PELLET SEEDING OX WESTERN RANGELANDS 3 



SEED PELLETS 



The manufacture and characteristics of the three types of seed 

 pellets for seeding rangelands follow. 



Compressed Earthen Pellets 

 Manufacture and composition 



Compressed earthen pellets are manufactured by a machine con- 

 sisting of four gearlike wheels with a series of quarter-spherical 

 depressions around the rim. The four wheels meet at a common 

 point and mesh so that the seed-and-soil mixture fed into the machine 

 is pressed from four sides to form a spherical pellet. The wheels 

 exert considerable pressure in forming the pellets. Seemingly dry 

 soil is made into extremely hard pellets. The normal density of 

 uncompressed clay soil in Idaho is about 100 pounds per cubic foot. 

 Compressed pellets have densities one-third to three-fifths greater 

 than normal (Tisdale and Piatt, 1951). 



Pellets are made with soil on or near the seeding site. Clay loam 

 of low moisture content is preferred. Soil that contains quartz par- 

 ticles or other abrasive material causes rapid wear on the machines. 

 This results in poor pellets; they become larger with machine wear 

 and in extreme cases come out of the machine as connected "strings." 

 Tisdale and Piatt (1951) observed at one stage of a pelleting opera - 

 ation that "half or more of the processed material passed through 

 the equipment either totally unpelletized or so loosely incorporated 

 that it disintegrated in screening or other handling." When the 

 soil is too moist or has a high percentage of coarse particles, pellets 

 are not firm and they fragment readily in handling (Wagner. 1949 



Description 



The size of the compressed pellet depends on the size of the seed 

 and ranges from %-ineh diameter for small seeds to Vincli or more 

 for larger seeds (fig. 1). The number of pellets ranges from 1,450 

 to 1,880 per pound for the K-inch size and from 420 to 630 tor the 

 %-inch size (Wagner, 1949; Bleak and Phillips, 1950). Some char- 

 acteristics of pellets used in the 1948 Manti-LaSal seeding are given 

 in table 1. 



Seeds per pellet average from 5 to 10. but imperfect mixing causes 

 variations in the number in each pellet. Examination o( pellets from 

 many projects has shown a range of from none to 59 seeds per pel- 

 let and averages for different species of from 3.6 to 28 seeds per 

 pellet. For crested wheatgrass from several projects, the average 

 number of seeds per %-inch pellet ranged from 7.5 to 20 (Allen, 

 1948; Stevenson, 1949; Bleak and Phillips. 1950: Tisdale and Piatt. 



