Direct seeding short-lived solution


Longleaf pine forests of Louisiana and East Texas were particularly devastated during the “golden age of lumbering” in the early 20th century as companies used steam-powered logging equipment, which provided a challenge to foresters: How to return millions of acres of cutover pine into forests.

When the Alexandria Research Center of the U.S. Forest Service, Southern Forest Experiment Station was established after World War II, almost 5 million acres of forestland in the two-state area were in the need of reforestation.

The Research Center’s assignment was to develop technology to return this cutover land to plush forests that once blanketed the area.

It was estimated that if this treeless longleaf pine land was reforested by planting nursery grown seedlings, the job would take 50 or more years at the rate feasible with the then current nursery capability. There was a significant need to develop additional technology to meet this awesome reforestation project. Although expanding bareroot nursery capacity was an obvious goal, another option was development of a direct seeding capability.

Sowing of tree seeds on prepared forests soils was often considered and tried — and sometimes the trials met with success. In l920, the Great Southern Lumber Co. at Bogalusa hand seeded slash pine on furrows plowed by teams of mules. An 800-acre tract was successfully regenerated. The company’s ranger, F.O. “Red” Bateman, was responsible for this successful seeding.

Following attempts failed and Bateman was quoted as describing his evaluation of the potential of direct seeding as: “When we went out to start seeding, there was a pheelock (field lark or meadowlark)sitting’ on a fence, he whistled, and up come 50 more pheelocks. We went down the furrows, dropping longleaf seeds every six feet. The pheelocks followed us down the furrows, and, gentlemen, when we got to the end, there wasn’t a damn thing left in the furrows but bird s_ _ _!”

Harold Derr, the research forester assigned to task of developing direct seeding, justified it by the technique being fast and requiring minimum labor, significantly cheaper than planting, it provided denser stands—at the time planting success was poor, and it could take advantage of bumper seed crops. The storage of longleaf pine seed was then problematic.

Early in the evaluations of direct seeding, predator control by men patrolling with shot guns was the only practical method of reducing losses to birds — mostly flocks of migrant species. The open grassland of the cutover forests favored the development of large flocks of species such as meadowlarks.

Rodent Repellents

In the mid-1950s, tests began to find a chemical when applied to seeds would protect them from bird predation. Anthraquinone was found to be a good repellent. It was found to be environmentally safe and is used in numerous compounds such as dyes, laxatives, and cosmetic products. Soon afterwards, the chemical Thiram was found to be equally effective. Thiram is also registered as a fungicide formulation used as a seed treatment to control seedborne microorganisms. Thiram was found to have some rodent-repellent qualities and replaced anthraquinone as the preferred seed treatment. Both chemicals were registered as a seed treatment for bird repellency.

Although early studies found that birds were the primary predators of pine seeds, fall sowing of longleaf pine seeds frequently resulted in heavy rodent predation because their populations increase during the winter and spring. Tests then begin to find chemicals that would reduce the losses from rodents—primarily field mice.

Although Thiram provide some protection from rodents, adding the chemical Endrin greatly improved seeding success. Endrin was mainly sold as an insecticide and was a potent chlorinated hydrocarbon poison and presented a hazard to the environment and animal life. The use of Endrin was justified because only a half of a pound of active ingredient was applied to 100 pounds of seeds distributed over up to 40 to 50 acres.

There was some question of whether Endrin was truly a repellent or if it killed the rodents that ate the seeds. Evaluations seemed to confirm the hypothesis that rodents ate some of the treated seeds, became sick and then avoided continued predation.

In the early 1970s, however, public concern about the use of many extremely toxic chemicals in agriculture caused the Environmental Protection Agency and Department of Agriculture to review the registration of such chemicals. Although the continued use of Endrin in direct seeding was accepted, other uses were not approved, and the chemical was withdrawn from the market in the United States. No other chemical with rodent repellency for treating pine seeds has been registered.

Guidelines for use of seeding

The guidelines necessary for successful direct seeding are: prepare the site so seeds can fall on mineral soil; sow seeds treated with bird and rodent repellents; stratify or prechill seeds, other than longleaf pine, prior to sowing in the early spring following an inch or more of rain; sow longleaf in either fall or spring — these seeds will germinate in the fall after sowing; and sow at a rate depending upon type of application.

The rate of sowing depends largely on the method of distributing seed. For broadcast sowing, the rate for all species should be about 10,000 to 15,000 viable seeds per acre. About half this quantity is needed for furrow seeding. Disk seeding requires bout 7,000 to 12,000 seeds per acre.

Although the technique was originally developed for broadcast seeding by aircraft, stands were frequently overstocked and needed precommercial thinning. To deal with this problem, the application techniques were then adapted to row seed by tractors or to seed strips disked by tractors.

Methods were developed to sow by hand, hand-operated cyclone seeders, airplanes, helicopters or tractor-drawn machines. For large operations, up to 1,500 acres per day can be sown by light planes and a helicopter can sow 3,000 acres. Smaller operations can best be seeded by one of the more labor-intensive methods.

Seeded stands are more susceptible to drought and early competition pressure than are planted stands. A systematic inventory of seedling survival should be done at the end of the first and second growing season. A successful seeding is one where losses are minimized so that adequate first-year survival is achieved using the least amount of seeds. The landowner must have a reliable estimate of controllable losses, achievable stand density and losses from uncontrollable factors such as drought.

Current status

Direct seeding has been used to successfully regenerate several million acres of southern pines beginning in the late 1950s and into the late 1970s. Gradually as the large backlog of cutover land was reforested, using the direct seeding method declined. Landowners learned that seeding was not as reliable as planting of seedings, resulting stand density was frequently too high and caused a need for precommercial thinning and the technique did not allow for the use of developing tree-improvement technology.

Further complicating its use is the shift in weather patterns over the past 50 years. Recent evaluations of drought severity during the fall and winter months, when seeding should occur, indicate that drought severity is now significantly higher than in the years when the technology was developed. This is another reason that direct seeding is now seldomly used — its use is less frequently successful.

Direct seeding is primarily limited to restoration of large forested areas destroyed by wildfires or where it is not economically feasible to plant more expensive nursery stock.

Regardless of future use, direct seeding was developed and applied to meet a specific need — reforestation of massive areas of cutover forestland. Direct seeding met a significant need at the time — millions of acres of devastated forest land were put into production.

For those interested in the specifics of direct seeding, see Barnett’s 2014 document, “Direct seeding southern pines: history and status of a technique developed for restoring cutover forests” https://www.srs.fs.usda.gov/pubs/gtr/gtr_srs187.pdf.

(Dr. Jim Barnett is emeritus scientist for the U.S. Forest Service.)

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