Best Soil for Sweet Potatoes: pH, Texture and Yield Data

The best soil for sweet potatoes is a deep, well-drained sandy loam or loamy sand with a pH of about 5.8 to 6.2, moderate organic matter and no standing water. That is the optimum range in the University of Maryland commercial sweet potato guide, which also says to avoid heavy ground and fields that hold water for more than 24 hours. Heavy clay can still grow a crop, but the roots tend to be smaller, rougher and more misshapen.

This guide ranks the main soil types for sweet potatoes, explains pH, drainage, salt and nutrients in plain terms, and shows how soil choice links to yield in the main US growing states. It also has a margin calculator so you can test whether a field pays at your own yield, price and costs.

Quick answer: what sweet potatoes need from soil

Sweet potatoes are a warm-season crop grown for a swollen storage root. The roots swell in the top layer of the bed, so the soil in that zone decides shape, skin finish and yield. Extension guides from Maryland, Tennessee, Texas and South Carolina cover six main points.

The rest of this page explains each point and how to fix a field that falls short.

Best soil for sweet potatoes, ranked by soil type

We ranked six common soil types by how well they meet the needs above. The ranking draws on the extension guides listed under “How we checked the numbers”. It is a guide to field choice, not a promise of yield. Local weather, variety, irrigation and pests all change the result.

1. Sandy loam

Best for: commercial fresh-market crops where shape and skin finish set the price.

Sandy loam drains fast but still holds some water and nutrients. Roots grow long and smooth. The Maryland guide names well-drained sandy to sandy loam soils as best for both bedding and production. Most of the North Carolina crop, the largest in the US, is grown on the sandy Coastal Plain.

Pros: easy digging, clean roots, low rot risk. Cons: needs irrigation in dry spells and loses potassium and nitrogen to leaching.

2. Fine sandy loam over a firmer subsoil

Best for: growers who want steady moisture without wet feet.

The Texas A&M AgriLife crop guide lists deep sandy loam, fine sandy loam or loamy fine sand underlain by a firm subsoil as the preferred soil, at pH 5.0 to 7.5. The firmer layer below holds water within reach of the roots, while the loose top lets them swell.

Pros: better water holding than pure sand. Cons: a hard pan too close to the surface can make roots short and blunt, so check depth with a probe.

3. Loamy sand

Best for: early digging and markets that pay for bright, clean skin.

Loamy sand warms early in spring and digs easily. Yields can be lower in dry years, because the soil holds little water. Steady watering of about 1 inch a week, the figure in the Clemson Home & Garden Information Center sweet potato fact sheet, keeps roots growing evenly and reduces cracking.

Pros: fast to warm, clean roots. Cons: drought stress, leaching, more fertilizer passes.

4. Silt loam

Best for: fields with good internal drainage and raised beds.

Silt loam holds more water and nutrients than sand. It can give good yields if it drains well. It crusts and packs when worked wet, so roots may be shorter and rounder. The University of Tennessee sweet potato guide says good drainage matters most, and heavier soils can be used if they are well aerated.

Pros: holds water and nutrients. Cons: compaction, crusting, slower drying after rain.

5. High organic matter or freshly broken sod

Best for: rarely a first choice; improve it with a cash crop first.

Some organic matter helps, but too much hurts. The Maryland guide warns against fields just broken out of hay or pasture, and says soils high in organic matter may promote scurf, a skin stain that lowers grade. Rich soil also frees a lot of nitrogen, which pushes vines at the expense of roots.

Pros: good structure and water holding. Cons: scurf, rank vines, soil insects from old sod.

6. Heavy clay

Best for: home gardens only, in raised beds with plenty of added compost.

Clay holds water and packs hard. The Clemson fact sheet says sweet potatoes grown in heavy clay may be smaller and misshapen. Clay also makes digging slow and causes more skinning and bruising at harvest. If clay is all you have, build ridges or raised beds and work in organic matter well before planting.

Pros: high nutrient holding. Cons: poor shape, rot in wet spells, hard harvest.

▶ Why soil organic matter matters for structure and water holding. · 7:33

How soil choice shows up in yield

Soil is only one of many yield factors, but the US state numbers show how much yield can vary. USDA reports yield in hundredweight (cwt) per acre; one cwt is 100 pounds. In the USDA NASS Vegetables 2025 Summary (February 2026), US sweet potato yield was 208.8 cwt per acre in 2025, up from 167.4 cwt in 2024. Production rose 31% to 32.5 million cwt, on 155,700 harvested acres.

Chart

US sweet potato yield per acre

cwt per harvested acre, United States

The yearly swing is large. Weather at planting and in late summer drives much of it, and good soil gives the crop a buffer. A well-drained sandy loam recovers faster from a heavy rain, and a soil with fair water holding rides out a short drought.

California has the highest yield per acre of the three main reported states. North Carolina grows the most acres. Mississippi yields are lower per acre. These numbers mix soil, irrigation, variety and market, so they are not a direct test of soil type.

Chart

Sweet potato yield by state, 2025

cwt per harvested acre, reported states and other-states group

Soil pH for sweet potatoes

Sweet potatoes like slightly acid soil. Both the Maryland and Tennessee guides give 5.8 to 6.2 as the ideal range. The Texas guide accepts a wider 5.0 to 7.5, and notes that a low pH of 5.0 to 5.5 helps reduce soil rot (also called pox). The Maryland guide goes lower still, 4.8 to 5.2, on fields where soil rot is a problem.

In practice, that means:

• Below 5.5: lime to raise pH by soil test, but do not overshoot, and skip lime on fields with a soil rot history, where the Maryland guide advises keeping pH at 4.8 to 5.2. Dolomitic lime also adds magnesium.
• 5.8 to 6.2: no change needed. Keep testing every two to three years.
• Above 6.5: do not lime. Watch for soil rot, and pick resistant varieties if the field has a history of it.

Timing matters. The Maryland guide says to apply lime several months before planting, so it has time to react. Lime spread at planting does little for that season.

How to test your soil

Take a soil test before you plant, and base lime and fertilizer on the result. The Clemson soil testing fact sheet explains the steps: take many cores from across the area, mix them in a clean plastic bucket, and keep areas that were limed or fertilized differently apart. A standard test reports pH plus phosphorus, potassium, calcium, magnesium, zinc, manganese, copper and boron.

For a farm field, sample each soil type or management zone on its own. A field with a sandy ridge and a heavier low spot needs two samples, because the two areas will need different lime and potassium. Ask the lab to test for nematodes at the same time if sweet potatoes, cotton or soybeans have been grown there.

Drainage, beds and soil temperature

Drainage is the one point every guide stresses. Waterlogged soil starves roots of oxygen, which leads to rot in the field and in storage. Wet soil at harvest also packs onto roots and makes skinning worse.

• Avoid low spots and fields that hold water for more than a day after rain (UMD).
• Plant on ridges or raised beds. The Tennessee guide describes hills or raised rows 6 to 8 inches high, with slips 8 to 15 inches apart in rows 3 to 4 feet apart.
• Break plow pans before bedding, so water can move down and roots can grow deep.
• Keep the bed shape through the season; a slumped bed loses its drainage benefit.

Soil temperature is the other planting rule. The Maryland guide says to plant after all danger of frost, once the soil at 4 inches is above 65°F. Growth is best between 70°F and 85°F. Cold soil stalls slips, invites disease and cuts the season short.

The Clemson guide adds a note for sandy soil: plant on ridges in coastal and piedmont areas for drainage, but skip ridges on sandy soil in the central part of South Carolina, where the soil already drains fast.

▶ Soil moisture meter or satellite map: what each tells you about a field. · 2:11

Salt and irrigation water

Sweet potatoes are moderately sensitive to salt. The FAO crop salt tolerance table gives sweet potato a threshold of 1.5 dS/m soil salinity (ECe), with yield falling about 11% for each 1 dS/m above that. That matters in dry regions that irrigate with well water, in coastal fields and where fertilizer salts build up.

If you irrigate from a well, test the water as well as the soil. Leaching with good-quality water, and banding fertilizer away from the slips, both help keep salt below the threshold.

Chart

Relative sweet potato yield vs soil salinity

% of full yield by soil salinity (ECe, dS/m), threshold-slope model

Fertilizer by soil test

Sweet potatoes need less nitrogen than most vegetables, but they use a lot of potassium. The Maryland guide recommends 50 to 75 lb of nitrogen per acre in total, with half before planting and the rest when vines start to run. Phosphorus and potassium depend on the soil test.

The potassium rate drops steeply as the soil test level rises. On a low-testing soil, the guide calls for 300 lb K2O per acre; on a very high soil, none. That is why a soil test usually pays for itself on this crop.

The Tennessee guide calls sweet potatoes a moderately heavy potassium feeder and says low potassium can hurt root quality. The Texas guide gives a general rate of 50-70-70 lb per acre of N, P2O5 and K2O, and warns that too much soil nitrogen can reduce yield and quality.

Sandy soils hold little potassium, so split applications are safer there. On heavier soils, one preplant pass may be enough. For organic growers, compost and well-rotted manure add potassium and improve structure, but apply them to the crop before sweet potatoes, not just before planting, to avoid extra nitrogen and scurf.

Fertilizer rules differ by state and country. Follow your soil test, the product label and local rules, and ask your extension office or an agronomist for advice on your field.

Chart

Potassium rate by soil test level

lb K2O per acre recommended for sweet potatoes

Rotation, nematodes and soil disease

A good soil can still fail if it carries pests. Root-knot and reniform nematodes cause cracked, knobby roots and lower yield. The LSU AgCenter nematode guide sets the action threshold for reniform nematodes in sweet potatoes at 1,000 per pint of soil, and recommends resistant varieties and crop rotation.

The Alabama Cooperative Extension guide on root-knot nematode describes soil sampling with a probe or shovel and combining resistant varieties, rotation and sanitation. Sandy soils that are best for root shape are also the soils where nematodes do well, so sampling matters most on the best ground.

Rotation rules from the guides:

• Grow sweet potatoes in the same spot only once every three or four years (UT).
• Avoid fields that had sweet potatoes in the past two years, and use long rotations with grains and soybeans (UMD).
• Pick resistant varieties where root-knot or soil rot has been a problem. The Clemson fact sheet lists Covington as resistant to southern root-knot nematode and Fusarium wilt.

Any nematicide or fungicide use must follow the label and local rules. Check with your extension office before you apply.

How to improve a poor soil before planting

Most fields fall short on one or two points. Here is a step-by-step plan, about a year ahead of planting.

1. Map the field. Walk it after rain and mark wet spots, hard pans and sandy ridges. Satellite crop maps from past seasons can show the same weak zones.
2. Soil test by zone. Test pH, P, K, Mg and boron, plus nematodes.
3. Lime in the fall if pH is below 5.8, so it reacts before spring.
4. Fix drainage. Subsoil hard pans, add tile or surface drains, or plan raised beds.
5. Grow a cover crop or grain first to build structure without a big nitrogen spike.
6. Bed in spring once the soil is dry enough to work and the 4-inch soil temperature is above 65°F.
7. Apply P and K by test, half the N before planting and the rest at vine run.

How we checked the numbers

We used extension guides from the University of Maryland, the University of Tennessee, Texas A&M AgriLife, Clemson, Louisiana State University and Auburn (Alabama), plus USDA NASS data and the FAO salt tolerance table. Yield and price figures are USDA estimates for the whole crop, not results from single fields. Where guides disagree, as on pH, we show both ranges and say which guide gives each. We removed yield and pH claims from the earlier version of this page that we could not trace to a source.

Sweet potato margin by field

Good soil raises yield and the share of roots that make a top grade. The calculator below shows how those two numbers, with price and cost, set the margin on one acre. USDA NASS reports the 2025 season-average price received by Mississippi growers at $23.10 per cwt and North Carolina growers at $20.90 per cwt; California’s was $38.40. These are average farm prices for the whole crop, not dealer or retail prices.

Use your own figures. The default values are examples only, set close to break-even, and are not a forecast or a benchmark.

Try the numbers for your own farm below.

Is Kennebec a sweet potato?

No. Kennebec is a white-skinned variety of the common potato, which belongs to a different plant family from the sweet potato. The earlier version of this page mixed the two. The two crops like similar loose, well-drained soil, but common potatoes grow from tubers on underground stems while sweet potatoes form storage roots, and they differ in pests, curing and storage.

For sweet potatoes, the soil points on this page apply to all the main varieties, including Beauregard, Covington and Orleans.

Satellite monitoring of sweet potato fields

Soil differences inside a field show up as patches of weaker vines. Satellite vegetation maps can make those patches visible through the season, so you can sample the soil in the right spots and plan beds, drainage or lime by zone. Farmonaut provides satellite vegetation, soil moisture and weather maps for each field you draw, on web, Android and iOS.

Satellite maps do not replace a soil test. They help you decide where to take one, and they show whether a fix such as lime or drainage made the crop more even the next year.

Related pages on our site: Farmonaut home, the Farmonaut app, Agro Admin app for large farms, satellite and weather API docs, crop loan and insurance tools, carbon footprinting, product traceability and fleet management.

▶ A full walkthrough of satellite crop monitoring and reading NDVI for your own field. · 19:36

If this topic matters to you, read Small Potato Harvester for Sale | One Row & Sweet Potato next.

Related reading on this site: Harvesting Potatoes for Storage: Prevent Dry Rot.

FAQ

What is the best soil for sweet potatoes?

A deep, well-drained sandy loam or loamy sand with pH around 5.8 to 6.2 and moderate organic matter. Avoid heavy clay and fields that hold water for more than a day.

Can sweet potatoes grow in clay soil?

They can, but roots are often smaller and misshapen, and harvest is harder. Use raised beds, add compost the season before, and make sure water drains away fast.

Do sweet potatoes like acid soil?

Slightly. The Maryland and Tennessee guides give 5.8 to 6.2 as ideal, and the Texas guide accepts 5.0 to 7.5. Lower pH helps reduce soil rot.

How much fertilizer do sweet potatoes need?

Modest nitrogen, about 50 to 75 lb per acre in the Maryland guide, and potassium based on a soil test, from 0 to 300 lb K2O per acre. Follow your soil test, the label and local advice.

Should I add manure before planting sweet potatoes?

Apply it to the crop before, not right before sweet potatoes. Fresh organic matter and extra nitrogen can cause scurf, rank vines and lower root quality.

How warm should the soil be to plant sweet potatoes?

Above 65°F at 4 inches deep, after all danger of frost, according to the Maryland guide. Growth is best between 70°F and 85°F.