General view of an unidentified apparatus at a U.S. Department of Agriculture facility. A radioactive materials sign and protective glass panel are visible to the right of the apparatus. The U.S.D.A. commonly used…

General view of an unidentified apparatus at an unidentified U.S. Department of Agriculture facility.

General view of an unidentified chemist handling radioactive material at an unidentified U.S. Department of Agriculture facility. The U.S.D.A. commonly used radioactive material for a variety of research and testing,…

General view of assorted equipment and apparatus in the Constant Humidity Room at the the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn…

General view of assorted equipment and apparatus in the Constant Humidity Room at the the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn…

General view of an unidentified room at the U.S. Department of Agriculture's Agricultural Engineering Laboratory showing a drillability apparatus with fertilizer hoppers, a starwheel, and rotating plate mechanism.

Component parts, likely of a drillability apparatus, used at an unidentified U.S. Department of Agriculture facility.

General view of the drillability machine at the U.S. Department of Agriculture's Agricultural Engineering Laboratory showing the distribution of wet granular fertilizer as deposited by the Grether hopper.

General view of an unidentified worker sorting raw material, possibly ore or phosphate, at a Fixed Nitrogen Research Laboratory plant. The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American…

Exterior view of the Fertilizer Machinery Laboratory at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. Established by an act of Congress in April 1900, Arlington Farm served as the main field…

General view of the Air Control Room at the U.S. Department of Agriculture's Agricultural Engineering Laboratory showing three bags of fertilizer in storage under three bags of sand.

General view of the fertilizer distribution testing apparatus used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. The…

General view of fertilizer storage piles supported between uprights at the U.S. Department of Agriculture's Agricultural Engineering Laboratory. Text accompanying the photograph notes that each row contained a full set…

Close-up view of the mounting frame and driving mechanisms of the fertilizer distribution testing apparatus used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington…

General view of fertilizer trays on a suspension apparatus at an unidentified U.S. Department of Agriculture facility.

General view of the trays used to expose fertilizer to humidity in the Air Control Room at the U.S. Department of Agriculture's Agricultural Engineering Laboratory.

View of chemist George Wieczorek (right) using a Geiger counter to measure ionizing radiation in an unknown substance, likely soil or fertilizer, at an unidentified U.S. Department of Agriculture facility.

View of chemist William A. Jackson using a Gieger counter to examine a package at an unidentified U.S. Department of Agriculture facility. The U.S.D.A. commonly used radioactive material for a variety of research and…

View of chemist George Wieczorek (right) and an unidentified chemist using a Geiger counter to measure ionizing radiation in an unknown substance at a U.S. Department of Agriculture facility. The U.S.D.A. commonly used…

General view of chemist George Wieczorek (left) and an unidentified chemist using a Geiger counter to measure ionizing radiation in radioisotopes at an unidentified U.S. Department of Agriculture facility. A box of…

General view of granulation equipment used at the U.S. Department of Agriculture's Agricultural Engineering Laboratory located in Beltsville, Maryland. This equipment is believed to have been used by chemist John O.…

General view of the indoor soil track used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. Measuring 9 feet wide by 70…

Three views of the Engine Room at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. showing assorted machinery and apparatus.

The Fixed Nitrogen Research Laboratory…

Close-up view of the interior of an apparatus likely used for the manufacture and/or testing of fertilizer at an unidentified U.S. Department of Agriculture facility.

General view of an International Fertilizer Distributor (No. 49 Machine) in use at the U.S. Department of Agriculture's Plant Industry Station facility in Beltsville, Maryland. This machine was used to determine the…