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Rice scientist says: Rice growers can save on fertilizers, herbicides

It's no secret that Mid-South farmers are considering planting fewer acres of rice and more acres of cotton and soybeans due to concerns about higher diesel and fertilizer prices in 2006.

There's not much growers can do about the costs of those inputs — unless they happen to strike oil on the back 40 — but there are steps they can take to make more efficient use of fertilizer and fuel if they decide to stay with rice this year.

“We don't see many opportunities for you to save $50 to $60, but there will be times when you can have $15 to $20 here and there that may add up,” says Tim Walker, assistant research professor with the Delta Research and Extension Center at Stoneville, Miss.

Walker, a soil scientist who conducts most of the rice fertility research at Stoneville, says growers may be able to get more bang for their fertilizer dollar by applying nitrogen sooner in the season rather than later.

He, Extension rice specialist Nathan Buehring, who is also based at Stoneville, and Joseph Massey, associate professor, plant and soil sciences at Mississippi State University, talked about 2006 rice production issues at the 33rd annual Delta Ag Expo in Cleveland, Miss.

In the last two years, researchers at Stoneville have changed their approach to rice fertility studies to try to “show you where you may be making money with fertilizer applications and where you may not be,” according to Walker.

The scientists applied 90, 120, 150 and 180 pounds of nitrogen preflood combined with mid-season applications of zero, 30, 60 and 90 pounds of nitrogen. The study was conducted on a Sharkey clay soil in 2004 and 2005 and a Forestdale silt loam in 2005 and a Dundee silt loam in 2004.

“For Cheniere on clay soils, we saw yield increases with up to about 150 pounds applied preflood with no mid-season nitrogen before we started to flatten off,” he said. “So for Cheniere, Pace, Wells and others, it appears that on those clay soils we're going to set or maximize yields with our preflood rate in that 120- to 150-pound range.”

Walker said researchers have observed a slight increase in yields with the mid-season applications, “but not nearly as much as when we set that yield with the preflood rate.”

On Cheniere, for example, test plot yields averaged 8,200 pounds per acre with 150 pounds of nitrogen preflood and no mid-season application. Adding 60 pounds of N mid-season increased the yield average to about 8,350 pounds.

“With 150 pounds we're talking about 3 bushels of rice,” says Walker. “At $3 rice, that's only $9. If we increase our rice prices, it might pencil out. But with $300-per-ton urea you really have to look at the economics of putting a lot of fertilizer out at mid-season.”

With Pace, a variety released by MSU, researchers increased yields by 300 to 400 pounds with 60 pounds of mid-season nitrogen above the 150-pound preflood rate.

“You have to look at each variety individually and make a decision,” Walker says. “But we're still not seeing much of an increase with mid-season applications until we get to the 90-pound preflood rate. And, even then, 90 pounds of mid-season nitrogen just isn't paying for itself.”

Silt loam soils, or those with a cation exchange capacity of 15 to 20, are a different matter when it comes to releasing nitrogen, Walker notes.

The researchers saw yield increases up to the 120-pound rate of nitrogen applied preflood with silt loam soils, but once they got to 120 to 150 pounds preflood and added fertilizer at mid-season, yields started to decline.

“On some of our zero nitrogen plots on silt loam soils, we've had varieties that are cutting 4,000, 5,000 and sometimes 6,000 pounds of rice with no nitrogen,” Walker said. “On the clay soils, they're cutting 2,500 to 3,000 pounds. Our silt loam soils are just providing a lot more nitrogen for the plant.

“If you're on a farm that has predominantly silt loam soils, you can save a lot of money on nitrogen if you've been fertilizing them like you have the clays. If the soils are mixed, you may want to fertilize them individually based on soil type.”

The bottom line?

The highest yields for clay soils were achieved when preflood N rates were in the 120- to 150-pound range. “We do need some mid-season nitrogen on these clay soils,” he notes. “But seldom did we see an economic yield response when we went over 60 pounds.

“On silt loam soils, let's back off 30 pounds. I feel real comfortable with this as long as we're managing water. We can't throw it out there on the ground and not flood it up for two weeks. But, as long as we're putting nitrogen out on the ground and coming behind it with a flood, we can reduce our nitrogen by about 30 pounds on these light soils.”

The exception may be for RiceTec's hybrids. “When you see those heads begin to pop out on the hybrids, fly on 100 pounds of urea,” Walker said. “It will increase the milling by up to 4 to 5 points and, most of the time, will increase your yields as well.”

The much-anticipated higher costs of nitrogen fertilizers aren't the only consideration for growers as they plan for 2006, according to Walker and Buehring.

“When you fly on 46 pounds of nitrogen or 100 pounds of urea, it will cost you $20 an acre,” says Walker. “That's with $300-per-ton urea. I'm hearing urea may be higher than that in 2006, maybe as high as $330 per ton.”

Growers can also save money on ground applications of herbicides, Buehring notes. With ground applications of herbicides running a little more than $1 per acre and aerial spraying around $5 per acre, that's $4 per application. Again, it adds up.

“The sooner you get a herbicide out, the better the control,” he said. “Early season grass control is control. When you have grass in the field, you lose nitrogen because the grass is taking it up.”

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