Commodities: Fieldcrops: Peanuts: 2008 Peanut Update

2008 Peanut Update

Using Climate and Weather Information for Management of Peanut

Joel O. Paz and Gerrit Hoogenboom

The drought that started in 2006 extended into the 2007 growing season. Extremely dry conditions in the spring resulted in delayed planting. Extended periods of no rain resulted in a highly stressed peanut crop in several counties in Southwest Georgia. A heat wave struck Georgia in August when temperatures reached over 100 oF in several areas (Figure 1). 
Figure 1.  Daily maximum temperature of over 90 oF recorded by several AEMN stations from August 5 to August 19, 2007 (Source: www.georgiaweather.net).

Weather records show that the state has experienced long periods of high daytime temperatures in the past (Table 1).  For example in Bainbridge, maximum temperatures of more than 90 oF were recorded for the entire month of August.  These events happened twice – in 1954 and 1990.  The drought in 2007 certainly evoked memories of the drought that the state experienced back in 1954, 1986, and 1990.   

Table 1.  Number of days with temperatures greater than 90 degrees Fahrenheit in Georgia  

Source: National Climatic Data Center

Low rainfall amounts and high evapotranspiration rates contributed to a high water deficit in several peanut growing areas, especially in the Southwest corner of the state. A summary of the water balance for the 2007 season is shown in Table 2.

The weather conditions and events that occurred last year do not necessarily indicate that we will experience similar conditions in 2008.  We have to consider the regional climate conditions and projections and look at historical weather data to see how the 2008 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.

AgClimate (www.agclimate.org) is an interactive web site developed by the Southeast Climate Consortium (SECC) to assess different management options with respect to their probable outcomes under forecasted climate conditions.  Seasonal climate forecasts are developed by climatologists.  These forecasts give the growers an idea what to expect for the next three months in terms of climate conditions in Georgia.  The forecast for the winter of 2008 in South Georgia calls for warmer temperatures and drier conditions.  This assessment was based on a La Niña, which increased its strength and extent in Fall 2007 and can now be considered a moderate to strong event.  The possibility of warmer-than-normal temperatures and dry condition extending into early spring 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.agclimate.org for updates on short and long-term climate outlooks.

One of the web-based applications or tools on the AgClimate website allows a user to evaluate the climate forecast based on the ENSO phase, and to examine average and deviation from normal. The web site also provides 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 for Mitchell county, Georgia.  To access this web-based tool, use your computer browser and go to www.agclimate.org. On the left navigation bar, click on ‘Agclimate 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 Mitchell county, Georgia. 

The Crop Yield Risk Forecast tool is another web-based application on AgClimate that incorporates climate information.  This tool helps users analyze yield potential based on climate forecast, planting date, soil type, and management scenario including irrigation.  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 AgClimate website, click on ‘Agclimate Tools’ >> under the Crop Yield section, click ‘Yield Risk Forecast’.  You can pick an ENSO phase, choose an irrigated or rain fed scenario, and select different planting dates to examine the probability distributions of peanut yields (Figure 3). 

Figure 3.  Yield distribution of irrigated peanuts for two planting dates under La Niña condition in Mitchell 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 Georgia Automated Environmental Monitoring Network (AEMN) provides a valuable resource for growers looking for reliable and up-to-date weather information in their area. The network which added three weather stations (Ossabaw, Danielsville, and Baxley) last year now has a total of 74 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 http://www.georgiaweather.net. Current weather data and weather-based tools are available for each location (Figure 4).

Figure 4. The web page showing available data and simple calculators for each location in the network.

Table 2.  Water balance from May 1-October 31, 2007 compared to normal values (1971-2000) for several AEMN weather stations located in peanut-producing areas.

Click here for larger image!

*Rainfall values were rounded off to 0.1 of an inch.  ET is evapotranspiration

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