Agriculture Reference
In-Depth Information
tolerance for 98.40% is 0.47 (from Table 13.2) (0.93%/2). When this is added to the tolerance for the luo-
rescence test result, the total tolerance is 5.05 (0.45 + 4.6 = 5.07). This tolerance is applied by giving both
tests an equal chance to be correct and multiplying by the percentage purity (100% - 10%)/100% - 0%) ×
98.40%) to give 88.56% perennial ryegrass. The tolerance is then applied to 88.56% or 9.84% as the case
may be. These calculations are provided in the AOSA rules.
The application of these tolerances to a component of the purity test, e.g., the chemical test for sweet
clover, is illustrated by the following example:
A 400-seed examination of a seed lot with 98.76% sweetclover shows 92% (368 seeds) olive
or yellow-green (white sweetclover) and 8% (32 seeds) stained dark brown or black (yellow
sweetclover).
a. The tolerance for 92% olive or yellow-green seeds for a 400 ⁄ 400 seed test is 3.4%. One-
half the pure seed tolerance (Table 13.2, column C) for 98.76% is 0.33. 3.4 is added to
0.33% (one-half the pure seed tolerance for 98.76%) to give 3.73%.
b. The tolerance for 8% dark brown or black seeds in a 400 ⁄ 400 seed test is 4.2%. This is
added to 0.33% (one-half the pure seed tolerance for 98.76%) to give 4.53%.
The tolerance is then applied by irst determining the percentage of white sweetclover (92% ×
98.76% = 90.86%) and yellow sweetclover (8% × 98.76% = 7.90%), with a tolerance of 3.73%
and 4.53%, respectively.
Finally, the tolerance table can be applied to other cases, such as the percentage of different vari-
eties (within a kind) present in a seed lot.
For example, the pure seed content in a sample of Kentucky bluegrass is 88.65%. Further exami-
nation of a 1,000-seed subsample shows 928 seeds were the kind indicated on the label and 72 of
other kinds or varieties. The 928 seeds were calculated to be 93.40% of the pure seed by weight
(928 ⁄ 1,000 × 100% = 92.8%).
The tolerance for 92.8% for 100 seeds (1,000 ⁄ 400 column) is 2.8%. One-half the pure seed toler-
ance (for chaffy grass) for 82.80% is 1.10%. This is added to the tolerance above to give the total
tolerance of 3.90% (1.10% + 2.80% = 3.90%).
The tolerance is applied to the total percentage of Kentucky bluegrass in the sample (88.65 ×
93.40 ⁄ 100 = 82.80%), so the total tolerance is applied to 82.80%. For more details refer to Sec.
13.4, AOSA rules, 2010.
Table 13.17 gives AOSA tolerances for fungal endophyte tests when results are based on 30 to 400
seeds, seedlings, or plants in a test. In principle, these tolerances are identical to those in Table 13.17 when
a 400-seed test is made, but tolerances are also given for as few as 30-seed tests. Both recognize only
random sampling error
and are not based on actual test results as most other AOSA and ISTA tolerances.
Their similarity is based on the nature of the decision-making process. Individual decisions are made for
each seed. Does it contain endophyte (yes or no)? Does it luoresce (yes or no)? Does it represent the cor-
rect variety (yes or no)? Is it sweetclover (yes or no)? Both are similar to the decision process in evaluating
germination. Has germination occurred (yes or no)? Although in principal, AOSA germination tolerances
(Table 13.6) should be identical to those for endophyte and luorescence, germination tolerances were
adopted as early as 1917 and account for sources of experimental error other than random sampling error.
