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Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16

Grow bigger potatoes with our 8-16-16 formula. Low nitrogen, high P-K for maximum tuber yield. Application rates & tips from Old Cobblers Farm.

Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer

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OUR STORY

This 8-16-16 potato formula is a custom-blended granular fertilizer produced by Green Mountain Fertilizer. The intentionally low 8% nitrogen prevents the excessive vine growth that delays tuber initiation and reduces yield. The high 16% phosphorus from DAP addresses potatoes' critical need for early root and tuber development—phosphorus must be placed in the root zone because it is immobile in soil. The 16% potassium drives starch accumulation in tubers, determining specific gravity, cooking quality, and storage longevity. Micronutrients address boron, zinc, and manganese needs. This is the same formulation as Old Cobblers Farm™ 8-16-16 Multi Purpose Fertilizer.

NPK

8-16-16

Type

Non-Organic

Derived From

Urea, Diammonium Phosphate (DAP), Potassium Chloride (Muriate of Potash), Silicon Dioxide. Includes micronutrients.

Best For

Brand

Wicked Growth

NPK Breakdown

N

Provides a restrained 8% nitrogen (from urea) to support top growth without promoting excessive vine or leaf production at the expense of root and tuber development

P

Delivers a strong 16% phosphorus (from diammonium phosphate) to drive deep root formation, tuber initiation, flower production, and overall below-ground development

K

Supplies 16% potassium (from muriate of potash) to maximize tuber size, starch content, fruit firmness, skin quality, and storage life

What Is It ?

Potato fertilizer (8-16-16) is a tuber-focused granular blend specifically designed for potato production. Potatoes are fundamentally different from most garden crops—their harvestable product grows underground, meaning the fertilizer strategy must prioritize root and tuber development over foliage. This formula's low nitrogen-to-high phosphorus-potassium ratio reflects what potato research shows: excessive nitrogen produces large vines but delays tuber set and reduces yield, while strong P and K drive earlier tuber initiation, larger tubers, higher starch content, and better storage quality. The 16% phosphorus from diammonium phosphate (DAP) feeds the extensive root system potatoes need. The 16% potassium from muriate of potash is essential for starch synthesis, tuber skin quality, and disease resistance. Micronutrients are included for complete nutrition. This is the same formulation as Old Cobblers Farm™ 8-16-16 Multi Purpose fertilizer. Manufactured by Green Mountain Fertilizer in Milton, Vermont.

When To Apply ?

Open furrows 4-6 inches deep, apply fertilizer at 1-2 lbs per 100 sq ft banded 2-3 inches below and to the side of where seed pieces will be placed. Never let fertilizer touch seed pieces directly. At hilling time (plants 6-8 inches tall), side-dress with 0.5 lbs per 100 sq ft and hill soil over it. For commercial production, apply 400-800 lbs per acre with 60-70% at planting and 30-40% at hilling. For grow bags, mix 2 tablespoons into the bottom half at planting.

How to Apply ?

1. Soil Test

Test soil before planting for existing P and K levels. Potatoes are heavy feeders of phosphorus and potassium.

2. At Planting

At planting, band 1–2 lbs per 100 sq ft in the furrow, 2–3 inches below and to the side of seed pieces.

3. Avoid Contact

Do not place fertilizer in direct contact with seed pieces. Contact causes burn and reduces germination.

4. At Hilling

At hilling (plants 6–8 inches tall): side-dress with 0.5 lbs per 100 sq ft along the row.

5. Hill Over

Hill soil over the side-dress application to bury nutrients near developing tubers.

6. Water In

Water thoroughly after each application to dissolve granules and activate nutrients.

7 Avoid Contact

Do not place fertilizer in direct contact with seed pieces. Contact causes burn and reduces germination.

How To Store

Wear protective gloves and eye protection during handling. Avoid breathing dust. Wash hands thoroughly after handling. Store in a cool, dry, well-ventilated area. Slightly reactive with oxidizing agents, metals, alkalis, and moisture. Phosphorus runoff poses a threat to water quality—do not apply near waterways. Check local phosphorus fertilizer restrictions. Keep out of reach of children and pets.

FAQs

1. What is the best fertilizer for seed potatoes?

The best fertilizer for seed potatoes provides high phosphorus and potassium with moderate nitrogen. An 8-16-16 ratio is ideal because the elevated phosphorus (16%) promotes rapid root establishment and tuber initiation, while the high potassium (16%) improves tuber size, density, skin quality, and storage life. The moderate nitrogen (8%) supports healthy foliage without encouraging excessive vine growth at the expense of tuber production. Apply at planting time and side-dress during tuber formation for maximum yields. Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 is purpose-built for bigger, healthier potato harvests.

2. When should I fertilize potatoes?

Fertilize potatoes at three key stages: first at planting by mixing fertilizer into the trench or hill soil, then when plants are 6–8 inches tall as a side-dress application, and again at mid-season when tubers are actively forming and sizing. Avoid heavy nitrogen applications late in the season, as this promotes continued vine growth instead of tuber maturation. Stop fertilizing about 2–3 weeks before harvest to allow skins to set. Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 delivers the right nutrients at each critical stage of potato development.

3. How much fertilizer per potato plant?

For individual potato plants, apply 1–2 tablespoons of 8-16-16 fertilizer per plant at planting, mixing into the soil around the seed piece. For row planting, apply 2–3 pounds per 100 feet of row. For raised beds, broadcast 2–3 pounds per 100 square feet and incorporate into the top 6 inches of soil before planting. Side-dress with half the initial rate when plants reach 6–8 inches tall. Always keep fertilizer a few inches away from seed pieces to prevent burn. Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 is easy to measure for precise, consistent feeding.

4. Why do potatoes need high phosphorus and potassium?

Potatoes are underground crops that depend heavily on phosphorus and potassium for tuber development. Phosphorus drives root growth and tuber initiation — without adequate phosphorus, plants produce fewer and smaller tubers. Potassium is essential for tuber sizing, starch accumulation, skin development, and post-harvest storage quality. Together, these nutrients ensure that the plant channels maximum energy into producing large, dense, well-formed tubers rather than excessive above-ground vine growth. Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 delivers double the phosphorus and potassium of standard balanced fertilizers.

5. Can I use 10-10-10 on potatoes instead of 8-16-16?

You can use 10-10-10 on potatoes, but 8-16-16 is a better match for their specific nutritional needs. Potatoes prioritize phosphorus for tuber initiation and potassium for tuber quality over nitrogen for vine growth. 10-10-10 provides relatively more nitrogen and less phosphorus and potassium, which can encourage leafy vines at the expense of tuber production. If 10-10-10 is all you have, supplement with additional 0-46-0 (triple superphosphate) and 0-0-60 (muriate of potash). Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 eliminates the guesswork with a potato-optimized formula.

6. How do I grow bigger potatoes?

Growing bigger potatoes requires consistent moisture, proper hilling, good drainage, and the right fertilizer ratio. Use a high P-K formula like 8-16-16 to maximize tuber development. Hill soil around plants as they grow to provide more room for tubers to form. Maintain even moisture — drought stress causes knobby, misshapen tubers. Space seed pieces 10–12 inches apart to reduce competition. Remove flowers to redirect energy into tubers. Harvest after vines die back for maximum size. Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 provides the phosphorus and potassium that drive tuber sizing.

7 What varieties of potatoes can I grow with this fertilizer?

Old Cobblers Farm™ Wicked Growth Seed Potato Fertilizer 8-16-16 works with all potato varieties, including russets (Russet Burbank, Norkotah), reds (Red Pontiac, Norland), yellows (Yukon Gold, German Butterball), fingerlings (French Fingerling, Russian Banana), purples (Purple Majesty, All Blue), and whites (Kennebec, Superior). The 8-16-16 formula supports tuber development regardless of variety, whether you are growing for baking, boiling, roasting, or storage. It also works well on sweet potatoes, which share similar phosphorus and potassium needs.