The soil survey covered an area in west-central Puerto Rico composed of two 8 km- (5 miles-) wide strips on each side of the military road (now highway PR 10) from Arecibo on the north coast to Ponce on the south coast. The survey area was approximately 885 km2 (330 square miles; 85,500 ha, 211,200 acres), which is about ten percent of Puerto Rico's land area. The location of the transect was an excellent choice. It represented most of the island's diverse physiographic regions and agroecological zones: Holocene and Quaternary swamps and alluvial deposits along the north coast; a karst region developed in Tertiary limestone; the dissected humid uplands of the Cordillera Central composed of Cretaceous volcanic and plutonic rocks; the southern subhumid limestone belt; and the floodplains and lagoons on the semiarid south coast.
Dorsey and his colleagues differentiated 16 “soil types” such as Arecibo sand and Ponce loam, and two land units (coral sand, riverwash). Organic matter and particle size distribution were determined for one or more pedons of each of the 16 soil types. No profile descriptions were provided, but the salient morphological features were mentioned. Reflecting the partial sponsorship of the survey, a comparatively large section of the narrative for each soil type was focused on agricultural considerations. The authors noted a pattern they had observed in the United States, namely, that the farmers, through empirical observations, had discovered the soils best suited to their crops. The authors also expressed some humility in admitting that understanding soil-plant relationship was not yet sophisticated enough to utilize soil surveys to predict the value of new agricultural enterprises. But they urged the experiment station and Bureau of Soils to collaborate further.
In 1928, the Division of Soil Survey (USDA) and the University of Puerto Rico Agricultural Experiment Station initiated a detailed and comprehensive survey of the soils of Puerto Rico. Ray C. Roberts was in charge of the survey party, which over the duration of the fieldwork consisted of 25 soil scientists, prominently including James Thorp. This survey, published in 1942, benefited from developments and refinements in soil science and soil surveying. It especially benefited from work in other tropical countries and territories, including Hugh H. Bennett's and R. V. Allison's work in Cuba.
During 1965-2003, Standard Order 2 soil surveys at a scale of 1:20,000 for all of Puerto Rico were published in the following area reports: Lajas Valley Area, Mayaguez, Humacao, San Juan, Ponce, Arecibo, and the Caribbean National Forest. The first two of these reports, Lajas and Mayaguez, were unique in being published in both English and Spanish text. All of the surveys except the Lajas Valley Area, first published in 1965, used Soil Taxonomy. That survey is now being updated. Further updates are planned for the rest of the Island. In a departure from recent practice, the new updates will be based on Major Land Resource Areas rather than the political boundaries.
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