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Seed Cutting and Planting Rates | |
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| | Seed cutting | Determining cut-seed size | Planting rates
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Return to the Guide to Commercial Potato Production on the Canadian Prairies
Seed Cutting
Most European growers plant small, whole seed tubers. An increasing number of Canadian growers are planting whole seed, but the most common practice is to cut whole seed tubers into smaller seed pieces.
The object of cutting is to produce uniform seed pieces with an average weight between 1.75 and 2.25 oz (50 and 65 g). Growers should consult with their provincial potato specialist or processor field staff for seed size recommendations. Some varieties (Shepody and Yukon Gold) have poor eye distribution and larger seed pieces ranging from 2.25 to 2.50 oz (64 to 71 g) are recommended.
The majority of mother tubers in an uncut seed lot should be 8 oz (225 g) or less, with few tubers greater than 10 oz (225 to 300 g). Growers should maximize the number of seed pieces with single cuts, and minimize the number of tubers with two and three cut surfaces. This can only be accomplished if the mother seed lot does not contain many tubers over 8 oz. Variation in seed piece size results in variability of size, shape and yield of tubers from plant to plant.
Seed pieces weighing less than 1.5 oz (35 g) are referred to as seed chips. The chip eliminator rollers on the seedcutter should remove the seed chips because they result in unproductive plants. Improper chip eliminator roller adjustment or overloading the cutter are the main causes of excessive numbers or chips in a cut seed lot.
To reduce seed piece infections, cutter knives must be kept sharp. Sharp blades result in smooth cut surfaces that suberize (heal) quickly. Dull blades cause ragged cut surfaces that are easily infected with decay organisms. Cutters should be disinfected at least once a day or between every seed lot. Pay special attention when disinfecting the rollers as they tend to hold pathogen-laden debris. If seed is handled or cut at a temperature of 45°F (7°C) or less, the incidence of shattering bruising may increase and cause seed decay.
Seed piece fungicide treatments should be applied to all seed lots immediately after cutting. Growers must assess field location and seed source histories to determine which fungicide seed treatment to apply. Seed treatments effective against late blight are recommended if the seed originated from an area where late blight was reported. Other seed-piece treatments that control Rhizoctonia sp. and silver scurf are recommended when seed or field location indicates a risk for disease inoculum.
Determining Cut-Seed Size
Producers should manage seed cutting so the average seed piece is 2 oz (60 g) and the majority of pieces are between 1.5 and 3 oz (35-85 g). Specialty market needs may demand different seed sizes and growers should verify these needs with packer or processing field staff.
Cutter performance is determined by regularly calculating the average cut seed size and seed size distribution. At the very least, these calculations should be performed each time a new seed lot is cut. Mother tuber size, which varies with each seed lot, affects the performance of the cutter. During cutting, samples of seed pieces should be collected and individually weighed. The average size is calculated by dividing the weight by the number of seed pieces.
For example, a 12.5 lb (5.4 kg) sample with 97 pieces has an average weight of just over 2 oz (60 g). The average seed size is not a good measurement of seed cutter adjustment. The average seed size may be ideal (2 oz (60 g)), but a majority of the cut seed sizes might occur outside the ideal seed size range of 1.5 to 3 oz (35-85 g). Seed size distribution is the best measurement of the cutter performance. This is determined by individually weighing and arranging the seed pieces into size groups such as less than 1.5 oz (35 g), 1.5 to 3 oz (35-85 g), and greater than 3 oz (80 g). Pieces can be further separated according to the number of cut surfaces such as whole seed, one cut surface, two cut surfaces and three cut surfaces.
Cutter adjustment chart
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Seed cutter adjustment is complicated and novice growers should seek advice from the dealer, processor or provincial potato agronomist.
Planting Rates
Average seed weight, between-row spacing and in-row spacing affect the amount of seed required per acre or hectare. Between-row spacing varies from 34 to 38" (86-97 cm), with 36" (91 cm) being the most common in Alberta and Saskatchewan and 38" (97 cm) the most common in Manitoba. In-row spacing varies between production areas, variety and market. See section 3.3.2 In-row Seed Spacing to determine the appropriate in-row spacing.
 | | In-row spacing |
| | 6" (15 cm) | 8" (20 cm) | 10" (25 cm) | 12" (31 cm) | 14" (36 cm) | 16" (41 cm) | 18" (46 cm) |
Seed @ 36" (91 cm)
row spacing | lbs /ac | 3600 | 2700 | 2400 | 1800 | 1600 | 1400 | 1200 |
| kg/ha | 4035 | 3026 | 2690 | 2018 | 1793 | 1569 | 1345 |
Seed @ 36" (91 cm)
row spacing | lbs /ac | 3400 | 2600 | 2300 | 1700 | 1500 | 1300 | 1150 |
| kg/ha | 3811 | 2914 | 2578 | 1905 | 1681 | 1457 | 1289 |
Written by L. Delanoy, C. Schaupmeyer, D. Ziprick, D. Kirkham |
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For more information about the content of this document, contact Shelley Barkley.
This information published to the web on January 12, 2005.
Last Reviewed/Revised on September 23, 2008.
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