80 MISC. PUBLICATION 4 3 4, IT. S. DEPARTMENT OF AGRICULTURE 



seeded species, can be cut in half because of the better moisture control 

 that can be maintained. 



Knowing the germination percentage and the ultimate stand desired 

 per lineal foot for each species, it is possible to compute the number 



1 host? 



of seed to sow per lineal foot by the following formula: N= — p — > 



wherein N= number of seed to sow per lineal foot; S= ultimate stand 

 desired; P=germination percent of the seed; and R = sowing ratio. 

 For example, if a stand of 6 seedlings per lineal foot is selected as the 

 optimum density for a particular species, and if the seed has a germina- 

 tion of 50 percent and the sowing ratio of 4:1, the formula then becomes 



A/=10 ^ )X6X4 ^48, the number of seed to sow per lineal foot of drill, 

 ou 



Given the number of seed per pound and the lineal feet of row per acre, 



a supplementary formula of value for expressing the number of seeds 



sown per foot of drill in pounds of seed needed per acre is A=-^j , 



wherein A = pounds of seed needed per acre; N= number of seeds sown 



per foot of drill; M ^number of thousands of seed per pound ; and F= 



number of thousands of lineal feet of row per acre. For example, if 48 



seeds are to be sown per lineal foot and the rows are to be 2 feet apart 



(21,780 lineal feet of row per acre) and there are 26,000 seed per pound, 



48 X 21 78 

 the formula becomes A = rr- 1 - =40.2 pounds of seed needed per 



acre. 



If adequate seed supplies are available, the safest procedure is to 

 sow heavily enough to obtain stands slightly in excess of optimum 

 density and after the seedlings are well established to thin down to 

 the desired final stand. This is especially desirable for certain species 

 which are difficult to establish. Costs per thousand of growing 

 seedlings are virtually in an inverse proportion to the percent of stand, 

 i. e., a 50-percent stocking will practically double the cost per thou- 

 sand of that in a 100-percent stand. Therefore, the cost of the seed 

 used in oversowing and of the labor involved in thinning is well justi- 

 fied within reasonable limits. Briggs has obtained data showing that 

 percent of emergence of seedlings decreased consistently as rate of 

 sowing increased, owing apparently to such factors as increased 

 damping-ofT and competition for available moisture in the denser 

 sowing. 



Sowing Methods 



The method of sowing seed is secondary in importance to the factors 

 of season, density, and depth of sowing. Emphasis should be placed 

 on obtaining even distribution of seed and uniform depth of cover. 

 With hard, dry seeds of spherical or ovoid shape, uniform distribution 

 can easily be assured by mechanical drill sowing, the seeders being 

 hooked up in multiple. However, not all of the tree species grown for 

 plains planting lend themselves readily to machine sowing because of 

 shape and size of seed, or pretreatment. No satisfactory mechanical 

 sower is available that will sow all the types of seed in 2- to 3-inch 

 bands. 



Because of the lack of a suitable mechanical sower, nurserymen in 

 the plains region have relied upon hand sowing of some seed to secure 

 even distribution in the bands. This method (fig. 23) necessitates 





