Proc. 57th Southern Pasture and Forage Crop Improvement Conference, Athens, GA April 23-25, 2002
Coatings for Legume and Grass Seed
Joe Burns, Brad Bennett, Kelly Rooney,
John Walsh and Jeff Hensley
CelPril, Manteca, CA
The widespread use of seed coatings is relatively new, within the last 20 years, although some primitive form of seed coating has been practiced for many years by putting rice seed inside a mud ball. The mud balls were spaced evenly in a flooded rice paddy and the rice plants root as the mud ball holds the rice seed in position. This eliminated the problem of seed drift when the dry rice seed was sown on the surface of flooded paddys.
By 1958 there were 35 patents that proposed different types of coatings and processes to apply them. One patent, 1866, was to put a paste of wheat flour on cotton seed to slick down the lint whereby the seed would flow in the planter. In 1905, Aristotle Rey received a patent to use glue to stick fertilizer to cereal seed. Evidently these seed coatings weren’t accepted by the farmers.
In the late 1950’s, New Zealand Agricultural workers developed a coating for clover and grass seed. These coated seeds could be broadcast by airplane in the rugged hills of New Zealand. The use of coated seed proved to be highly successful in establishing economical stands of clover and grass due to improved inoculation and ballistics.
The coating was put on clover seed to hold the inoculum, help give a uniform seeding pattern and also to provide a micro-environment for quick and effective nodulation. The grass seed were coated to help with a uniform seeding pattern and to provide added weight to insure good seed to soil contact.
Meanwhile back in the U.S., Ramsey Seed Inc. of Manteca, CA took the lead on the national scene and started a coating and pelleting operation in 1968 called Cal-Kote. Bill Ramsey and his son, Jim, made a number of visits to New Zealand to evaluate their coating technology. In 1973, Ramsey Seed negotiated the exclusive rights for the New Zealand process in the U.S., That same year, Ramsey Seed formed a separate seed coating operating unit called Prill-Kote Inc. In 1974, Northrup King developed a continuous coating process for small seeded legumes called Noculime.
As early as 1960, there were seven companies which were preinoculating legume seed, but didn’t put a coating on them to protect the rhizobia (inoculum). This information came from a speech which Dr. Lewis W. Erdman, Principal Bacteriologist, USDA, gave to the American Seed Trade Association, January, 1961.
In 1975, Prill-Kote Inc. became CELPRIL INDUSTRIES and in 1986, CelPril launched Nutri-Kote, a seed coating for turf grasses, but also used on pasture and range grass seed.Nutri-Kote is a fertilizer coating which contains N, P, K, S, Zn, and Fe.
CelPril also developed Specialty Coatings for wild flowers, marigolds and shrunken sweet corn seed whereby the corn could be seeded with an air planter. In 1990, Rhone-Poulenc bought CelPril and with their interest in pesticides, much research is being conducted to gain the technology of applying both agri-chemicals and biologicals to seed.
After the inoculation coating for legumes and fertilizer coating for grasses, a new arena was opened by the film coating of vegetable seed to assist with the treating and planting of the seed of these crops. Also, with this new technology , insecticides and fungicides and weed control chemicals can be incorporated with the seed. A layer of film coating can be put on the seed to protect the seed. The pesticide can be applied to the seed and then a film coating can be wrapped around the seed to completely seal in the pesticide and reduced dust for worker and farmer safety. This complete seal of the pesticide gives excellent protection to the farmer or other user of the seed.
With the advent of pesticides which are needed in extremely small amounts (grams per 100 pounds of seed), this coating process will enable the application of precision amounts of these chemicals per seed. By 1995, several companies were coating seed in the U.S.
NOW LET’S TALK ABOUT COATING LEGUME AND GRASS SEED OF FORAGE CROPS. Just a few years ago in Tennessee, one of the big problems with estab1ishing alfalfa was poor inoculation. Many farmers were not doing a good job of inoculating the alfalfa seed. They were using old inoculum. letting the inoculum stay on the dash of their pickup truck in the hot sun which killed the inoculum. Also. some of them even forgot to use any inoculum. Then, too, there were the hot, dry seedbeds which also had a part in killing the inoculum. With the advent of coated seed just a few years ago and with the good judgement of seed dealers to supply these seeds, poor inoculation of alfalfa is now a rare happening in Tennessee.
There has been much discussion among researchers, extension specialists, the seed industry and farmers concerning the use of coated seed such as Rhizo-Kote XL at the same seeding rate (pounds per acre) as uncoated seed because the coated seed have about two-thirds the number of seeds per pound as uncoated seed.
The question was asked: Will the Rhizo-Kote XL seed produce an equal stand of alfalfa when compared to uncoated seed at the same seeding rate (pounds per acre)? With this question in mind, CelPril has conducted many “on-the-farm” strip tests comparing coated and uncoated seed in the Western, Midwestern and Eastern U.S. The data presented here is from Alabama, Kentucky and Tennessee, which is very similar to the data from the other areas of the U.S.
Fourteen field trials were conducted comparing Rhizo-Kote XL plus Apron* seed with uncoated, preinoculated plus Apron alfalfa seed at the same seeding rate. The Rhizo-Kote XL seed had about 33% fewer seeds per pound as compared to the uncoated seed. The preinoculated uncoated seed received the standard method of mechanical pre- inoculation. The average seeding rate was 18.5 pounds per acre for the Rhizo-Kote XL and 18.4 pounds per acre for uncoated seed. The alfalfa varieties used were Aggressor, Apollo Supreme and Amerigraze 401Z. The seed for the two treatments came from the same seed lot in order to eliminate genetic differences.
The two treatments in each strip test were planted at the same seeding rate per acre with the same machine and the machine was calibrated for each type of seed. The Rhizo-Kote XL seed flowed at a higher rate than the uncoated seed at the same machine setting.
All trials were planted in strips adjacent to each other. Fertilizer and lime were applied according to soil test recommendations. Seeding dates were near or within the recommended seeding dates of the respective Universities.
The soils were suitable for alfalfa and adequate stands were obtained on all strip tests.
Measurements made were “plants per square foot” on all trials and “stems per square foot” on six trials. About six weeks after planting, alfalfa seedling counts were made at twenty sites per treatment at each farm location. A one square foot wire frame was used to outline the area at each site and the plants inside the area were counted. Walking down the line between the treatments, the wire frame would be thrown into each treatment from the same spot in order to have as uniform soil conditions as possible for the two comparisons.
In the fall for spring seedings and in the spring for fall seedings, ten sites per treatment were dug and the plants per sq. ft. were put into a bucket and counted using the same procedure as described for the seedling counts site selection.
Of the fourteen strip tests conducted from 1993 to 2000, 2 were in Alabama, 3 in Kentucky and 9 in Tennessee.
*Apron, Registered Trademark of Syngenta.
The no-till method of planting alfalfa has been successful in establishing productive stands of alfalfa and CelPril wanted to know if Rhizo-Kote XL alfalfa seed would react the same way under no-till conditions as on prepared seedbeds. Five of the fourteen strip tests were conducted as no-till plantings.
The number of alfalfa stems per sq. ft. was also counted at six of the locations using the same procedure as for the seedling plant counts. Twenty sites per treatment were counted when the stand was well established and the regrowth after cutting had about a 12 inch canopy height.
The statistical analysis was performed using a standard two-way analysis of variance and least significant difference calculation based on the trial locations as treatment blocks.
Results and Discussion
Alfalfa plants and stems were counted per sq. ft. at 14 locations for plants and 6 locations for stems. The average number of seedling alfalfa plants per sq. ft. for the Rhizo-Kote XL seed was 33.59 and for the uncoated seed 35.38. The number of seed planted per sq. ft. for the RKXL treatment was 56.1 and for the uncoated 84.5, with about an 18.5 lb./acre at seeding rate average for both treatments and a 200,000 seed per pound number for uncoated seed used to calculate the number of seed per sq. ft .
The number of plants emerged as a percentage of the seed planted was 59.9 percent for the RKXL treatment and 41.9 percent for the uncoated. The RKXL data show that the number of plants per sq. ft. was equal to the uncoated and that the seed with the RKXL emerged at a significantly higher rate than the uncoated.
Table 1. Rhizo-Kote XL vs. Uncoated Preinoculated Alfalfa Seed Six Weeks after Seeding.
|
|
Uncoated |
Rhizo-Kote XL |
| Number of seed planted per sq. ft.* |
84.5 |
56.1 |
| Number of seedlings per sq. ft. ** |
35.38 |
33.59 |
| Percent emergence of seed planted |
41.9 |
59.9 |
14 locations in Alabama, Kentucky and Tennessee-1993-2000
* Average seeding rate, uncoated 18.4 lb/A, Rhizo-Kote XL 18.5 lb./A. 200,000 seed per pound.
** 280 measurements per treatment.
The same results were obtained when the alfalfa plants were dug and counted after the stand was well established. For the RKXL treatment, the number of plants per sq. ft. was 26.6 as compared to 27.8 for the uncoated, no significant difference. Again, when the comparison is made with the seed planted and the established plants per sq. ft., the RKXL had a higher percent of plants established as of the seed planted, 47.4 percent compared to the uncoated 32.9. For the Alabama and Tennessee locations, Rhizo-Kote XL had a significant higher survival rate (P = 0.05) and the Kentucky locations (P = 0.10).
Table 2. Five to Six Months after Seeding.
|
|
Uncoated |
Rhizo-Kote XL |
| Number of seed planted per sq. ft.* |
84.5 |
56.1 |
| Number of plants per sq. ft.** |
27.8 |
26.6 |
| Percent survival of seed planted |
32.9 |
47.4 |
13 locations in Alabama, Kentucky and Tennessee – 1993-2000
*Average seeding rate, uncoated 18.4 lb./A, Rhizo-Kote XL 18.5 lb./A. 200,000 seed per pound.
**130 measurements per treatment.
No-till planting compared to planting on a prepared seedbed showed the same relationships as above with RKXL 32.6 plants per sq. ft. and uncoated 33.8 on no-till. For the counts which were made on prepared seedbeds about six weeks after planting RKXL 34.2 and uncoated 36.2 plants per sq. ft.
Again, five to six months after seeding, there still was no significant differences in the number of plants per sq. ft. when no-till was compared to seeding on a prepared seedbed. Also, there were no significant differences between the RKXL and uncoated treatments.
Alfalfa stems per sq. ft. were counted on six of the strip tests to get some data comparing RKXL seed vs. uncoated seed. An average of 120 measurements per treatment showed 69.2 stems per sq. ft. for the RKXL treatment and 65.8 stems for the uncoated seed. The results show no significant differences between the treatments.
Table 3. Ten to Twelve Months after Seeding.
|
|
Uncoated |
Rhizo-Kote XL |
| Number of stems per sq. ft. * |
65.8 |
69.2 |
6 locations in AL, KY and TN. 1994-1995
*120 measurements per treatment
Research by Dr. Dennis Cosgrove and Dr. Dan Undersander in Wisconsin has shown a good correlation of alfalfa stems per sq. ft. with hay yields. They suggested that 55 stems per sq. ft. would produce maximum yield; that 40 stems per sq. ft. would result in a 25 percent reduction in yield and that 25 stems per sq. ft. would result in a 50 percent reduction.
There has been much discussion concerning the use of coated seed such as Rhizo-Kote XL at the same seeding rate as uncoated seed because the coated seed have about two-thirds the number of seed per pound as compared with uncoated seed.
These data and research findings and farmer experience have shown that excellent stands of alfalfa can be achieved with the same seeding rate of Rhizo-Kote XL seed vs. uncoated seed. Also, planting equal pounds of Rhizo-Kote XL alfalfa seed result in significantly greater emergence and survival, an indication that more of the seed planted with Rhizo-Kote XL became plants as compared to uncoated pre-inoculated seed.
Auburn University conducted some research on how to inoculate arrowleaf clover. Arrowleaf takes a specific rhizobia and there is very little in soils where arrowleaf hasn’t been grown before. In one treatment the seed received inoculum and a coating to seal in the inoculum. On the second treatment the inoculum was put on the seed, without a coating. The results are shown below.
Table 4. Arrowleaf Clover Inoculation Treatments.
| Seed Treatments |
Dry Forage Per Acre |
|
|
Tallassee, AL |
Prattville, AL |
|
|
March 11 |
April 5 |
|
| Coated seed |
870 lbs. |
1,520 lbs. |
| Uncoated seed |
290 lbs. |
500 lbs. |
| Increase due to coating |
580 lbs. |
1,020 lbs. |
When coated and uncoated arrowleaf clover seed were planted in the fall, by March 11, the coated seed had produced 580 lb. more dry forage at Tallassee and by April 5, 1,020 lb. more forage at Prattville than the uncoated seed.
Industry experience has shown that up to ten times the number of rhizobia can be loaded onto a seed using the Rhizo-Kote XL coating compared to uncoated seed.
Why Coat Legume Seed?
To put rhizobia (inoculum) on the seed whereby the plants would have large amounts of inoculum available for quick nodulation.
To provide a mico-environment for quick growth of the rhizobia by putting calcium carbonate and other growth encouraging materials in the coating.
To increase yields by assisting with quick nodulation and providing specific strains of Rhizobium for maximum efficiency.
To protect inoculum from damage by fertilizer salts for short periods of time in order to mix seed and fertilizer and broadcast them together.
To encourage easier seed flow. Because the seed flow through seeders easier, seeders should be calibrated using coated seed.
Apron, a fungicide, can be included in the coating process and will assist in seedling disease control.
To help stretch the supply of limited amounts of seed, particularly new varieties. More farmers are able to plant more acres of newer, more productive varieties.
Why Coat Grass Seed?
To put nutrients around the seed for quick seedling growth. This is a very precise method and if it isn’t done correctly, the germination of the grass seed can be lowered significantly.
For bermudagrass, the extra weight of the coating helps to insure easier and more uniform seeding of this very small seed. Coated ryegrass and other grasses broadcast with a cyclone type seeder also give a better seeding pattern. Coated seed penetrate bermuda and other stubble for improved seed-soil contact for better and quicker germination and growth.
Apron fungicide can be added to the coating which helps control seedling disease.
Summary
It is believed the use of coated seed will continue to increase in the area of forage crops as well as field and vegetable crops and turf. Many of you have seen the displays of the colorful turf grass seed in the retail stores. This is a way coated seed is used to attract customers. The coating of alfalfa seed will probably remain the volume leader for the immediate future, but other crops may get into the race. With the new technology of film coating and with a generation of new highly active and extremely low rate pesticides, the seed coating industry will take the lead in servicing the people and protecting the environment.
Acknowledgements
A special “THANK YOU” to Forage Specialists, Drs. Don Ball, AL; Jimmy Henning, KY and Gary Bates, TN and to county agents, Randall Armstrong and the late Watt Carter, AL; Keenan Turner, Dan Grigson and David Herbst, KY; Bob Sliger, Bill Reed, Tim Woods, Billy Adcock, Ed Burns, Jon Baker, Kevin Rose, Steve Hale, Milton Orr, Paul Hart and Ron Blair, TN, for helping to conduct these Strip Tests. Also, to the farmers who were excellent cooperators: Eugene Glenn and Lawrence Collier, AL; Dale Henderson, Jeff Reed and A. B. Corbin, Jr., KY and Sammy Cook, Fred Warmbrod, Bill Barr, Marty Builderback, Joel McDaniel, Neil Manley, Steve Sacchinelli and Lanny Love, TN. From Celpril: Kelly Rooney, Brad Bennett, Jeff Hensley and John Walsh. It was truely a privilege to have worked with such an outstanding group of men in conducting the alfalfa strip tests.
REFERENCES
Cosgrove, Dennis and Dan Undersander. 1992. When to plow down alfalfa – new stand density recommendations.
Forage Producers Use Symposium, Wisconsin Forage Council 16th Proceedings: 84-86.
Rooney, Kelly, Joel Canestrino and John Walsh. 1999. Establishment and Yield of Coated Alfalfa Seed in Commercial Fields. American Forage and Grassland Council Abstracts Vol. 8:69-70.
Wade, R. H., C. S. Hoveland and A. E. Hiltbold. 1972. Inoculum Rate and Pelleting of Arrowleaf Clover Seed. Agron. J. 64:481-483.