The official description of the Port series can be seen at the following web sites:
http://www.statlab.iastate.edu/cgi-bin/osd/osdname.cgi?-P
http://www.statlab.iastate.edu/soils/osd/
The Port series consist of very deep, well-drained, moderately permeable flood plain soils that formed in calcareous loamy alluvium of Recent age. These nearly level to very gently sloping soils are on narrow flood plains in the Central Rolling Red Prairies
(MLRA-80A) and the Central Rolling Red Prairies (MLRA 78C). Slopes range from 0 to 3 percent. Mean annual precipitation is 32 inches. Mean annual temperature is 63 degrees F.
(US) SOIL TAXONOMY: Fine-silty, mixed, superactive, thermic Cumulic Haplustolls
Order - Mollisols - Dark colored, base rich, mineral soils, many developed under grass.
Suborder Ustolls - Freely drained Mollisols of subhumid to semiarid climates.
Great group - Haplustolls - Ustolls with weakly developed subsoils.
Subgroup - Cumulic Haplustolls - Haplustolls with organic carbon that decreases irregularly with depth or remains at high levels to 125 cm or more.
Family Criteria:
Fine-silty - 18 to 34% clay and <15% between 0.1 and 74 mm.
Mixed - Not dominated by any one mineral and < 90% quartz and other resistant minerals in the sand fraction.
Superactive - Cation exchange of 60 cmol(+)/kg clay or more
Thermic - Mean annual soil temperature of 15 to 22 degrees C and > 6 degrees difference between mean summer and winter temperature.
FAO Classification: Mollic- Eutric Fluvisols
I am not familiar with the Dutch system of classification.
