The purpose of this study was to develop a procedure to determine seed moisture content from intact pelleted seeds. Samples of `Sentinel' onion and `Salinas' lettuce were pelleted by the following companies; Asgrow, Germains (Seed Systems), Harris Moran, Incotec, Peto and Seed Dynamics. Physical characteristics of the various pellets were quantified including weight, volume and density. Measurements were made on intact pellets and densities ranged from 0.84 to 1.67 g/cc. Seed drying curves were obtained on the different pellets under controlled environmental conditions. Pellets were first equilibrated at 85% RH, and then dried at 25C and 18% RH. In general drying rates were similar among pellet types within crops. With regards to seed moisture content determination, neither the electronic moisture meter, based on measuring capacitance, nor oven methods were able to accurately measure seed moisture from intact pellets. Measurement of the head space RH from pre-equilibrated intact pellets (water activity) resulted in an accurate method to assess seed water status for all samples. The actual seed moisture content could be determined by using the moisture isotherms for each seed lot at a given temperature.
A. G. Taylor, D. H. Paine, and D. F. Grabe
M. Sachs, D. J. Cantliffe, and T. A. Nell
Germination rate of sand-coated pepper (Capsicum annum L.) seed (sand grain size < 75μm for an inner coat and 75–105 μm for an outer coat layer) was faster than clay-coated seed but was slower than raw seed. Part of the germination reduction in sand-coated seeds was caused by the water-soluble Gelvatol binder used. High oxygen (O2) levels promoted the germination of sand-coated seed to a rate comparable to that of raw seed. This suggests that even with a porous sand-coating material, O2 may be limiting for the germinating seed. When inorganic O2-releasing compounds (BaO2 or NaBO3) were incorporated into the sand material, the germination of pepper seed was further inhibited.
M. Sachs, D. J. Cantliffe, and T. A. Nell
Seed germination of sweet pepper (Capsicum annuum L.) is inhibited after the seed is coated. The inhibitory effect of pellet-coating of ‘Early Calwonder’ pepper seed was caused by the physical properties of the coating materials. Clay coating limited part of the oxygen (O2) from reaching the germinating seed and provided a mechanical barrier to protrusion of the radicle. Clay-coated pepper seed germinated satisfactorily on filter paper in a high O2 environment or with minimum moisture on agar. Pellet coating formulations which would provide more O2 to the imbibing seed would assure comparable germination of raw and coated sweet pepper seed.
Brian A. Kahn, Niels O. Maness, Donna R. Chrz, and Lynda K. Carrier
study the feasibility of establishing basil in the field by direct seeding. We examined factors including use of raw seed or pelleted seed, seeding depth, seeding rate, and comparison with transplanting. Materials and Methods Studies were conducted at
Ahmet Korkmaz and Wallace Pill
Achievement of head size uniformity at final harvest reduces loss and increases profitability for the hydroponic lettuce grower. Shoot fresh weight of `Cortina' lettuce (Lactuca sativa L.) at 7 or 21 days after planting (DAP) was inversely proportional to the number of days required for seedling emergence, and was greater for raw than for pelleted seeds. Head fresh weight at final harvest (61 DAP) was directly proportional to seedling length at 21 DAP, but raw and pelleted seeds produced equal head weights. Thus, initial seed (seedling) vigor differences were maintained to final harvest. Osmotic seed priming (–1.5 MPa KH2PO4, 20 h, dark) led to increased germination rate at 15, 25, and 35C; had no effect on germination synchrony; and increased germination percentage only at 35C. Covering raw or pelleted seeds sown in depressions of the phenolic foam trays with fine (No. 5) vermiculite compared to leaving the seeds uncovered, and soaking the trays in hydroponic solution rather than water, increased seedling shoot fresh weights. Seeds sown on their first day of germination or primed seeds gave greater seedling shoot fresh weights than pelleted seeds. However, the more uniform seedling shoot fresh weights from germinated seeds than from primed seeds was associated with more rapid and synchronous seedling emergence.
The use and improvement of pelleted seed technology has greatly expanded in the last 15 years. Vegetable and flower seeds are pelleted to improve the singulation and planting placement in the field and greenhouse. Improved planting placement increases final-stand establishment, crop uniformity, and decreases seed and production costs. The commercial history of pelleted seed in the U.S. started after WWII with the development of the clay pellet by Filtrol Inc. Seed tablets and seed tape technologies were also developed but faded from the industry with the advent of better pelleted products. Current technology consists of a “splitting” seed pellet that allows for improved oxygenation. Improved technology also allows for pellet weights that can be tailored to meet the planting requirements of different species and planting systems.
Aleta L Meyr
Ideally, a vigor test should provide a reasonably accurate forecast of greenhouse or field quality under a wide range of conditions. A vigor test could provide useful data any time during the different stages of development: Before harvest, after harvest, through handling, natural maturation, and decline. Vigor information on a lot of seed is desirable before distribution and conditioning, after conditioning and before planting. Can one vigor test meet all these needs? The most practical seed vigor test should include several different tests which could be combined and indexed. At the Ransom Seed Laboratory we have developed a series of vigor tests which we combine for a vigor index. We perform four tests: 1. Seed weight or seedling length in pelleted seed. 2. Standard % germination as set forth by A.O.S.A. 3. Stand uniformity index at an early count which includes a photograph of one replicate of 25 seedlings. 4. Stress test: % germination at an alternative temperature. (varies from cold tests to heat tests). No single test is sufficient to communicate seed vigor. If several tests are used to form a vigor index, the actual data for each test should be communicated along with the vigor index, so the user can evaluate the data and utilize the vigor index to its fullest potential.
Alan G. Taylor
High seed quality is required to obtain optimal plant stands and to achieve maximum yield potential. Onion seeds are commonly coated and treated with an insecticide and fungicide to control early season insects and diseases. The seed treatments may cause phytotoxicity in standard germination tests, and thus reduce the percent germination of a seed lot. The objective of this study was to examine the effect of seed quality on seed storage, stand establishment and yield. Two seed lots of two long-day onion varieties were pelleted and treated with the seed treatments Trigard and Pro-Gro. Standard germination and saturated salt aging tests were performed on each seed lot, indicating a high and lower quality seed lot for each variety. Aging was conducted by equilibrating pelleted seeds at 35% relative humidity and aging at 25 °C for up to 12 months. Aging decreased germination with time, especially for the lower quality lots. Field studies were conducted in two locations in upstate New York. The plant stand was greater in the high compared to the lower quality lots in both varieties at both locations. Yield was reduced in the lower quality than high quality lot; however, the response differed by variety and location. Overall, the initial seed quality had an impact on seed storagability, stand establishment and yield.
Charles W. Marr
Seedlings are established in small growing containers to reduce cost of greenhouse space, while improving crop uniformity. These seedlings often are referred to as plugs. Vacuum seeders are used by larger growers to seed many flats per season (Bakos, 1983); however, individual growers, producing plants for their own use, may not be able to justify expensive seeding equipment. Several moderately priced vacuum seeders are available (Bartok, 1988). They consist of a metal tray with small drilled holes to hold the seed in place when a vacuum is applied to the tray from an external source. However, several problems with them exist. Seeds must be free of extraneous materials that might clog the small holes. A slight jarring of the plate, especially when the plate is turned upside down over the seed flat, may cause seeds to dislodge, resulting in unplanted cells in each flat. Also, different sizes of seeds and flats require completely different seeding plates and plate holders. A small grower may choose to seed flats by hand by placing seeds individually in each cell. This is feasible only for large-sized seeds or with pelleted seed. A simple, inexpensive, non-vacuum alternative design is presented and evaluated.
Ahmet Korkmaz, Wallace G. Pill, and Bruce B. Cobb
The effect of seed germination rate, or of seedling emergence rate, was studied in relation to subsequent plant growth of `Cortina' lettuce (Lactuca sativa L.). Seedling growth response to selection by time of germination was assessed by imbibing seeds at 5 °C to increase the time range for germination. Germinated seeds were removed daily and transferred to “slants” (germination paper held at 20° from vertical) at 15 °C. Five days after each transfer, root and hypocotyl lengths were measured. As days required for germination increased, root lengths decreased and hypocotyl lengths increased, resulting in no change in total seedling length. The relation between rate of seedling emergence from raw or pelleted seeds of the same lot and shoot fresh weight was examined using commercially practiced hydroponic techniques. Shoot fresh weight at 10 and 21 days after planting was related inversely and linearly to the day of emergence for both seed treatments. In the same study, the coefficient of variation of shoot fresh weight was positively related to time of seedling emergence only at 10 days. Germinated seeds were selected after 1 and 2 days of imbibition; subsequent seedling emergence rate and shoot fresh weight at 25 days were recorded. First-day germinated seeds had faster and more synchronous emergence, and produced heavier and more uniform shoots. Discarding slow-to-germinate seeds should enhance seedling emergence and growth.