June 28, 2001

Dryness Negatively Impacts Tamaulipas Sorghum

Summary

When Tropical Storm Allison exited the Texas/Mexico region of the Gulf coast, with her went the last chance for the rain-fed fields of north Tamaulipas state to render a normal-to-above-normal level of sorghum production in the June/August 2001 harvest.  Tropical Storm Allison delivered over three feet of rain to the Gulf coast of the United States in early June, but northeast coastal Mexico saw little more than brief showers during that period. Producers frequently turn to sorghum when moisture is at a premium, however the continuing absence of appreciable precipitation has combined with temperatures 1-4 degrees above normal to deliver a shock to the sorghum fields of northeast Mexico, from which they are unlikely to completely recover.

Sorghum Is Adaptable - To a Point

The spring/summer season provides the main Mexico sorghum crop, however the fall/winter crop advanced to between 30-42 percent of the annual total during the 1990s because nationwide dryness led to increased fall/winter area planted to sorghum. Tamaulipas regularly provides 75 percent or more of the Mexican fall/winter sorghum crop. Producers have seen the annual monsoon arriving late to Tamaulipas state frequently in recent years, and the extended drought across north Mexico persuaded some producers to delay planting until late March and even April. A sorghum plant limited in size by poor environmental conditions during the vegetative stages can partially overcome that limiting factor if good conditions exist during the grain head filling stage. Indications are that early-maturing sorghum yields are not as high-yielding as the late-maturing sorghum. Sorghum normally can tolerate extended exposure to high temperatures approaching 38 degrees Celsius, however high temperatures plus moisture stress during blooming will negatively impact yield.  The following maps illustrate the level of dryness in Tamaulipas for Spring 2001.

Soil Moisture Maps based on WMO Station Meteorological Reports

North Tamaulipas fields seeded prior to March 1, 2001 had the benefit of scattered showers during late- April, early-May, and late-May, a circumstance of critical important because crop roots found little subsurface moisture to draw upon. Those pre-March fields may have reached the dry down stage June, and perhaps profited from the heat, but yield will not be high. Fields seeded after March 15, 2001 were in the blooming and grain-filling stages when June arrived with plus-35 degree temperatures, and reduced yields will result from that coincidence.  The following graphs illustrate the level of heat and the sparse precipitation in Tamaulipas for Spring 2001.

Temperature Graphs (Celsius) for selected stations in north Tamaulipas

Precipitation Graphs (Millimeters) for selected stations in north Tamaulipas

With little water available, the sorghum plants slowed their head-filling activity to withstand the weather conditions, and likely will not recover from consecutive weeks of insufficient moisture. Any sorghum fields seeded after April 1, 2001 will need an improved precipitation scenario to survive. If they survive, those late-planted fields will ultimately yield the best weight.  Tamaulipas sorghum traditionally is trucked to poultry and livestock operations around Monterrey (state of Nuevo Leon) and the Central Plains.

In the two AVHRR scenes below, the shades of red indicate vegetation in varying stages of growth.  The pale pink fields to the right of the white crosshair in April 2001 scene represent sorghum plants recently emerged, while the pale red areas were sorghum plants further along in development.  In the May 2001 scene, some of the sorghum fields had matured, but many were less vibrant than a month earlier due to environmental stresses. 

Mexico Sorghum Production Since 1995

For more information, contact Ron White with the Production Estimates and Crop Assessment Division on (202) 690-0137.