Weather patterns point to early planting advantages

Weather patterns point to early planting advantages

• Given typical La Niña weather patterns, crop simulation models show a very high probability of high yields with an earlier planting date.

While nothing is certain about the weather, forecasters’ best bet for this spring is that farmers in the lower Southeast could benefit from earlier planting dates.

“Given typical La Niña weather patterns, these crop simulation models show a very high probability of high yields with an earlier planting date,” says David Zeirden, Florida’s state climatologist.

With crop simulation models, forecasters can vary factors like planting dates, soil types and irrigated or non-irrigated cropland. “If you plant at about the middle of April, it shows a very good probability of high yields and a low probability of low or medium yields. If we go to a later planting date, with the same weather inputs, the probability of high yields goes down while the probability of medium to low yields goes up,” said Zeirden, speaking at this year’s Wiregrass Cotton Expo held in Dothan, Ala.

The recommendation, he repeats, would be to plant as early as you can. “The reason behind that is that while we’ve had rainfall — though it has been a La Niña — if you plant early and take advantage of that soil moisture, get the crop established, and make it through the spring dry season, then hopefully you can take advantage of that summer rainfall at a critical time when the plants need it the most,” he says.

A disclaimer, just when you think you have the weather figured out, Mother Nature shows you who’s the boss. This winter hasn’t been a typical La Niña winter, being much colder than anticipated and not as dry as we thought it’d be.

It has been an extremely frustrating past two years, for farmers, says Zeirden. In 2009, the problem was rainfall. “I won’t go so far as to say it was too much rainfall, it just occurred at the wrong time and created so many problems getting the crop out of the field. In 2010, the problem was a lack of rainfall, and the lack of rainfall occurred at the critically wrong time, when crops were reproducing and flowering,” he says.

Looking at historic yields over the past 40 or so years in the Wiregrass region for peanuts, yields are fairly consistent, but with a number of catastrophic or down years, he says. These years were 1980, 1990 and then again in 2000.

“We looked into this 10-year cycle last year, and we couldn’t find any climate conditions in common with these other years. The El Niño or La Niña phases didn’t match up in these years. We thought it was maybe an artifact of the data and didn’t think it would happen again in 2010, but lo and behold, it did.”

Cotton sensitive to changing weather

Turning to cotton data from the Wiregrass region and Coffee County in particular, cotton seems to be much more volatile from year to year, being more sensitive to changing weather conditions, says Zeirden.

“We saw down years in 1980, 1990 and again in 2000, and 2010 was another very bad year.

“We’ve plotted summer rainfall — May through August. In 1970, the rainfall wasn’t that bad, so it tells us that rainfall wasn’t the whole story, or maybe the timing of the rainfall was more critical. There is a correspondence between rainfall and yields, but timing is almost more important than the amount of rainfall. This doesn’t take into account fall and winter rainfall, and the conditions you plant into in terms of soil moisture.”

Last year, during the winter and spring, we were in a moderate to strong El Niño, which is warm water in the tropical Pacific Ocean, says Zeirden. El Niño usually brings winter and spring weather that includes frequent rainfall, winter storminess, cooler temperatures, but abundant or above-normal rainfall.

“For the most part, we saw that in the Southeast last year, and that was good news going into planting season,” he says. “When we got into the month of May, when the influence of El Niño is not as strong, we still had good news with ample rainfall amounts. So we had plenty of winter moisture and rainfall in May. But in June and July, the faucet was turned off. We had 25 percent of normal rainfall for the month of July in southeast Alabama.

“This pattern wasn’t totally unexpected because we’ve seen many times before in the summer, as we come out of an El Niño winter, that June and July can turn drier than normal in the Southeast. We had a couple of tropical systems in the Gulf last year, but all of the rainfall fell on the south side of the storm, which is unusual.”

Rainfall wasn’t the only player last year, says Zeirden. In addition to the lack of rainfall, it was one of the top three hottest summers in the past 100 years in Florida, Alabama and Georgia. This caused high evapotranspiration rates, sucking the moisture from the soil.

Returns every two to seven years

El Niño returns every two to seven years, he says. The opposite phase is La Niña, where a similar area of the Pacific Ocean turns several degrees colder than normal. The transfer of heat and humidity in the upper atmosphere can affect the circulation patterns of the Northern Hemisphere and across North America.

La Niña usually brings warmer winters, drier winters, more sunshine and less storminess to the Southeast. “We have a very strong La Niña this year, and warm air is pushed farther west than usual. Australia is feeling its impact, with torrential rainfall and a category 5 tropical system.

We really didn’t see a warm and dry winter this year, but other parts of the world have.”

El Niño’s are most commonly one-year events while La Niña’s can last three or four years in a row, more recently in 1999 through 2001. This can set up a multi-year drought situation when you’re farming in the Southeast, says Zeirden.

“This appears to be one of the strongest La Niña’s ever. Because of the strength of it, there’s probably a better chance than usual of it lasting multiple years. Chances are we’ll have to deal with it not only this growing season, but into harvest season and into next year.”

To determine how a La Niña affects precipitation patterns over the Southeast, forecasters take weather observations from 60 years of the weather events — about 13 episodes — average them altogether, and compare them to the long-term average, says Zeirden.

“The good news is that the influence of these weather patterns tends to go away in the springtime, in April. When we have a La Niña, when we get into May or June, it kind of reverses itself. So over the Florida Panhandle and southeast Alabama, we can expect more rainfall than normal with this weather event. So this is a bit of good news and some hope for the coming year.”

But the wintertime patterns are much more consistent with the events and much stronger, he adds. “Looking at summertime patterns over the Pacific Ocean, we don’t have as much confidence that they’ll return every time.”

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