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March 15, 2007

Cotton pickin’ accurate forecasting tool for growers

With unpredictable weather nationwide, it is especially important to know when to plant crops to produce the highest yield.

   Fruiting branch with open flower and squares.

Fruiting branch with open flower and squares.
Photo by Jack Kelly Clark

Before the advent of a weather forecasting tool, cotton growers could only plant their crops based on soil moisture and soil temperatures that they saw in their fields. If farmers delayed planting, hoping for better weather, they risked losing time to produce a good crop. If they planted too early, they might get higher yields, but they increased the risk of cold weather damage and the threat of replanting.

Fresno Farm Advisor Daniel Munk cautions cotton growers not to plant seeds too early this year because they are especially vulnerable to chilling injury that can impact early growth and yields.

Munk recommends using the 5-degree day weather forecasting tool found on the UC Statewide Integrated Pest Management Program Web site at www.ipm.ucdavis.edu to determine a field planting date. “The 5-day heat unit forecast gives excellent guidance when it’s used in combination with grower soil temperature data.

“Timely cotton planting is especially important this year because growers will likely plant more Pima cotton, an extra-long staple cotton that needs an extra one to two weeks to mature compared to the traditional Acala cotton,” says Munk. “Early planting followed by good early season management and strong early fruit retention can translate into higher yields produced in a shorter period of time. Shortening the cotton growing season through early planting can also reduce costs by decreasing crop exposure to late season pests and the need for late insecticide and defoliant applications.”

In 1997, the UC IPM information systems group began posting the weather forecasts on their Web site each day during cotton-planting season. The observed lows for the morning (as reported for Fresno, Bakersfield and Chico) are used as the minimum temperatures for the first day of the period. The page is updated each day from about March 10 through April 30 every year.

The planting forecast categorizes the predicted heat units, which are units that combine temperature and time used to monitor growth and development of organisms, into degree-day groups of ideal, adequate, marginal, and unfavorable.

More information about this beneficial tool can be found on the UC IPM Web site, or by contacting your local farm advisor.


High-resolution image (348KB) "Fruiting branch with open flower and squares." Photo credit: Courtesy of UC Statewide IPM Program, by Jack Kelly Clark. Photos are for use with this release only. All other uses see Legal Notices.


Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

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