Solanum tuberosum (Solanaceae or nightshade family)
Production
Soil preparation
- Total nutrient uptake is 180 lbs. of N, 26 lbs. of P and 225 lbs. of K.
- Apply compost and other amendments based on the results of a soil test.
- Spread gypsum when calcium levels are low but pH is correct.
- A fertilizer company can add OMRI-listed potassium sulfate to compost if it doesn’t have enough K to meet the crop’s needs. If this isn’t possible, spread the correct amount of fertilizer and incorporate it before planting. Alternatively, you can side-dress it during cultivation. Divide the recommended rate of the soil test in half if side-dressing.
- Most vegetable crops remove little P, but at times your soil test result will call for additional P. Unfortunately, there aren’t short-term options for an organic grower to increase the available P levels in the soil. Through the use of animal-based fertilizers, P will build up to a level in the soil that is sufficient for all vegetable crops.
- Incorporate compost and create a fluffy seedbed, as potatoes need much air to prosper.
Common recommended fertilizer rates1
| Nitrogen | Phosphorus | Potassium | pH |
| 150 | 0-240 | 50-350 | 5.0-6.5 |
| 1Rates are for New York and are from Cornell University’s Nutrient Guidelines for Commercial Vegetable Production (2019). Check the Cornell website for updated guidelines, or consult with local experts for recommended rates outside New York. | |||
Varieties
- North Dakota variety trial
- Idaho, Washington State and Oregon variety trial
- Michigan variety trial
- Yellow: Keuka Gold, Natasha, Satina, Nicola
- White: Kennebec, Green Mountain, Lehigh
- Red: Red Maria, Adirondack Red, Chieftain
- Russet: Amey Russet, Gold Rush
- Purple: Adirondack Blue, Magic Molly
- Fingerling: Yellow Finn
Planting in the field with a potato planter
| Rows | In-row spacing | Planting depth (inches) | Notes |
| 2 | See notes. | As deep as the planter allows the seed potatoes to be dropped in the furrow, but no deeper than 2–3 inches. | For regular potatoes, use an in-row spacing of 7–9 inches. For russets, use 12 inches. 100 lbs. of seed potatoes can cover approximately 600 row feet. Any potatoes larger than B size need to be cut into smaller pieces. Make sure each piece has at least 1 eye. |
Cultivation procedures
- Use a tine weeder or rolling cultivator when weeds are in the white thread stage. Make sure tubers are well rooted at this point.
- Use a ridger or large discs to hill the potatoes, and drive carefully to avoid burying them.
- This will take several passes and as the potato plants grow, you can become increasingly more aggressive in the amount of soil you mount up. The objective is to cover all emerging weeds after each pass.
- Potatoes are fast-growing plants, and the shade from their leaves will control weeds until they’re ready for harvest.
- Weed control becomes very challenging when leafhopper control isn’t adequate and potato leaves are damaged to the point that they’re defoliated before developing a hard skin. Exposed soil will allow new weed seeds to germinate. Mechanically harvesting potatoes before they have developed a skin will create many post-harvest issues, so you’re left with little choice but to leave the potatoes in the ground. There is no good way of controlling weeds at this stage, as additional ridging or hilling will either expose the tubers to sunlight or damage them.
Frost, disease, and insect protection
- Plant potatoes when soil temperature is above 50°.
- Prevent potato scab (Streptomyces scabies) by selecting resistant varieties, selecting ground with a low pH (lower than 5.2), broad crop rotation and timely irrigation.
- You can prevent cutworms by spraying the soil with the beneficial nematode Steinernema carpocapsae. Once the pest is in the crop, control the population by spraying the crop with Bacillus thuringiensis kurstaki, or spread a baited product containing spinosyn, like Seduce, around the plants.
- Check the soil for wireworms, as a high population can cause yield decline. To avoid wireworm damage, rotate with crops like onions, lettuce or alfalfa, or include buckwheat as a cover crop the previous year. Some results have been obtained using beneficial entomopathogenic nematodes. Promising results have also been obtained applying Beauveria bassiana.
- For Colorado potato beetles move potatoes as far away from last year’s plot as possible. Use Bacillus thurigiensis subsp. tenebrionis, available as a product in Novodor™, for killing beetles in the larva stage. Use Entrust only to kill adult potato beetles. Potatoes can host a great variety of beneficials, so avoid spraying the whole field. Use a backpack sprayer for spot spraying.
- Potato leafhoppers can be a big problem for organic potato growers. For leafhopper control, use Beauveria bassiana (as in the product Mycotrol ESO) at nymph stage. You’ll see results after a week of applying. Use it when pest pressure is still low. When pressure is high, use a pyrethrum-based product (as in PyGanic EC 5.0 II). Make sure water is neutral, as either a low or high pH will make PyGanic EC 5.0 II ineffective. Pyrethrum breaks down quickly when exposed to UV light (it has a half-life of 12 hours) and is considered among the shortest-acting insecticides. It’s also toxic to bees and other pollinators. For both reasons, apply a pyrethrum-based product in the evening.
- Late blight can only be controlled preventively. Once the disease is visible, you’re too late. Follow local Extension updates on whether late blight has been observed in your region, and start applying an OMRI-listed product. Here are some options: a weekly spray of a biosurfactant based on Pseudomonas aeruginosa, as in the product Zonix. OMRI-listed coppers combined with a spreader sticker/adjuvant can be quite effective. Some growers have success using mineral oil, as in JMS Stylet-Oil, in lieu of a spreader sticker. Don’t use both adjuvants and mineral oil, as this will cause crop damage. Weekly applications of a giant knotweed extract (Reynoutria sachalinensis), as in the product Regalia, helps the plant’s immune system. Note that because late blight can become airborne, it will affect both the foliage and the tuber, but waiting to harvest until all foliage has decomposed may avoid crop loss, because phytophthora can only survive on living tissue.
Other cultural practices
- Irrigate frequently for optimum yield and plant health. Frequency depends on soil type, evaporation, precipitation and the particular needs of the crop. When potatoes flower, ensure they have abundant moisture because this is a critical stage in their development.
Double cropping and/or cover cropping
- Potatoes can be followed by rye and vetch.
Additional resources
Harvest
| Yield | An average yield of 1.3 lbs. of potatoes per row foot is common on the East Coast. Expect fingerlings to yield significantly less. |
| Standards | Harvesting1 300–400 lbs. per person, per hour (10–16 buckets) when using a mechanical harvester. Don’t expect to harvest more than 50 lbs. per hour when forking potatoes out by hand. |
| Washing and shorting 500 lbs. per person, per hour | |
| Tools and supplies needed | ⅝-bushel buckets, digging forks for manual harvest or a tractor with a potato digger, a tractor with a forklift, and 20-bushel bulk bins. |
| 1Harvest rates don't include the time required to transport crops from the field to a wash and pack shed or storage facility. | |
Ready-to-harvest and quality indicators
- Potatoes are firm, free from defects and have an intact skin.
- Wait until the vines have died down before harvesting potatoes. This improves the quality of the potatoes, as the tubers start removing themselves from the stolons and the skin begins to harden up after the vines die. Also, if late blight is a problem, you might be able to protect the tubers from infection. Conventionally this is also done to control tuber size because the tubers stop growing after the vines die down. This is exactly the reason why organic growers in the Northeast have relatively small yields. Many organic potatoes don’t require vine killing, as the leafhoppers tend to do this. Even a good spraying program doesn’t control the whole leafhopper population. Inspect the crop for pathogens like Rhizoctonia and late blight before the vines die down, as they will continue to cause problems in storage. If vine kill is needed, mow 10 days to 2 weeks before harvest.
- Periods of heavy rain after vine kill can result in a pathogen infection of the tubers, so growers may have to dig earlier than expected to avoid heavy rainfall.
- Before digging, check that potatoes have developed a good skin set, which means that the skin won’t easily rub off during handling. Dig up a few plants to determine if the tubers are ready to handle your harvest equipment.
- For early harvest (July–August): Potatoes have sized up to make a harvest worthwhile. Treat these new potatoes very gently, as they have not developed firm skin yet. Many mechanical harvesters aren’t designed for early potatoes. If you don’t have a bedlifter, and hand forking is not an option, you can attempt to use a mechanical harvester by digging deep and allowing soil to remain on the chains. Preventing the potatoes from getting in touch with the metal chains should protect the skin. Also, your crew should handle the potatoes with care when picking them up from the ground. Bring the new potatoes into a pack shed and allow some skin to form by forcing air through the stack using a plenum. Once the potatoes are dry, you can attempt to wash them gently with a brusher washer.
- Harvest for storage (mid-September into October): If at this point the vines have died back, the potatoes have formed a firm skin that doesn’t get easily damaged by the mechanical harvester. Allow for daytime air temperatures to drop to around 60° for ideal harvest circumstances. When the tubers’ core temperature is between 60–65°, they are less susceptible to bruising.
Harvest procedures
- If harvesting for new potatoes, dig them with a bed lifter or fork. Bring them into a barn and dry them with a high-speed fan until tubers are dry and skin does not peel off easily.
- Use a chain-type harvester for fall harvest. If picking up potatoes by hand, instruct the crew on how to select (grade) in the field.
- After picking up potatoes in buckets, transfer them into 20-bushel bulk bins. Have a tractor with forks drive slowly along the harvested bed so the crew doesn’t have to lug the buckets to the headland. If harvesting multiple beds, leave the buckets where you emptied them. This prevents unnecessary trips in retrieving buckets.
- If the harvester has a conveyor that places the potatoes in a bin, set up a conveyor in the barn to sort culls before they go into long-term storage.
- Curing potatoes for long-term storage is done at 59°F and 95% relative humidity for 1–2 weeks. Prevent condensation and allow for fresh air intake.
Washing procedures
- Wash hands and sanitize equipment before cleaning potatoes.
- It’s best to avoid washing or brushing new potatoes, as this removes their tender skin.
- If possible, only clean potatoes by dry brushing them.
- If this isn’t an option, you can wash them with a brusher washer.
- For drying, put 2 fans blowing at high speed towards the pallets with the washed potatoes.
- Potatoes are sorted for quality and size. Size A potatoes must be larger than 1 ⅞ inch.
- Distribute washed potatoes within a week.
Additional resources
- U.S. Standards for grades of Potatoes
- Potato Harvest and Storage Factsheet
- Production Guide for Storage of Organic Fruits and Vegetables
Packing and storage summary for potatoes
| Cleaning in the field | Select potatoes that are free from blemishes, bruises or rot. |
| Packing in the field | Load into 20-bushel bulk bins. |
| Packing for delivery | 50 lbs. in paper bags, sorted by size See the International Federation for Produce Standards for the correct PLU code. Add the prefix 9 for organic crops. |
| Storage | Potatoes need to be stored in absolute darkness to avoid greening of the skin. When curing potatoes, gradually bring the temperature down to the recommended level of 50°–60°. Extended storage is best at 39–41° and at 90–95% humidity for tablestock. At this temperature, the carbohydrates in potatoes convert to sugars over time, so potatoes stored in this way aren’t suitable for frying and are only for tablestock. |
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture through the Sustainable Agriculture Research and Education (SARE) program. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.