Fertilizer Recommendation for Solanum Tuberosum

About Potatoes

• Potatoes are best grown from certified seed potatoes, small tubers grown by commercial growers under sterile conditions and guaranteed to be free from disease, especially scab. These seed potatoes produce above-ground vines and form the tubers we know as potatoes underground. Potatoes grow best in loose, organic soils with excellent drainage. Small "new" potatoes can be harvested throughout the growing season by digging carefully by hand near the vines until you find a tuber, but the main crop is harvested two weeks after the vines die back naturally in late summer or fall.

Fertilizer Needs

• Both commercial fertilizers and composted manure are suitable for potato plants. Animal manures must be well composted and ideally should be tilled into the soil the fall before planting. Don't use manure if scab is a problem in your area. Choose a commercial fertilizer with a 1-2-2 ratio, such as 5-10-10 or 8-16-16. Always follow package directions for the proper amount of fertilizer to apply per square foot, as too much fertilizer burns plant roots. Potatoes are fertilized when planted and then after the plants are up and growing.

How to Apply

• The most efficient way to apply fertilizer to potato beds at planting time is to spread it in continuous bands 2 to 3 inches to the side and just below the seed potatoes. This puts the fertilizer where it's needed most, close to the developing roots. You can also broadcast the fertilizer over the planting area and till it into the soil before planting; follow the product directions for the proper amount to use per square foot.

  After the potato plants are 4 to 6 inches tall, inspect the plants. If growth is not as vigorous as expected or if the foliage is pale or yellowish, feed the plants again with 2 to 3 pounds of fertilizer per 100 feet of row, spreading it 6 to 10 inches to the side of the row. Potatoes grown in lean, sandy soil are more likely to need extra fertilizer than those grown in rich loam.

A Note About Soil pH

• The acidity or alkalinity of soil, referred to as the soil pH, affects any plant's ability to absorb nutrients through its roots. A pH of 7.0 is considered neutral; below that is acid and above that is alkaline or "sweet." The best soil pH depends on the crop you're planting. For potatoes, the pH should be acid, between 5.0 and 5.5.

  In addition, potatoes grown in nonacidic soil are susceptible to scab, a bacterial disease that lingers in the soil from year to year. Do a soil test annually to check the pH in the area where you want to plant potatoes. Use agricultural sulfur to lower the soil pH at the rate recommended by your local extension service; the amount will vary depending on your soil's structure and content. If scab is a problem in your area, use scab-resistant varieties such as "Superior," "Yukon Gold" and "Russet Burbank." Rotating the potato crop to different areas each year also helps control the disease.