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Many of the practices used in seed production are similar to those used in commercial production. Only those practices that are specific to seed production are discussed in this section. The reader should read the commercial production section of this manual to obtain a more complete understanding of potato production and storage practices.
Seed Selection and Handling
A potato crop is only as good as the seed. When purchasing seed, ensure the supplier has a reputation of delivering a quality product. Also, check that the growing area has a history of producing quality seed. A visit to prospective seed suppliers both during the growing season and once the crop is in storage will assist to ensure quality. Before buying any seed for re-certification, the grower should be satisfied that the seed is going to have a good chance of passing the certification inspections. It is generally fruitless to plant a seed lot having even a low incidence of disease with the expectation that the diseased plants can be removed through roguing. Check the results of field and storage inspections and insist on Post Harvest test results before agreeing to purchase seed. See the section on Post Harvest Testing for more information. When negotiating purchase of a seed lot, determine the method of delivery, date of delivery, desired tuber size distribution, tuber temperature and degree of sprout development.
Inspect the seed immediately (and frequently) during delivery to ensure that it meets the agreed upon quality stipulations. The buyer should contact both the seed potato grower and CFIA within two working days after receiving the seed potatoes, if not satisfied with the quality. If a re-inspection is requested it will be carried out by a CFIA inspector within five working days after receipt of the complaint. The buyer should have seed tags and some unopened sacks (for bagged lots) or the bulk-movement certificate (for bulk lots) on hand, so that the proper information can be conveyed to the inspector when lodging a complaint.
All machinery, transport and storage surfaces that the seed will contact should be cleaned and disinfected prior to receiving new seed. Sanitation consists of cleaning and disinfecting all equipment, storage, tools and pallet boxes that contact the seed potatoes. Since most disinfectants are inactivated by soil and plant debris, it is essential that this material be removed by thoroughly cleaning the equipment and storage with a pressure washer or steam cleaner before the disinfectant is applied. The seed storage and all equipment coming in contact with the seed lot should be disinfected with a quaternary ammonium compound such as Ag-Services Incorporated General Storage Disinfectant, Bardak 2210 Disinfectant Sanitizer, or DMR-23 Disinfectant. Surfaces must remain wet for at least 10 minutes for the disinfectant to destroy disease organisms.
Restrict contact between incoming seed lots and any potatoes left over from the previous year. Cull potatoes are a particularly important potential source of disease. Avoid sharing equipment between farms; sharing seed cutting equipment is particularly risky.
Whole versus cut seed (See the section Whole Versus Cut Seed)
Whole seed has many advantages over cut seed, particularly in the production of seed potatoes:
- The wounds produced by cutting seed presents entry points for many disease-causing organisms
- Seed cutting equipment contaminated with a disease pathogen spreads disease both within and between seed lots
- Where the seed regulations require tuber unit planting the planting of whole seed is an acceptable alternative
- Whole seed tends to produce large numbers of relatively small tubers, which is ideal for seed production
- Whole seed generally produces a more uniform stand both in emergence percentage and in growth characteristics, which makes more efficient use of the production inputs (irrigation water, fertilizers
- and pesticides)
- Whole seed eliminates the equipment and labor cost of cutting.
Seed cutting (See the sections Seed Cutting and Determining Cut-Seed Size)
Planting (See the section on Planting Management)
Timely planting is as important in seed production as in table or processing production. Plant early and plan on an early vine kill and harvest. This will reduce the risk of introduction and spread of viral diseases by late season winged aphid. Plant the highest generation seed Check the results of field and storage inspections and insist on Post Harvest test results before agreeing to purchase seed lots first to minimize risk of disease. Clean all equipment between seed lots. Cup type planters are less likely to spread disease within a seed lot than pick-type
planters.
Seed spacing (See the section In-Row Seed Spacing)
In-row spacing is the main factor controlling tuber size. Optimum seed spacing is based on varietal characteristics and climactic conditions. Closer in-row spacing is used in seed production to maximize yield of the desirable, smaller tuber sizes. In-row spacing of 6-12" (15-30 cm) are recommended for seed production, depending on variety, irrigated or rain-fed production, area in which the potatoes are grown and other climactic conditions
Fertility (See the section Fertility and Fertilizers)
Fertility requirements for seed are generally comparable to other types of production. Highly vigorous, early-generation seed may require less fertilizer for optimum yields, particularly if the crop is grown under rain-fed conditions or is going to be top-killed early.
Weed control (See the section Weed Management)
Uncontrolled weed growth in seed potato fields will:
- Interfere with proper inspection and roguing
- Restrict air flow through the canopy which increases the potential for disease development
- Provide alternate hosts for diseases and insects capable of spreading disease.
- Rob the crop of fertility and moisture
- Interfere with a timely and gentle harvest
Effective weed control in seed fields can be obtained through timely tillage and the application of approved herbicides. Note that some herbicides registered for use in table and processing potatoes are not recommended in seed crops. Caution should be exercised when applying herbicides to adjacent crops. Drift of certain herbicides can be translocated to the daughter tubers. The affected tubers lack vigor and produce plants displaying symptoms of herbicide injury. Herbicide residues from previous crops can also be taken up by the seed crop producing similar results.
Written by Dennis Lidgett |
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