6 MISC. PUBLICATION 9 9 2, U.S. DEPT. OF AGRICULTURE 



indentations, and rolled or bounced along the surface. On fresh 

 gopher mounds or on loose, recently plowed soil, the pellets bounced 

 or rolled except when they hit the surface at an angle of about 90°. 

 Even then they did not bury themselves and could still be seen par- 

 tially embedded in the loose soil (Wagner, 1949). 



It has also been claimed that the soil in compressed earthen pellets 

 would provide covering for the seeds. Observations in Idaho revealed 

 that as pellets were moistened by rains, the soil covering softened and 

 spread out into a rounded mound, and the seeds were usually left with 

 little or no covering. The disintegrated pellet mound was exposed 

 and more susceptible to rapid drying than the surrounding soil 

 surface. 4 



Coated Seed Pellets 



Coated seed pellets were developed to aid in attaining even distribu- 

 tion of small vegetable and flower seeds. These pellets are designed 

 to be sown at the same depths recommended for nonpelleted seed. 

 Coated pellets of sugar beet seeds were first made commercially during 

 World War II. In 1949 and 1954 coated seed pellets of crested 

 wheatgrass and intermediate wheatgrass were used for seeding large 

 range areas in Idaho by airplane. 



Manufacture and composition 



Coated seed pellets are made by building up a coating of numerous 

 layers around the seeds as they are tumbled in a slowly revolving 

 drum. There are two common types. One has a coating of clay; 

 the other is coated with finely powdered feldspar and other materials 

 bonded with a plastic adhesive. The seeds are shipped to a central 

 plant for coating. Small amounts of fertilizers, growth stimulants, 

 growth hormones, fungicides, insecticides, and rodent repellants are 

 often added and the alkalinity of the coating can be controlled 

 (Westrin, 1948; Rudolf, 1949; Gatherum, 1951; Carolus, 1954; Nissley, 

 1955; Hull, 1959). 



Description 



Coated seed pellets are the same general shape as the seed itself, but 

 somewhat larger (figs. 2 and 3). A seed or some other piece of plant 

 material forms the nucleus of each pellet. Seed lots of high purity 

 normally have one seed per pellet. Trashy seed has less. Pellets of 

 crested wheatgrass often contain more than one seed. Tisdale and 

 Piatt (1951) found an average of 1.3 seeds of crested wheatgrass per 



4 Unpublished data from the Intermountain Forest and Range Experiment 

 Station, Ogden, Utah. 



