SHAPE AND SIZE OF PLOTS IN TESTS OF VARIETIES OF GRAIN. 83 



compared wpth the varieties already established. Of course a 

 check on the productivity of new varieties may be bad by plant- 

 ing several plots to one commercial variety regnlarly distributed 

 throughout the field. Even with this, an additional means of 

 gauging the value of a new strain would be advantageous. The 

 importance of the size and shape of a plot impresses one 

 forcibly when it is considered that marginal plants may 

 yield twice as much as plants within the plot. In this event any 

 yield of a variety grown on 50th acre units would have to be 

 considered as 106.7 percent, on a looth acre 109 percent, on a 

 loooth acre 128 percent according to figures given in Table 2. 



In oblong plots of these unit areas the percent would be much 

 higher. 



This problem of the influence of size and shape of plots on the 

 results of variety tests of grain may be viewed from the stand- 

 point of marginal drill length in comparison with the total drill 

 length in a plot. In this the plants within six inches of the bor- 

 der at each end of a drill are considered subject to the conditions 

 outside the margin and, hence, make up a row across each end 

 of the plot. 



In terms of x, x representing the side of a square, a unit area 

 x^ in different rectangular shapes will have the dimensions given 

 in Table 4 Also one will note in this table the length of the 

 marginal drills and the total drill length together with the rela- 

 tion between marginal drill length and total drill length. 



Table 4. 

 Relation of Marginal Drill Length to Total Drill Length. 







Length 2 



Length 4 



Length 8 



Length 16 



Shape of Plot. 



Square. 



times 



times 



times 



times 







width. 



width. 



width. 



width. 



Area 



a;2 



a;2 



a;2 



X 



a;2 



a;2 



X 



Width in feet 



X 



0.7071a; 



2 



X 



. 3536a; 



4 



X 



Length (of rows) in feet 



X 



1.4142a; 



4— 

 2 



2.8284.T 



16— 

 4 



Total number of drills of x 











X 



length in feet i ft. apart 



2x 



1.4142a; 



X 



.7071a; 



2 



2a;2 



Total length in feet of all drills. 



2x2 



2a;2 



2x2 



2a;2 



Length in feet of marginal drills 



4a:-2* 



4.2426X-2 



hx-2 



6 . 364a;-2 



8 . 5a; -2 



Ratio of marginal drill length to 



2a;-l 



2.1213a;-l 



2.5X-1 



3.182X-1 



4.25a;-l 



total drill length 













X- 



X- 



a;2 



a;2 



a;2 



* In a plot in which the drills are spaced six inches apart two feet must be subtracted 

 rem the periphery to avoid duplication of drills in the corners. 



