Commodities: Fieldcrops: Peanuts
2009 Peanut Update
USING CLIMATE AND WEATHER INFORMATION FOR MANAGEMENT OF PEANUT
Joel O. Paz and Gerrit Hoogenboom
Although we had a few dry spells last year, especially during the month of May and from August 26-Sept 30, timely rains contributed to an overall good peanut growing season. A summary of the water balance for the 2008 growing season is shown in Table 1. The water balance provides a quick look at the amount of water that is in surplus or in deficit calculated based on the incoming water (rainfall) minus the demand for water in the form of evapotranspiration (ET). A negative value means ET is higher than rainfall for a particular period. Based on the normal values (1971-2000), weather stations in peanut growing areas recorded deficits of roughly 6 to 10 inches during the growing season. In 2008, several stations had water balance deficits, and a few stations, notably, Cordele, Midville, Statesboro, Jeffersonville and Tennille had significant water balance deficits (> 13 inches). Only a few stations recorded surplus water balance, namely, Attapulgus, Camilla, Cairo, Dawson, Dawson-HHERC, and Sasser.
Heavy rains from tropical storm Fay in August brought much needed moisture in Georgia. Several weather stations of the Georgia Automated Environmental Monitoring Network (www.georgiaweather.net) recorded over 10 inches of rainfall during Fay’s slow track across the region. The station in Cairo recorded the highest amount of precipitation (16.7) from August 22-26. Attapulgus had 16.3 inches; Newton (13.0 inches), Camilla (10.8 inches), and Dixie (10.8 inches) also received significant amounts of rain (Figure 1). The amounts are staggering especially if we compare these values to the total rainfall that had been received prior to the storm.
Table 1. Water balance from May 1-October 31, 2008 compared to normal values (1971-2000) for several AEMN weather stations located in peanut-producing areas.
*Rainfall values were rounded off to 0.1 of an inch. ET is evapotranspiration
Figure 1. Rainfall amounts recorded at several AEMN stations before and during tropical storm Fay.
The weather conditions and events that occurred last year do not necessarily indicate that we will experience similar conditions in 2009. We have to consider the regional climate conditions and projections and look at historical weather data to see how the peanut 2009 growing season will shape up. The climate in Georgia is strongly affected by a phenomenon called El Niño-Southern Oscillation (ENSO). When the sea surface temperature in the eastern equatorial Pacific Ocean is higher than normal, the phenomenon is referred to as El Niño. When the temperature is lower than normal, the climatic event is referred to as La Niña. When the temperature is normal, the event is referred to as Neutral. El Niño years tend to be cool and La Niña years tend to be warm between October and April. In terms of rainfall amounts, El Niño years tend to be wet and La Niña years tend to be dry during these months. The ENSO signal in the region is strongest in the fall and winter months and some evidence exists that La Niña summers tend to be slightly wetter than normal.
AgroClimate (www.agroclimate.org) provides seasonal climate forecasts developed by climatologists working with the Southeast Climate Consortium (SECC). These forecasts give the growers an idea what to expect for the next three months in terms of climate conditions in Georgia. As a reference, the SECC predicted a dry and warm winter and early spring 2008 due to a La Niña. La Niña then slowly changed to neutral conditions in the summer. Neutral conditions are expected to continue through the winter of 2009 and possibly longer. However, the atmosphere over the Pacific is giving mixed signals. The Southern Oscillation Index, which is a difference in surface barometric pressure between the central and western Pacific, is strongly positive at this time and more consistent with La Niña. In addition, the easterly trade winds over the central Pacific have been consistently stronger than normal which could lead to a cooling of Ocean temperatures. On the other hand, weather patterns over the Southeast U.S. have been colder than normal with frequent cold front passage which is very uncharacteristic of La Niña conditions. This all means there may be a chance that La Niña conditions might return sometime this winter or early spring.
Without a well-defined El Niño or La Niña in the Pacific, there is no indication that temperatures or rainfall will be either above normal or below normal. More variable weather is common in neutral winters, with periods of very cold weather mixed in with warm spells. Near-normal rainfall is the best forecast, as there is no El Niño or La Niña to tip the balance towards wetter or drier.
What if La Niña returns in early spring and what are the possible impacts on local conditions? In a La Niña, there is a higher likelihood of warmer temperatures and lower-than-normal rainfall -- conditions which may affect planting date decisions. Although conditions may vary during the growing season, we will continue to provide current climate-based information to help growers manage their peanut farm operations. Check www.agroclimate.org for updates on short and long-term climate outlooks.
Climate-based tools developed by the SECC allow users to assess management options with respect to their probable outcomes under forecasted climate conditions. One of the web-based applications or tools on the AgroClimate website allows a user to evaluate the climate forecast based on the ENSO phase, and to examine average and deviation from normal, and detailed rainfall and temperature predictions for all counties in Georgia. As an example, Figure 2 shows the deviation from average rainfall for each month under La Niña in Seminole county, Georgia. To use this web-based tool, use your computer browser and go to www.agroclimate.org. On the left navigation bar, click on ‘AgroClimate Tools’ >> under the Climate section, click ‘Climate Risk’. You can select an ENSO phase (El Niño, La Niña, and Neutral), and examine how the different climate variables (rainfall, temperature) are affected by ENSO.
Figure 2. The climate risk tool showing the deviation from average monthly rainfall for La Niña years in Seminole county, Georgia.
The Crop Yield Risk Forecast tool is another web-based application on AgroClimate that incorporates climate information. This tool helps users analyze yield potential based on climate forecast, planting date, soil type, and management scenario including irrigation (Figure 3). A crop model simulates growth and development of a particular crop (for example, peanut), and how it responds to different environmental conditions. To use this tool on the AgroClimate website, click on ‘Agroclimate Tools’ >> under the Crop Yield section, click ‘Yield Risk Forecast’. You can pick an ENSO phase, choose irrigated or rainfed scenario and select different planting dates to examine probability distributions of peanut yields.
Figure 3. Yield distribution of irrigated peanuts for two planting dates under La Niña condition in Colquitt County, Georgia.
Growers can use current weather information to decide on what to do in terms of farm management operations including planting, pesticide application, irrigation, and harvesting. The AEMN web site (www.georgiaweather.net) provides a valuable resource for peanut growers looking for reliable and up-to-date weather information in their area. The network which added three weather stations (Sparta, Odum, and Howard) in 2008 now has a total of 77 stations across the state. Each station monitors air temperature, relative humidity, rainfall, solar radiation, wind speed, wind direction, soil temperature at 2, 4, and 8 inch depths, atmospheric pressure, and soil moisture every 1 second. Data are summarized at 15 minute intervals and disseminated through its web site at www.georgiaweather.net. Current weather data and weather-based tools are available for each location (Figure 4).
Figure 4. A web page showing available data and simple calculators for each location in the network.
Here is a sample web page that shows the 31-day summary of weather variables including rainfall and evapo-transpiration (ET). |
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Attapulgus Weather Station