Ipomoea batatas (Convolvulaceae or morningglory family)
Production
Soil preparation
- Total nutrient uptake is 140 lbs. of N, 20 lbs. of P and 200 lbs. of K.
- Apply compost and other amendments based on the results of a soil test.
- Spread lime as needed to increase both the pH and Ca levels. Dolomite lime will also increase Mg levels. 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.
- 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.
- Sweet potatoes don’t do well when nitrogen is applied before planting. Instead, using a slow-release compost like feather meal is advisable.
- Incorporate compost and plant sweet potatoes on high raised beds covered with plastic mulch, or on ridges.
Common recommended fertilizer rates1
| Nitrogen | Phosphorus | Potassium | pH |
| 75 | 0-300 | 0-350 | 5.0-6.8 |
| 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
- New York variety trial
- New Hampshire variety trial
- Sweet potato varieties released by North Carolina State University
- Plants are bought as bare-root slips.
- Covington and Bauereguard are popular varieties. Select Murasaki when you want a purple sweet potato with white flesh.
Transplanter
| Rows | In-row spacing | Planting depth (inches) | Notes |
| 2 rows, 30–36 inches apart | 12 inches | Plant deep for the highest yield. All roots should be firmly underground without burying the growing point. | Plant the slips immediately after receiving them. Don’t store them in a cooler or set them in water. Irrigate after planting. The distance between rows is based on wheel track spacing. |
Transplanting tips
- In-row spacing should be a maximum of 12 inches because sweet potatoes do better with closer spacing.
Cultivation procedures (without plasticulture)
- Use a tine weeder for the first cultivation, but make sure plants are firmly rooted first.
- For all other cultivations, continue to hill up the sweet potatoes without burying the plants.
- Make several passes and remove any remaining weeds by hand.
Cultivation procedures (with plasticulture)
- Cultivate twice in between plastic with a rolling cultivator or Spyder to control weeds.
- Don’t cover the wheel tracks with rye straw because such a cover can attract field mice and voles that will damage the crop.
- Instead, vines will quickly cover the wheel tracks to provide weed control.
Deer, disease and insect protection
- Check the soil for wireworms, as a high population can make sweet potatoes unmarketable. 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.
- Deer can do extensive damage to sweet potatoes, as it’s one of their favorite crops. To prevent deer damage, build a temporary fence using 4-foot fiberglass posts and attach 1 clearly visible wire like IntelliTape at about knee height. Build a second fence inside the first fence, but attach 2 wires or twine whereby the top line is about 7-feet tall. Deer don’t have very good depth perception and won’t attempt to jump this fence without checking out the first fence, so electrifying the second fence is often not needed. Bait the outside deer fence with peanut butter and electrify it. Make sure you build the fences, bait and electrify on the same day. The surprise effect is what matters most with this particular deer control.
- Mow foliage and harvest tubers before the soil temperature dips below 60˚.
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.
Double cropping and/or cover cropping
- A cover crop of rye and hairy vetch usually follows sweet potatoes.
Additional resources
- North Carolina Organic Sweet Potato Production
- Cornell University: Considerations when planting sweet potatoes
Harvest
| Yield | An average of 1.2 lbs. of marketable, cured sweet potatoes per row foot, with climate having a great influence on yield. Sweet potatoes continue to put on weight until harvest, and size is controlled in southern states by timely harvesting. In the Northeast, reaching optimum yield requires a full growing season. |
| Standards | Harvesting1 200–250 lbs. per person, per hour |
| Tools and supplies needed | Buckets, bulk bins, and either a tractor with a potato digger or a tractor with a bedlifter and another with a forklift. Use a hand fork when harvesting by hand. |
| 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
- Harvest sweet potatoes before the soil temperature goes below 55°.
- Grade 1 sweet potatoes for wholesale are 3–9 inches long, and the tubers have a diameter of 1 ¾–3 inches. Individual tubers cannot weigh more than 1.125 lbs.
- In North Carolina, the correct harvest date is when most of the tubers have reached their optimum dimension for a high pack-out. In the Northeast, the time when tubers reach their optimum size greatly depends on the season and location.
- All harvested tubers are free from defects.
Harvest procedures
- Before using a bedlifter or root digger, you may have to mow the vines or cut them by hand and set them aside.
- For bulk harvest: Place about 30 buckets on the harvester. One person drives the tractor while 3–4 people sort out the good potatoes on the machine and place them on the outside chains. One or 2 people change the buckets on the back of the harvester. Bring the full buckets to the harvest lane. One person drives the tractor with a bulk bin down the harvest lane and carefully dumps the potatoes into the bin.
- Sweet potatoes are easily bruised, so you need to handle them gently.
- You need to cure sweet potatoes in a greenhouse or a curing chamber for 10 days at 85°. Cover the greenhouse with 80% shade cloth. Cover up the bins with tarps to protect against sunscald, but allow them to breathe (don’t use plastic).
Washing procedures
- After curing, you can easily remove any soil particles left on the sweet potatoes by hand. Some soil particles left on a sweet potato don’t harm it, but you should remove most dirt before long-term storage. If you need to wash sweet potatoes it’s best to do this after curing and right before delivery, because the washing procedure can shorten their life and introduce mold.
Additional resources
- Sweet Potatoes Visual
- Postharvest Factsheet Sweet Potatoes
- Production Guide for Storage of Organic Fruits and Vegetables
Packing and storage summary for sweet potatoes
| Packing in the field | Remove large chunks of dirt |
| Packing for delivery | Sort by size and pack into 40 lb. sweet potato boxes. For a CSA delivery, pack potatoes in a 2–3 lb. paper bag, and pack these in boxes. See the International Federation for Produce Standards for the correct PLU code. Add the prefix 9 for organic crops. |
| Storage | 55° and 80% humidity. Sweet potatoes are moderately sensitive to ethylene exposure, which affects flavor and color. Allow for good air exchange and don’t store them with crops that release ethylene. |
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.