Late for a very
important date?

Take steps to manage yield loss in late-planted rice
 

Planting rice beyond optimum dates can severely impact yield, though the effect will vary depending on region, conditions during the growing season, variety and other considerations. Planting dates are sometimes beyond your control—as a result of wet weather—or a business decision based on market factors. In either case, there are steps you can take to minimize the impact late planting will have on harvested yield.
Variety selection, fertilizer and water management, and how insects and diseases are managed may have to be altered, depending on how late the crop is planted and the region.

Way out West
In California, growers during the 2003 season were hit by a deluge of wet weather in the spring that delayed planting by at least three weeks. Still, Jack Williams, farm advisor emeritus with the University of California Cooperative Extension, says growers did reasonably well given the late start. He credits a large part to management efforts that helped get the crop in quickly and harvested before cool temperatures and fall rains could do much damage to yield.

UCCE provides conservative guidelines for targeted planting dates of between April 20 and May 25, depending on variety, and growers use them in addition to their own local experience, conditions and tolerance to risk. Williams says many of the assumptions and recommendations about planting dates have changed in recent years as newer varieties have come on the market that are more tolerant to planting-related problems.

“The whole idea of what we can and can’t do has changed with improved varieties and grower management compared to the time when California had few varieties with relatively narrow planting date requirements,” he says.

The biggest risk to yield in California comes from cooler temperatures throughout the season and particularly during pollen development, which can lead to higher rates of blanking and limit the crop’s ability to ripen. Williams says, however, that growers in California are able to manage against significant yield impacts through variety selection and cultural practices. As a result, many growers survived the late plantings last season with surprisingly good returns.

“Yields were down a bit last year, but not as much as we thought it might be,” says Williams, who retired from Extension in Sutter and Yuba counties late last season. “A particularly warm July helped offset the late planting. We had predicted yield would be about 75 sacks, but I think it came in closer to the higher 70s, which is not far off of usual. Many growers were probably satisfied with that average.” (A sack is 100 pounds or a hundredweight.)

Some of those growers opted to switch from their standard medium-grain varieties, such as M-202 and M-205, to very early-maturating varieties, including M-104 and its predecessor, M-103, Williams says. Those varieties mature seven to 10 days earlier.

If you find yourself in a delayed-planting situation, Williams says you can help speed the planting process by reducing the number of tillage operations prior to planting and skipping land planing if fields are in relatively good shape.

You can also switch from a ground application of liquid ammonia-based nitrogen fertilizer to an aerial application of granular urea to shave a few days. It is important to allow time between tillage operations for drying to occur. This helps reduce weed germination and also promotes soil fertility, he says.

Regional differences
Unlike California, late planting in other parts of the country can have significant impacts on diseases and other pests, which should be managed accordingly if you go beyond targeted planting dates.

In Louisiana, yields of all varieties start to fall off significantly after May 1 in the south part of the state and four weeks later in the northeastern portion, says John Saichuk, Extension rice specialist at Louisiana State University’s AgCenter in Crowley.

Yield potential continues to drop proportionately the longer the delay. In Louisiana, he says, many growers make a decision to plant late based largely on market conditions for rice and crawfish, which are often raised prior to rice on flooded fields.

“At some point, growers have to decide if they are going to stop catching crawfish and start planting rice,” he says. “It’s simply a business decision.”

Expect more disease pressures
If you choose to plant late, you should expect to make at least one fungicide application, Saichuk says. That’s because late planting leaves young plants more susceptible to diseases as higher spore populations move into the field.

You should scout early and often for signs of disease, particularly if the field has a history of sheath blight or blast, and consider timely fungicide applications.

False smut can also be more prevalent in late-planted rice, so consider a fungicide that contains propicanazole if you have a history of smut in your fields.

“If you plant late, you can guarantee having a blast or sheath blight problem in south Louisiana or a sheath blight problem in north Louisiana,” he says. “There are significant differences in return based on applications of fungicides, and you can assume the damage you would sustain will be even greater when you plant late. As a result, a fungicide application may be even more beneficial.”

Late plants are also more vulnerable to insects, including rice water weevil and stink bug later in the season, and you should plan on scouting early for insects and staying on top of them immediately after flooding.

In Louisiana, fertility and water management will be similar under various planting dates, unless you are basing nitrogen applications on yield potential. In that case, keep in mind that yields will be reduced and rates should be adjusted accordingly.

Variety selection
Chuck Wilson, University of Arkansas Extension rice agronomist in Stuttgart, receives calls every year from growers who are planting late and want to know what variety to select. The optimum cut-off date for planting rice in Arkansas is May 20, and growers who go beyond June 10 can expect significant declines in yield of up to 40 percent compared to an early April planting.

As a result, if you’re forced to delay or replant fields beyond May, consider the loss in yield potential when making decisions about variety and inputs. Variety selection should be based on your willingness to absorb extra input costs as well as its maturity and susceptibility to increased disease pressures.

Fields where growers have clay soil, good water availability and the ability to hold the flood can withstand late plantings and yield relatively well under high-performing varieties, such as Wells and Francis.

Under less-optimal conditions, Wilson says, you may want to consider older varieties that will yield less but require fewer inputs.

“Relatively speaking, you know you’re going to have a low yield, so you may want a decent yielding variety with as little input as possible,” Wilson says. “Drew and Kaybonnet have relatively low fertilizer and fungicide requirements, so you can grow them cheaper than a high-input/high-return variety. You know you’re not getting the yield, so you may not want to pick a variety where you will have to spend $60 an acre on fungicide costs.”

The same is true for nitrogen inputs. While newer varieties may require up to 150 units of nitrogen per acre, Kaybonnet and Drew require as little as 35 units per acre.

Increased insect pressures also should be expected in Arkansas, and you should expect to scout early and make additional insecticide applications under late-planted rice. You should expect more stink bug pressures as populations build up throughout the state later in the season.

Experts in all regions agree that while there are steps you can take to mitigate late planting impacts on yield, decisions must be made on a field-by-field basis, based on your economic situation, field history, yield potential and risk tolerance.

“You have to look at the individual situation, Wilson says.