#### § 201.51a Special procedures for purity analysis.

(a) The laboratory analyst shall use the Uniform Blowing Procedure described in this paragraph to separate pure seed and inert matter in the following: Kentucky bluegrass, Canada bluegrass, rough bluegrass, Pensacola variety of bahiagrass, orchardgrass, blue grama, and side-oats grama.

(1) *Separation of mixtures.* Separate seed kinds listed in this section from other kinds in mixtures before using the Uniform Blowing Procedure.

(2) *Calibration samples.* Obtain calibration samples and instructions, which are available on loan through the Seed Regulatory and Testing Division, S&T, AMS, 801 Summit Crossing Place, Suite C, Gastonia, North Carolina 28054.

(3) *Blowing point.* Use the calibration samples to establish a blowing point prior to proceeding with the separation of pure seed and inert matter for these kinds.

(i) Refer to the specifications on the calibration samples for Kentucky bluegrass, orchardgrass, and Pensacola variety of bahiagrass to determine their appropriate blowing points for the Uniform Blowing Procedure.

(ii) Use the calibration sample for Kentucky bluegrass to determine the blowing points for Canada bluegrass, rough bluegrass, blue grama, and side-oats grama.

(A) The blowing point for Canada bluegrass shall be the same as the blowing point determined for Kentucky bluegrass.

(B) The blowing point for rough bluegrass shall be a factor of 0.82 (82 percent) of the blowing point determined for Kentucky bluegrass. The 0.82 factor is restricted to the General-type seed blower.

(C) The blowing point for blue grama shall be a factor of 1.157 of the blowing point determined for Kentucky bluegrass. Before blowing, extraneous material that will interfere with the blowing process shall be removed. The sample to be blown shall be divided into four approximately equal parts and each blown separately. The 1.157 factor is restricted to the General-type seed blower.

(D) The blowing point for side-oats grama shall be a factor of 1.480 of the blowing point determined for Kentucky bluegrass. Before blowing, extraneous material that will interfere with the blowing process shall be removed. The sample to be blown shall be divided into four approximately equal parts and each part blown separately. The 1.480 factor is restricted to the General-type seed blower.

(4) *Blower calibration.* Calibrate and test the blower according to the instructions that accompany the calibration samples before using the blower to analyze the seed sample. Use the anemometer to set the blower gate opening according to the calibration sample specifications.

(i) Determine the blowing point using a calibrated anemometer.

(ii) Position the anemometer fan precisely over the blower opening, set it at *meters per second* (m/s), run the blower at the calibrated gate setting, and wait 30 seconds before reading the anemometer.

(iii) Use this anemometer reading to determine the blower gate setting whenever the Uniform Blowing Procedure is required.

(5) *Pure seed and inert matter.* Use the calibrated blower to separate the seed sample into light and heavy portions. After completing the initial separation, remove and separate all weed and other crop seeds from the light portion. The remainder of the light portion shall be considered inert matter. Remove all weed and other crop seeds and other inert matter (stems, leaves, dirt) from the heavy portion and add them to the weed seed, other crop seed, or inert matter separations, as appropriate. The remainder of the heavy portion shall be considered pure seed.

(b) The Multiple Unit Procedure of determining the pure seed fraction shall be used only for the kinds included in the following table when multiple units are present in a sample. These methods are applicable to the kinds listed when they occur in mixtures or singly. Any single unit without attached structures, as described below, shall be considered a single unit. Multiple units and single units for the kinds listed shall remain intact. The attached glumes and fertile or sterile florets shall not be removed from the fertile floret.

(1) A multiple unit is a seed unit that includes one or more structures as follows (the length of the awn shall be disregarded when determining the length of a fertile floret or an attached structure):

(i) An attached sterile or fertile floret that extends to or beyond the tip of a fertile floret;

(ii) A fertile floret with basally attached glume, glumes, or basally attached sterile floret of any length;

(iii) A fertile floret with two or more attached sterile and/or fertile florets of any length.

(2) Procedure for determination of multiple units:

(i) For the single kind: determine the percentage of single units present, based on the total weight of single units and multiple units. Apply the appropriate factor, as determined from the following table, to the weight of the multiple units and add that portion of the multiple unit weight to the weight of the single units. The remaining multiple unit weight shall be added to the weight of the inert matter.

(ii) For mixtures that include one or more of the kinds in the following table, determine the percentage of single units, based on the total weight of single units and multiple units, for each kind. Apply the appropriate factor as determined from the following table, to the weight of multiple units of each kind.

Table of Factors To Apply to Multiple Units a

| Percent of single units of each kind | Crested wheat-grassb | Pubescent wheat-grass | Intermediate wheat-grass | Tall wheat-grassc | Western wheat-grassc | Smooth brome |
| --- | --- | --- | --- | --- | --- | --- |
| 50 or below | 70 | 66 | 72 | | | 72 |
| 50.01-55.00 | 72 | 67 | 74 | | | 74 |
| 55.01-60.00 | 73 | 67 | 75 | | | 75 |
| 60.01-65.00 | 74 | 67 | 76 | | | 76 |
| 65.01-70.00 | 75 | 68 | 77 | | 60 | 78 |
| 70.01-75.00 | 76 | 68 | 78 | | 66 | 79 |
| 75.01-80.00 | 77 | 69 | 79 | 50 | 67 | 81 |
| 80.01-85.00 | 78 | 69 | 80 | 55 | 68 | 82 |
| 85.01-90.00 | 79 | 69 | 81 | 65 | 70 | 83 |
| 90.01-100.00 | 79 | 70 | 82 | 70 | 74 | 85 |
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| a The factors represent the percentages of the multiple unit weights which are considered pure seed. The remaining percentage is regarded as inert matter. | | | | | | |
| b Includes both standard crested wheatgrass and fairway crested wheatgrass. | | | | | | |
| c Dashes in table indicate that no factors are available at the levels shown. | | | | | | |

[[59 FR 64498](https://www.federalregister.gov/citation/59-FR-64498), Dec. 14, 1994, as amended at [85 FR 40581](https://www.federalregister.gov/citation/85-FR-40581), July 7, 2020]