THE TESTING OF SEEDS

The Science of Seed Testing

OREN L. JUSTICE.

ADULTERATION of seed used to be fairly common. Crop seeds were mixed with other kinds of less expensive seed or inert material so like the desirable seed that they were hard to detect.

Some European seedsmen screened and stained sand to the size and color of clover seeds, with which they mixed it. Expensive seeds, such as cauliflower, were adulterated with less expensive kinds that could not be distinguished by seed characteristics. Factories existed in England in which the adulterants were devitalized to avoid detection. To stop them, Parliament adopted the Adulterated Seeds Act in 1869.

We have many records of seed adulteration in the United States during 1890-1915. Common examples include sweetclover and black medic in alfalfa and red clover; Canada bluegrass in Kentucky bluegrass; and perennial ryegrass in meadow fescue or vice versa, depending on the difference in prices.

Screenings containing relatively high percentages of weed seeds were frequently used as adulterants.

Seeds of dodder, a parasitic pest, were such a common impurity in forage seeds that western European countries, Canada, and Argentina legislated against the practice. An examination of 873 samples of red clover and alfalfa seed by the Federal seed laboratory in 1906 showed that 30.6 percent of the samples contained dodder.

Analyses of 61 samples of low-quality red clover seeds imported into the United States in 1905 and 1906 revealed averages of 30 kinds of weed seeds per sample, 3,088 weed seeds per ounce, 74 percent of pure seed, and dodder in 75 percent of the samples.

The sale of low-germinating seeds or dead seeds in Europe and America added to the uncertainties of crop production. The average germination of 12,454 packets of vegetable seeds collected from commission boxes and tested by the Federal seed laboratory in Washington from 1907 to 1910 was 60.5 percent. Mail-order seed was somewhat better; 6,117 samples purchased in 1911 gave an average germination of 77.5 percent.

These and other unscrupulous practices stimulated the study of seeds in many countries and States and led to the establishment of laboratories where seeds could be tested.

THE FIRST STATION for testing seed was established at Tharand in Saxony, Germany, in 1869, under the direction of Friedrich Nobbe.

E. Moller-Holst was planning a private seed-testing station in Copenhagen, Denmark, at the same time. It opened in 1871 and later was supported by public funds. By 1904, there were more than 130 seed-testing stations outside the United States.

Some farsighted men in the United States saw the need and began studies and examinations of seeds before the adoption of seed laws or establishment of seed laboratories.

The first laboratory for the examination of seed in this country was established at the Connecticut Agricultural Experiment Station in 1876 by E. H. Jenkins, who had studied in Germany and spent some time with Dr. Nobbe.

Seed testing was well established by 1900 in the U.S. Department of Agriculture, Connecticut, Maine, Massachusetts, Michigan, New York, and Vermont. Within the next 10 years, at least 10 other States were testing seeds. The Federal laboratory gave impetus to this movement by the establishment of several cooperative Federal-State laboratories in the South, Middle West, and Far West.

Forty-four States were operating seed-testing laboratories in 1930. Two more opened laboratories by 1941. Three States have found it more economical to have their samples tested by other laboratories on a fee basis than to maintain their own facilities.

Now there are well-equipped laboratories with trained personnel to test seed for purity, germination, seeds of noxious weeds, and moisture content. Several laboratories are prepared to make variety tests for control purposes.

A few conduct tests for designated disease organisms.

FACTORS of seed quality include: Percentages of pure seeds, other crop seeds, weed seeds, and inert matter; percentages of germination and hard seeds when present; the rate of occurrence of designated seeds of noxious weeds; varietal purity; freedom from disease and disease organisms; moisture content; origin of production; and test weight (the bushel weight, hectoliter weight, 1,000-seed weight).

The chief aim in testing seeds is to assess the value of each sample or lot of seeds tested in accordance with the quality factors. Successful testing for them requires adequate facilities, a trained staff, uniform methods or procedures, and a research program that looks to the improvement of methods and procedures.

In developing standard testing procedures, primary consideration is given to providing methods by which accurate and reliable information may be obtained. This is essential if the test results are to be of value to the planter.

The second consideration is to provide methods by which uniform results may be obtained.

Because seed is a commodity of commerce, the testing procedures have to be standardized to the extent that results obtained on a sample in one laboratory can be repeated within accepted tolerances by another laboratory. Whether the original test is made by a private, commercial, State, or Federal analyst, the seed lot maybe tested again in a distant State or in a foreign country. Financial transactions in seed, movement of seed in domestic and international commerce, and administration of seed laws would be greatly handicapped without confidence in the test results.

Finally, the methods must be practical. The degree of accuracy and uniformity of the results and the number of samples that can be tested are limited by the equipment and amount of work required in making the test, the number of days before the results are available, the kind of seed, and how well the seeds have been cleaned.

THE METHODS of testing seeds have been published under different titles and by various institutions and organizations and are referred to as rules.

The first rules in North America were prepared and published in 1897 in a circular entitled, "Rules and Apparatus for Seed Testing," by the Department of Agriculture as unofficial guides for seed analysts.

They specified the minimum size of samples for purity analysis and provided general instructions for making tests of germination. Equipment used for testing at that time was described and illustrated.

The publication was revised and expanded in 1904 to include methods of sampling seed lots, give more specific methods of testing for purity and germination, define the components of the purity analysis, and to specify the conditions for testing 63 kinds of agricultural and vegetable seeds for germination.

A group of persons from 16 States, the Department of Agriculture, and the Canada Department of Agriculture met in Washington, D.C., in 1908 to consider uniform methods of testing seeds and a model seed law. They formed an organization, which they named Association of Official Seed Analysts of North America. (It was shortened in 1939 to Association of Official Seed Analysts.)

One of the main functions of the association has been the preparation and adoption of official rules. Publication of the rules adopted by the association dates from 1917. Revisions since have been published by the New York Agricultural Experiment Station, the Department of Agriculture, and the association.

The Federal Seed Act of 1939 instructed the Secretary of Agriculture to develop and publish procedures for testing seeds to be used in the administration of the act. Consequently, appropriate procedures were published in 1940 as a part of the Rules and Regulations Under the Federal Seed Act.

Revisions were made in 1946, 1950, 1956, and 1960.

The commercial seed analysts, through their organization, the Society of Commercial Seed Technologists, also assist in the formulation of the rules. To avoid conflict between the two sets of rules, Federal employees take part in the development of the rules of the Association of Official Seed Analysts. The amendments adopted by the Association of Official Seed Analysts are then incorporated as far as possible into the regulations under the Federal Seed Act.

To take advantage of developments in seed testing, the rules have been revised at least every 5 years since 1940. Amendments and minor revisions can be made each year if necessary. The association maintains a standing committee to review research data and other information that may lead to improvement in the rules.

Members of the committee are persons from the State seed laboratories, the Department of Agriculture, the Canada Department of Agriculture, and the Society of Commercial Seed Technologists.

The International Rules for Seed Testing provide uniform methods of evaluating the quality of seeds moving in foreign commerce. These rules, first published in 1931 in English, French, and German, have been revised five times. Before 1950, there were some important differences between the North American rules and the international rules, but the major differences were compromised in 1953.

Many countries now use the international rules when testing for both domestic and foreign purposes. When requested, seed-testing stations belonging to the International Seed Testing Association sample seeds intended for foreign commerce and test the samples by the international rules for the issuance of certificates of quality.

MOST OF THE research on methods of testing seeds in this country has been done in the Federal seed laboratory and a few State laboratories, where testing is part of the agricultural experiment station or the agricultural college.

A research project on sampling and testing seeds was inaugurated by the Federal seed laboratory in 1948 under the Research and Marketing Act of 1946. Varying amounts of research on methods have been conducted since then in the Department. Much of the research conducted by the State agricultural experiment stations since 1956 has been coordinated on a regional basis.