Nov. 26 ,1917 
Field Technic in Rod Row Tests 
411 
It is entirely possible in a limited number of tests that if there is a 
competitive effect between adjacent rows that in some cases this might 
tend to lower the variability of the test. For example, if a plot hap¬ 
pened to be situated in a particularly favorable soil location, the rows 
would be expected to yield more than the average for that particular 
variety. If, in addition, the border rows of this plot grew near a much 
taller variety or beside a stronger foraging variety, the effect of compe¬ 
tition would be to lower the yield and thus reduce the calculated coeffi¬ 
cient of variability for the variety in question. For this reason the 
coefficient of variability for the yield of the central rows is compared with 
the most variable border row test. Results of such comparisons are 
given in Table IX. The probable error of the difference between coeffi¬ 
cients of variability being calculated by the following formula, the error 
of a difference is equal to the square root of the sum of the squares of the 
quantities entering into the difference (£). 
Table) IX.— Comparison of the difference between the coefficient of variability of the 
border and central rows 
Cereal. 
Designation of test. 
Difference be¬ 
tween the coeffi¬ 
cient of variability 
of the border 
and central rows. 
Difference 
-*■ prob¬ 
able error. 
Wheat (Minnesota 169). 
Plant Breeding Nursery.... 
2. 09 ±1. 788 
I. 2 
Do. 
Farm Crops variety test .... 
1. 35 ±1.390 
•9 
Oats (Minnesota 281). 
Plant Breeding Nursery. 
3. 93±i. 230 
3-2 
Do. . . 
Farm Crops variety test .... 
2. 641b 1. 613 
1. 6 
Barley (Minnesota 105). 
Plant Breeding Nursery. 
10. 91 ±4. 208 
2. 6 
Do. 
Farm Crops variety test .... 
3 - 63 ±i- 3 86 
2. 6 
Winter wheat (Minnesota 529) 
Plant Breeding Nursery. 
2. 74-ibi. 509 
1.9 
Do. 
Farm Crops variety test_ 
• 94 ±i. 838 
*5 
The results show no significant difference for the spring- and winter- 
wheat tests between the coefficients of variability of border and central 
rows. The chances against an occurrence of a deviation as large as 1.9 
times the probable error as obtained in the Plant Breeding winter-wheat 
test is 4.00 to 1. For barley the odds against an occurrence of a devia¬ 
tion as large as 2.6 times the probable error, as obtained for both Farm 
Crops and Plant Breeding tests, is 11.58 to 1 (9). The odds against an 
occurrence as great as 1.6 and 3.2 times the probable error as obtained 
for the Farm Crops and Plant Breeding tests for oats are, respectively, 
2.57 to 1 and 31.36 to 1. It seems fair to conclude that border rows 
are more variable than central rows for barley and oat tests and that the 
differences in variability of border and central rows of spring- and winter- 
wheat tests here reported are of no great importance. 
The comparison between the coefficients of variability for the 3-row 
plots and central rows is a means of determining the value of plot size. 
The results would seem to be more significant in the case of spring and 
