Best soil for potatoes

Soil Preparation for Potatoes

Potatoes will grow in just about any well-drained soil, but they dislike soggy soil. Because they do all their growing underground, they can expand more easily in loose, loamy soil than in heavy, compacted, clay soil that keeps plant roots from getting the air and water they need.

Working With Your Soil

Heavy soils can dampen your potato-growing enthusiasm, but if you add organic matter (leaves, hay, peat-moss) to the soil, especially at planting time, you’ll be able to ease the hardship of tough earth. When worked into heavy soils with a shovel and rake or tiller, organic matter wedges itself between the tiny soil particles. It works to open up the soil, letting air and water circulate. If you have light, sandy soil that can’t hold water, organic matter also works to help the soil hold moisture better.

Work organic matter into the soil whenever you don’t have a crop growing: before the season gets underway, between crops, or after the harvest. Stockpile compost, leaves and grass clippings for these opportunities.

Using Cover Crops

Another good way to build up organic matter in the soil is to grow “green manure” or “cover” crops to till right back into the soil. Sow quick-growing annual ryegrass, for example, in late summer after harvesting your crops. Then work the crop residues into the soil, sow the annual ryegrass and let it grow until cold temperatures kill it. By planting time the next spring when you’re ready to till the ryegrass into the soil, it will have decomposed well enough to supply your crops with moisture-holding organic matter and the nutrients they need.

If you can’t grow a cover crop, try to spread four or five bushels of compost onto each 100 square feet of potato growing area, and work it into the soil before planting.

Gardeners with clay soil can also incorporate lots of organic matter into the rows where they plant. Covering the seed pieces at planting time with leaves mixed with soil, for example, gives the plants the breathing room they need but couldn’t get if planted in plain soil.

How to plant:

Propagate by division or separation – Grown from seed potatoes — tubers grown the previous season.

Germination temperature: 40 F – Do not plant seed potatoes until soil reaches 40 F.

Days to emergence: 14 to 28 – Sprouts from seed potatoes should emerge in 2 to 4 weeks depending on soil temperature.

Maintenance and care: Potatoes perform best in areas where summers are cool (65 F to 70 F), but are widely adapted.

Potatoes require well-drained soil. (They will rot under prolonged cold, wet conditions.) If your soil is poorly drained or a heavy clay, consider using raised beds. Adding organic matter (compost, cover crops, well-rotted manure or leaves) is a good way to improve soil before growing potatoes. Go easy on organic matter sources high in nitrogen (such as manure) and nitrogen fertilizer as too much nitrogen can encourage lush foliage at the expense of tuber production.

Unlike most vegetables, potatoes perform best in acid soil with pH 4.8 – 5.5. Use scab-resistant varieties with pH above 6.0. Because most other garden vegetables perform best at near-neutral pH, it’s usually not feasible to grow potatoes in their preferred pH range, unless you dedicate one section of your garden to growing just potatoes in rotation with cover crops.

Buy certified disease-free seed potatoes from garden centers or through online or mail-order catalogs for best results. If you save your own seed potatoes, discard any that show any signs of disease. Avoid planting potatoes from the supermarket because they may have been treated with sprout inhibitors. They may also be less vigorous and more prone to disease.

Cut seed potatoes that are larger than a chicken egg into pieces about 1 inch across or slightly larger. Each piece should have at least one “eye” (the bud where the stem will grow from) — preferably two eyes. Egg-sized and smaller tubers can be planted whole.

Traditionally, cut seed potato pieces are allowed to cure for a few days to a few weeks before planting. This is because the cut potatoes need high humidity, plenty of oxygen and temperatures between 50 F and 65 F to heal quickly. If you have excellent, well-drained soil that meets those conditions, you can plant the seed pieces without curing. But if conditions are not right, the seed potatoes will rot in the ground.

A less risky practice is to put about 5 pounds of cut potatoes into a large grocery bag and fold the top closed. Keep the bag at room temperature for 2 or 3 days, then shake the bag to unstick pieces that may have stuck together. Let sit for another 2 to 3 days and then plant.

If you want fast emergence, keep the bag of cut potatoes at room temperature until sprouts appear. Some varieties are slow to break dormancy and benefit from a 2- to 4-week “pre-warming” before planting. Others sprout in just a few days.

Plant about 2 to 4 weeks before your last frost date. The soil temperature should be at least 40 F. Do not plant where you’ve grown potatoes, tomatoes, peppers or eggplant in the past 2 years.

One common way to plant potatoes is to dig a shallow trench about 4 inches deep with a hoe. Place the seed potato pieces with their eyes up (cut sides down) about 8 to 12 inches apart in the trench, and replace soil. Space trenches about 2 to 3 feet apart. Stems and foliage should emerge in about 2 to 4 weeks, depending on soil temperature.

When the plants are about 6 to 8 inches tall, “hill” the potatoes by hoeing soil loosely around the base of the plants to within about an inch of the lower leaves from both sides of the row. Repeat in about 2 to 3 weeks. You may want to make additional hillings, gradually building a 6- to 8-inch ridge down the row. (Hilling keeps the developing potatoes from being exposed to sun, which turns them green and bitter. Green potatoes contain a chemical, solanine, which is toxic in large amounts.)

Alternatively, snuggle seed pieces shallowly into the soil and cover with a thick layer of clean straw or other weed-free mulch. Add more mulch as needed to keep light from reaching potatoes. (A foot or more of mulch may be required.) Tubers grown this way can be easily harvested by pulling back the mulch after the plants die.

A third method if you have excellent potato-growing soil is to plant seed potatoes 7 to 8 inches deep and skip hilling or deep mulching. The potatoes are slower to emerge, but this method requires less effort during the growing season. Deep planting is not good in cold, damp soils and it requires more work to dig the potatoes at harvest.

Potatoes need at least 1 inch of water per week from either rainfall or deep watering. Mulching helps retain moisture. Keeping the soil from drying out also helps reduce scab.

Use row covers to protect from Colorado potato beetles, leaf hoppers and flea beetles. Crush the yellow eggs of Colorado potato beetles on the undersides of leaves. Remove adults by hand.

Pests: Colorado potato beetles – Hand pick beetles, eggs and larvae.

Aphids – A hard stream of water can be used to remove aphids from plants. Wash off with water occasionally as needed early in the day. Check for evidence of natural enemies such as gray-brown or bloated parasitized aphids and the presence of alligator-like larvae of lady beetles and lacewings.

Flea beetles – Use row covers to help protect plants from early damage. Put in place at planting and remove before temperatures get too hot. Control weeds.

Leaf hoppers
Wash small nymphs off with a hard stream of water.

Diseases: Early blight and Late blight – Use certified seed. Avoid wetting plant foliage if possible. Water early in the day so abovegrounds plant parts will dry as quickly as possible. Avoid crowding plants. Space apart to allow air circulation. Eliminate weeds around plants and garden area to improve air circulation. In autumn, rake and dispose of all fallen or diseased leaves and tubers. Locate new plants in a part of the garden different from previous year’s location. Resistant or moderately resistant varieties include Allegany, Elba, Rosa and Sebago.

The fungus that causes late blight has recently become a major threat to home gardens and commercial growers because of the migration of new strains (genotypes) into the United States. The disease can readily spread from home gardens to commercial fields. Verification of a late blight diagnosis and implementation of prompt control measures are highly recommended. The newly arrived strains are more aggressive than previous strains. Cultural control measures such as those listed above may not adequately control these new strains.

Scab – Use certified seed. Locate new plants in a part of the garden different from previous year’s location. Lower soil pH to 5.2 with sulfur. Plant resistant varieties: Chieftan, Norland, Russet Burbank, Russet Rural and Superior.

Viral diseases – Use certified seed. Control aphids.
Sweet potatoes require warmer temperatures and a longer season.


Crop characteristics

Potatoes produce a fibrous root system. These roots are at best no more than 24 in long. Thus potatoes are shallow rooted compared to cereals for example, which can root to at least 47 in depth. As a result, potatoes are often unable to exploit nutrients and soil moisture at depth within a soil profile.

While root growth occurs when soil temperatures are between 50 to 95˚F, best, most active root development is at soil temperatures of between 59 and 68˚F.

Leaf (haulm) growth occurs at temperatures of between 45 to 86˚F, but optimal growth is at around 68 to 77˚F. Optimum temperatures for stolon growth are similar.

The potato tuber is an enlarged portion of the stolon. The initiation of this tuber is triggered by short day lengths (photoperiods), and involves growth hormones. The colder the soil temperature, the more rapid the initiation of tubers and the greater the number of tubers formed. The optimum soil temperature for tuber initiation is 59 to 68˚F.

Under these conditions, the potato plant will have short stolons and shoots. Longer day lengths delay tuber initiation and favor the growth of the stolon and shoot.

Low nitrogen and high sucrose levels in the plant favor the formation of more tubers. Once formed, tubers grow rapidly, reaching a maximum rate of up to 1,250 lb/ac/day in temperate climates. Late varieties seem to be more sensitive to long day lengths or high temperature conditions.

Physiological ageing

By planting sprouted seed, crop growth can be advanced. The magnitude of this response and its effect on increasing crop yield is related to the physiological age of the seed at planting.

Seed storage temperature is the key to controlling physiological aging. Raising storage temperature above 39˚F promotes the break in dormancy and the growth of sprouts.

The accumulation of the number of day degrees from this break of dormancy governs the physiological age of the tuber at planting.

Different varieties vary in the number of day degrees needed to age to a desired level prior to planting. Old aged tubers are advantageous when planting early varieties or when the growing season is short.

Tubers that have been minimally aged are suited to long growing seasons where it is desirable to keep the potato growing to achieve maximum yields. When planting sprouted seed it is necessary to control sprout numbers and length (maximum 0.8 in) to ensure optimum growth according to plant spacing, and to ensure minimal sprout damage when planting.

Soil type and management

Potatoes are grown on a range of soils varying from sands to clay loams, all with different water holding capacities. An ideal potato soil is well structured, with good drainage to allow proper root aeration, tuber development with minimal root disease infestation.

Potatoes prefer soils with a pH of 5.5 to 7.0 and low salinity. However, in practice potatoes are grown in soil pH’s from 4.5 to 8.5 and this has a distinct impact on the availability of certain nutrients. Extreme soil pHs should be adjusted where it is practical to do so.

At lower pH values potatoes can suffer from aluminum and other heavy metal ion toxicity, as well as restricted P or Mo availability.

At pH values above 7.5, nutrient availability, in particular of phosphorus and the micronutrients, can be reduced, even though high total amounts of these elements may be present in the soil. Liming can ameliorate undesirable, low pH values although care must be taken to ensure that the lime is applied at least 6 months before the potatoes are to be planted. Potatoes are more prone to common scab when grown in high pH soils.

Ridging and hilling

Potatoes are often planted in ridges or hills because this ensures a well-drained, well-aerated environment for strong crop growth.

In colder soils, ridging raises the soil temperature allowing quicker germination and early growth.

When side dressing with fertilizer, the remaking of the ridge allows the incorporation of the fertilizer into the soil around the tuber.

Ridging also maximizes coverage of the developing tuber, so as to prevent greening and ensure tubers are well shaped, more evenly sized and at lower risk of damage.

Water management

Potatoes have a high water requirement – roughly 1 in/week during bulking. Thus, for high yields irrigation is usually beneficial.

Water management is essential to minimize tuber problems. Maintaining a moist soil in the ridge at tuber initiation can minimize common scab development. Later in the season, excessive water around the tuber encourages powdery scab and lenticel growth.

Fluctuations in soil moisture status within the ridge will lead to uneven tuber bulking, malformed tubers and growth cracks. Even a 10% variation in soil moisture status can be critical. For this reason, when using drip irrigation systems, the tape should be placed in the top of the ridge.

Canopy management is also critical to maximize efficient use of water. Growers in high temperature environments need to ensure quick canopy closure to minimize water loss due to evaporation from the soil surface.

Crop Protection

Early blight (Alternaria solani) and Late blight (Phythophthora infestans) are major diseases that can have a devastating effect on the crop.

Early blight is a problem, particularly in early varieties, spreading from the leaf to young tubers. It can result in severe defoliation, but, if managed correctly, plants can grow away from infestations.

Late blight occurs under cool moist conditions and if left uncontrolled, quickly spreads to the tuber resulting in significant tuber browning and rot.

A range of mosaic viruses also affect potato leaf growth, leading to a drop in yield. Control of the aphid or other carrying vectors, minimizes damage.

In addition, various free-living nematodes and/or potato cyst nematodes can cause significant damage. Wide rotations are needed in some countries to minimize crop loss.

Potato Bed Preparation: Prepping Beds For Potatoes

Incredibly nutritious, versatile in the kitchen, and with a long storage life, potatoes are one of the must haves for the home gardener. Properly preparing a potato bed is the key to a healthy, prolific potato crop. There are a number of potato bed preparation methods. What kind of potato seed bed preparation do you need to do to guarantee a bumper crop? Read on to learn more.

Prepping Beds for Potatoes

Properly preparing beds for potatoes is of primary importance. Neglecting potato bed preparation may result in inferior crops. Improperly prepared beds may be predisposed to soil compaction and poor aeration and drainage, three things that potatoes abhor.

Consider what type of previous crop was in the bed. Be sure that any debris has been well composted and avoid planting in the area if it was recently planted with any other Solanaceae members (nightshade family) to reduce the risk of passing on bacteria or virus pathogens. Instead, plant the area with a legume crop and move to another area for potato bed planting.

Potato bed planting should take place in rich, loose, well-draining, but moist, soil with a slight acidity of pH 5.8-6.5. One month to 6 weeks prior to planting, loosen the soil down to a depth of 8-12 inches and add 3-4 inches of compost or a complete organic fertilizer with a NPK of 1-2-2 (5-10-10 is acceptable) at a rate of 5 pounds per 100 square feet.

In lieu of the previous, you may also amend the soil with 3-4 inches of composted steer manure or one inch of composted chicken manure, 5-7 pounds of bone meal per 100 square feet and a smattering of kelp or seaweed meal. When in doubt of your soil’s nutritional needs, contact your County Extension office for assistance. When prepping beds for potatoes, remember they are heavy feeders, so adequate nutrition at the outset is crucial.

Till all the amendments into the soil and turn several times. When preparing a potato bed, rake the bed smooth, removing any large stones or debris. Water in well to test for soil drainage; if the bed doesn’t drain well, you will need to add organic matter, clean sand or even commercial soil. Drainage is of paramount importance. Potatoes will rapidly rot in sodden soils. Many people grow potatoes in a hill or mound which will also ensure that plants are above any standing water. Elevate beds 10-12 inches in this case.

Additional Potato Bed Planting

If you don’t want to take the time preparing a potato bed, you may also choose to grow your potatoes by using straw or mulch. Simply loosen the soil so the roots get good aeration, food and irrigation. Place the seed potato atop the soil and cover with 4-6 inches of straw or mulch. Continue to add 4-6 inches to cover new leaves and shoots as the plant grows. This method makes for an easy and very clean harvest. Just pull the mulch back, and voila, nice clean spuds.

Another easy potato bed preparation involves using the mulching method above, but in a container or bin instead of on the soil surface. Make sure the container has drainage holes; you don’t want to drown the tubers. Be sure to water more frequently than if you planted the potatoes in the garden, as container grown plants dry out more rapidly.

Now that your potato seed bed preparation is complete, you can plant the seed potatoes. The earliest you should plant is two weeks before the last frost date in your area. Soil temps should be between 50-70 F. (10-21 C.).

Taking time when prepping beds for potatoes will ensure healthy, disease-free tubers that will feed you and your family all winter long.

Tracking Down the Best Soil for Potatoes

Turning Your Soil Around

While soil transformation isn’t quick, it’s relatively easy. If you can apply a combination of organic and natural tactics and give yourself an adequate timeline to do so, you can make that heavy block of dirt on your property potato-ready by the time the growing season comes around.

One of the big organic steps you can take is to add manure to your garden. We’re not talking about scooping up a fresh pile of animal poop to your dirt here. Rather, it’s best that you mix the dung with a compost made from organic elements, such as bone meal or blood meal.

This dynamic duo may not look all that attractive, but when they’re combined, they can add nutrients that can loosen the soil and allow plants like to potatoes to thrive. This, then, will theoretically produce results that will make you pretty happy.

Of course, using the manure/compost combo isn’t a matter of just leaving piles of the stuff on top of the dirt. It must be gently tilled into the soil prior to spring planting. Ideally, you’ll want to do this during the fall, as this will give the combo plenty of time to break down and add the much-needed give and nutrients.

A Little Help

Making your own soil can be time consuming, and a bit frustrating if your thumb hasn’t quite turned green yet. However, there are plenty of ready-made enhancements that can speed up the process and eliminate a couple of steps.

Some of the material you can purchase is ready-made organic compost that can be tilled directly into your soil. In some cases, this combo will add manure from various animals into the mix, so you won’t have to worry about having to deal with the possibility of incorporating dung into the mix.

Some of the soil you can pick up for your potatoes is straight up topsoil, designed to mix in with what you already have. The presence of this topsoil, when tilled, will naturally work in concert with the heavy clay soils to loosen them up, thus allowing for proper drainage.

Our Recommendation: Fox Farm Ocean Forest Soil

Adding a proper dosage of compost to your dirt is the best way to get it to turn from heavy to light. However, making compost yourself can be a messy, icky task that, if you’re just starting to learn the ins and outs of gardening, may turn into a massive turnoff.

This is why the Fox Farm Ocean Forest Soil works as a substitute. Its eclectic mix of materials includes things like earthworm castings, crab meal, and bat guano. This latter component provides the blend with an all-important manure ingredient that a lot of gardeners value during the growing season.

A soil product like this one also provides you with a good benchmark of how to go about building your own compost, should you decide to take that proverbial next step. The ingredients are a small sample size of the materials that can go into compost.

Some of the ingredients you can use may not look too surprising, like pine needles, dried leaves, seaweed, and kitchen scraps. Others may be a little surprising to the novice, such as coffee grounds and shredded cardboard. Yet these components can break down and coalesce into a wonderful mess of nutrients that will turn your soil into a gardening powerhouse.

Once this special transformation is complete, your soil will be able to embrace the potato plant and give it what it needs to thrive. It’s not the most glamorous of transformations you can make in your garden, but after you reap the benefits of a successful harvest, you may find it to be the most rewarding one.

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