit for growers, has increased seeding costs significantly” and many growers are lowering seedling rates to save money.
“We used to plant six to seven seeds per foot, knowing that seedling disease would take out about half of them,” Hancock said. “When you cut your seeding rate back to two to three seeds per foot, as we’ve done with transgenic varieties, if disease takes half of those, you’re down to less than a seed per foot.”
The result is an increased need to protect the seed with fungicides as well as potential savings in fungicide applications, according to Hancock.
Hancock explained that with six to seven seeds per foot “ there is very little opportunity to gain savings from not spraying between seeds since they’re so close together.
“When you cut that back to four seeds per foot, you can reduce your material sprayed by half (depending on the length of the band). When you’re down to two seeds per foot, you can reduce your chemical almost 75 percent.”
Researchers had little problem devising a prototype that could sense the seed traveling down the seed tube and then track it into the furrow. Devising something that could apply a quick burst of liquid fungicide very precisely at relatively high planting speeds, well, that was a bit of a challenge.
“When you figure that farmers are planting at 4 to 8 mph and with three to six seeds per foot, you’re planting 20 seeds to 50 seeds per second,” Hancock said. “That means our valve has to come on and off 50 times a second. So we put a valve on the prototype model that opens and closes in 1/1000 of a second.”
Tests performed on a farm in Jackson, Tenn., showed no statistical differences between intermittent seed-specific applications of a liquid fungicide and a continuous band application, according to Hancock. “In fact, we saw the highest stand count in the intermittent areas.”
A check plot had only 10 seedlings per 60 feet of row, for a final stand count of less than one plant per 5 feet. All the plots were inoculated with pathogens.
The researchers then kicked up the test to see if the prototype could place the band on top of the seed under normal field conditions. They upped speed to 4 to 6 mph, increased the seeding rate and tried five band lengths.
The study showed that a 1-inch band hit the seed 75 percent of the time at 4 mph. At 3-seeds per foot, this equated to chemical savings of 75 percent.
“But the experts we talked to said we need to hit at least 90 percent of the seeds,” Hancock said. “We achieved this by going to a 2-inch band. At three seeds per foot “you still save 50 percent of your material.”
The unit is still several years from the market. It will be designed to retrofit on existing planters at around $200 per row.