Fertilizer For Potatoes: How, When, and What to Feed Potato Plants

Wondering what’s the best fertilizer for potatoes? Fortunately, there are a few different things you can add to your soil to help your plants thrive.

Fertilizer for potatoes generally starts with applying a balanced all-purpose slow-release organic fertilizer about a week before the seed potatoes are planted. You may also wish to adjust the pH to between 6.0 and 6.5 using sulfur or garden lime. Several weeks after planting, side-dress the sprouting plants with a calcium-rich fertilizer. You may also wish to apply a quick-acting water-soluble potato fertilizer rich in phosphorus and potassium on a frequent basis in nutrient-deficient soils. Stop fertilizing potato plants about a month before harvesting the tubers.

Read on to learn all about fertilizer for potatoes!

fertilizer for potatoes

Fertilizer For Potatoes: The Basics

There are many different types of fertilizer available for potatoes, including organic and synthetic options. Some popular organic fertilizers include compost, manure, and seaweed extracts. Synthetic fertilizers are also widely used in conventional gardens and farms to boost potato growth.

Key Nutrients For Potato Plants

All potatoes need nitrogen, phosphorus, and potassium to grow well. These are the three main numbers you’ll see on bags of fertilizer (e.g., 10-10-10). Nitrogen is necessary for foliage growth, phosphorus encourages root development, and potassium helps the plant resist disease and pests. Avoid using fertilizers that are higher in nitrogen than in phosphorus as this can lead to a large leafy plant without much tuber development.

Potato plants also need quite a bit of calcium to thrive. Young plants are generally fertilized with calcium nitrate or similar calcium-rich fertilizer.

When To Fertilize Potato Plants

When it comes to timing your fertilizer application, be sure to start early! Fertilizer for potatoes should be applied a week or two before planting the potato tubers. This will give the fertilizer time to break down and be absorbed by the soil before the plants start growing. Pre-fertilizing is usually done with a general all-purpose vegetable garden fertilizer like a slow-release organic granular fertilizer. This can be sprinkled on top of the soil or worked into the top 6″ of soil prior to planting.

If you’re using a slow-release fertilizer, you may not need to fertilize again until several weeks after planting. However, if your soil is very nutrient-deficient, you may wish to apply a water-soluble fertilizer frequently throughout the growing season. Liquid fertilizers deliver a quick dose of nutrients to the plants in an easily accessible manner.

“Water with an organic liquid fertilizer every few weeks to encourage strong growth.”

GrowVeg: The Beginner’s Guide to Easy Vegetable Gardening, by Benedict Vanheems

A calcium-rich fertilizer is usually applied to the potato plants 2-4 weeks after planting. This addition of calcium just as the plants are sprouting and being hilled provides a key nutrient for plant cell development just as growth is increasing.

boxes of potato fertilizer and seed potatoes at garden center

How To Fertilize Potato Plants

Before fertilizing potato plants, it’s important to test your soil and determine which nutrients need to be added. This can usually be done with a home soil test where you collect the sample and ship it to a proper soil testing laboratory.

After you’ve determined which nutrients need to be added to your soil, you can begin fertilizing potato plants. If you’re using a granular fertilizer, simply apply it to the soil around the plants according to the manufacturer’s directions. For liquid fertilizer, mix it with water and apply it to the soil with a watering can or hose-end applicator.

It’s important not to over-fertilize potato plants as this can actually damage the plants and reduce yields. If you’re unsure how much fertilizer to use, it’s always better to err on the side of caution and use less rather than more.

Whether you’re planting potatoes at home or in a commercial setting, it’s crucial to fertilize them properly in order to ensure optimal growth. Start by reading the labels on fertilizer bags carefully to determine which product is best suited for your needs, and then use the appropriate application methods to provide your potato plants with all the nutrients they need!

Mary Jane Duford
Mary Jane Duford

Mary Jane Duford is a gardening expert and founder of Home for the Harvest. She's also an engineer and certified permaculture garden designer. Mary Jane has been featured by publications such as Real Simple, Mother Earth News, Homes & Gardens, Heirloom Gardener, and Family Handyman.