April 5, 2002

Oklahoma Crop Condition Update - April 2002

Special Report: Oklahoma Winter Wheat Condition

Summary

Rainfall during September-October 2001 favored planting, emergence, and establishment of the 2002 Oklahoma winter wheat crop.  Soil moisture levels in fall 2001 were much better for wheat planting and growth than those experienced a year ago for the 2001 (fall 2000) wheat crop.  Precipitation during winter-early spring 2001/2002 was much below normal, as well as below that registered over the past few years.  Low soil moisture levels during Spring 2002 have resulted in poorer winter wheat conditions in Oklahoma as of April 1, 2002, compared to recent years.

Crop Conditions 

According the USDA's National Agricultural Statistics Service (NASS), Oklahoma farmers planted 5.8 million acres of wheat in fall 2001, up four percent from the previous year.  On April 1, 2002, NASS reported that 55 percent of the Oklahoma's wheat crop was in poor to very poor condition.  In early April 2001, 26 percent of the Oklahoma crop was rated as poor to very poor, compared to only 4 percent in April 2000.  Satellite images from March 2002 indicate that crop conditions are currently greener than those seen in March 2001; however, more of the planted area last year  was still dormant or low in growth due to cold spring 2001 weather.  PECAD's soil moisture model supports that crop conditions are much worse this year in late March, compared to 2001 and 2000.

Click on any of the soil moisture maps to see a larger map

Soil Moisture 

As can be seen in the soil moisture maps (above), soil moisture as of March 25, 2002, is much lower than in March 2001 or 2000.  On March 25, in 2000 and 2001, soil moisture was adequate to surplus, as shown by the dark green across North Central Oklahoma, a major rain-fed wheat growing area.  PECAD's soil moisture model indicates that this year North Central Oklahoma and much of the western half of the state are undergoing a drought, shown in red.

Rainfall  Graph

Precipitation data provided by the U.S. Air Force AGRMET Program, was monitored and graphs are provided for each of Oklahoma's significant four wheat growing crop districts.  In most districts, rainfall for the 2002 crop started much earlier (September and October 2001, show in red, than the previous year (shown in yellow).  However, by November 2001, it was evident that precipitation for this year's wheat crop was trending much below recent years.  This growing season's rainfall (in red) is only better than previous years in the eastern Oklahoma crop districts, which are not significant wheat producers.  Light precipitation (some in the form of snow), during late February and March maintained crop conditions at their current levels.  Without additional moisture, the crop will deteriorate further as temperatures become more seasonally warm and growth activity resumes.  Last year, timely rainfall and favorable temperatures during April and May greatly improved wheat crop conditions from levels observed during March. 

Precipitation Graphs by Districts

• North Central Crop District
   

• Central Crop District
   

• West Central Crop District
   

• Southwest Crop District
   

Temperatures

Temperatures during spring 2002 have been below normal, and below spring 2000 and 1999 levels.  However, this year, especially winter, has been warmer than last, which was much colder than normal.  Also, cold spring temperatures last year slowed growth and development. 

Temperature Graphs

• Ponca City, Oklahoma
   

• Enid, Oklahoma
   

• Oklahoma City, Oklahoma

Imagery

Above is a NOAA 16 satellite image of Oklahoma, as seen on April 1, 2002.  The "brighter red" area running from the north central border with Kansas to the southwestern border with Texas contains the major winter wheat producing counties.  The red is primarily winter wheat.  Slide 1 compares satellite images from April 2000 with this scene from April 1, 2002.  It is evident from slide 1 that as of early April, winter wheat conditions were much better in 2000 than they are currently.  Slide 2 includes Vegetation Index Maps from the last half of March, comparing March 2000 with March 2002.  Due to problems with satellite data, no image for the last half of March 2001 is available.  This map clearly shows how much less vigorous vegetation is this year across Kansas, Oklahoma, and Texas, compared to a year ago.  Both temperatures and moisture levels account for this year's lack of greenness.  A Southern Plains Wheat Production map (five-year average), shows the typical wheat production distribution across the Southern Plains. 

Slide 3 is a comparison of two Landsat TM images from an area around Enid, Oklahoma.  In March 2000 crop conditions were very good.   The "red" is very good, growing winter wheat.  The purple is ice remaining from a spring snow storm.  The 2002 crops are uneven in development and not as vigorously growing. 

Slide 4 and Slide 5 are Landsat TM images from Alfalfa County, at Cherokee, Oklahoma, comparing March 2000, and March 2001 images with a March 9 scene from 2002.  Again the 2000 crop looks uniform and in very good condition.  The 2001 and 2002 crops are winter stressed and drought stressed and in general uneven in development and condition. 

Conclusions

While it is too early to determine the final outcome of the 2002 Oklahoma wheat crop, it is evident that the crop would benefit greatly from frequent and timely rainfall.  If moisture does not come soon, statewide wheat conditions could soon deteriorate to levels not seen since 1989.

For more information, contact Carl Gernazio of the Production Estimates and Crop Assessment Division at 202-690-0136.