Soil survey maps have been available  for  many  decades. The  first  Texas  survey  was published in 1902 in a U.S. Department of Agriculture report. It consisted of 12 pages of text and five mapping units within an area of 137,000 acres.

In  earlier  times,  the  maps were  printed  on  large  sheets about  the  size  of  a  card  table top. The Temple Public Library has several published over the past century. Those early maps are gold mines of historical information about long-dissolved communities, rural cemeteries and  land  features  now  disguised by urbanization.

However,  information gleaned from them was cursory because  early  20th-century knowledge  and   survey  tools were primitive. “A lot of those early surveys were done on the ground  with  guys  setting  up plane  tables  in  a  pasture,” Williamson added.

Early soil scientists measured the ground with a horse-drawn buggy. They would  tie  something to the spoke of the wheel and  count  the  revolutions  to obtain  an  accurate  measurement. First automobiles, introduced  into  the  field  work  in 1919,  lacked  odometers.  So, the  soil  scientists  would  pull the buggy behind the automobile to measure the land. Then, they tried mounting the buggy wheel onto the side of the auto. This was fairly successful unless the automobile made sharp turns and skidded. Finally, the scientists added newly developed odometers to the autos.

The  survey  continued  over the next century, in stops and starts as funding was available and technology improved.

In recent decades, the soil scientists’ work was enhanced by a  host  of  technological  wizardry – high-resolution aerial photography,  global positioning satellites, interactive software  and  computer-assisted drawing.

Survey  crews  in  the  beginning  targeted  the more populated counties or regions with strong agricultural economies. Bell and surrounding counties were among the earliest studied. The least populated counties, such as sparsely populated areas in West Texas, were the last to be surveyed. The actual “last  acre”  is  on  private  land between  Van  Horn  and  Dell City in Hudspeth County, population 3,115 and located immediately east of El Paso.

“It’s  not  that  those  counties weren’t  important,” Williamson said. “It’s just that, at  the  time,  the primary  land use  was  not  as  intensive  and the counties were sparsely populated.”

In  all  cases,  soil  scientists take  general  inventories  of each county. They contact the landowner  for  permission  to dig samples and map the soil. The  scientists  take  numerous samples  because  not  all  soils are alike; one pasture can contain several different soil types.

“Normally you’ll  find 40 to 50 different soil types in every county,”  Williamson  said. “Using aerial photography, we record where the different soils occur  on  the  land.  Then  we take all  the  information, send samples  to  the  laboratory  or test it locally. We analyze how much sand or clay is in the soil, also the amount of lime and the pH, or acidity, of the soil,” he added.

As they walked or drove vast expanses of the state, soil scientists described and sampled soils,  then  sent  them  to  the Texas  A&M  University  and Texas  Tech  University  Soil Laboratories  as  well  as  the NRCS  National  Soil  Survey Laboratory  for  further  analysis.

Once those analyses are finished, soil scientists draw conclusions from the results found in the test site, creating a crazy quilt of polygons and swirling shapes  across  the  map’s  terrain. This  aggregate  yields  a mother lode of information.

“We can determine soil capability for septic  tank systems or building homes. These maps are  helpful  to  determine  the best  location  for  roads  or buildings, planting gardens or deciding what type of crops to plant and how productive the land will be. Ranchers use the maps  to  decide  how  many head of cattle they can run on their acreage, depending on the soils productivity,” Williamson said.

“The  soil  resource  is worth billions and billions of dollars. In  recent  years,  maps  have been digitized and put on the web where everyone has free access. Think how  important soil  resources  are! This  year alone, Texas soil produced $25 billion  in  agricultural  products,” Williamson said.